Berkeley Mods pictorial Episode 1

[Froggystyle]

As some of you know, I have been having a hell of a time getting OTR to hook up out of the hole. I have a lot of power, but a lot of boat as well. The short history is this...
When I purchased my new Ultra 21XS last year, I was the first person to spec a Berkeley jet in over five years. I have had Berkeley's in everything I have owned up to this point, and saw no reason to change. In addition, I felt with the high-performance nature of the engine, we needed to go with a race-proven platform.
It also turns out I am the first person in five years who can't get his Ultra to holeshot. I started investigating the differences between a Berkeley 12JG with a stock machined shoe and ride plate, and after talking to several people about the problem, including Mike Harlan from Ultra Performance, John West of Ultra, Dave Jones of Agressor, Ron Gordon from American Turbine (Dominator) and Mike from CP I have concluded that my intake is considerably smaller than any of the earlier versions, and it is as a result of the shoe design and cut. From the forward edge of where the intake grate bolts in to the rearward edge of the shoe is 13.25 inches. I decided to open it up a little, and take pictures along the way to show everyone.
This first pic is of the shoe mounted in the intake. Sorry about the quality of the shot, but you get the idea. The edge of the shoe is nowhere near the edge of the intake, and is in fact off by more than 7/16 of an inch.
http://www.highperformancecars.com/froggystyle/before_mounted.jpg
This next pic shows with some lines and stuff where the problems exist. The top line shows the lack of blend with the intake, and the blue area shows how far it does not blend by. Everything blue is a step in the intake, completely blocking and disturbing the water flow. In addition, the slope was far shallower than the intake slope, so it closed off the intake opening needlessly. Lastly on this picture, you can kindof see how poorly machined this piece was. Lots of machining grooves apparant.
http://www.highperformancecars.com/froggystyle/before_mounted_diagram.jpg
After marking the protruding area with a marker, I removed the ride plate and shoe and further colored the area with a paint pen, to show me how much I had to grind off. The area in orange is this large blockage I mentioned in the last picture. This is a significant amount of intake lost at the most crucial point. To get my bottom curve right, I used a straight edge in the intake and measured the radius of a matching circle. I drew this onto a piece of paper and used the grinder until the aluminum shoe edge matched the line. You can see here even better how badly off the machining was. It isn't even straight! The curve of the intake is exact, but this piece was off center by about 3/8" and it shows with how heavy the orange is on the left side of the piece and narrow it is on the right. This is just a poorly machined piece.
http://www.highperformancecars.com/froggystyle/before_bench.jpg
Here is a picture of how much metal was getting removed during the process.
http://www.highperformancecars.com/froggystyle/in_process.jpg
Here is an "after" pic of the shoe on the bench
http://www.highperformancecars.com/froggystyle/after_bench.jpg
Since it is hard to tell how much metal was actually removed, and how much steeper the ramp became to match the intake slope, I colorized and superimposed the modified version on top of the stock version. You can see in this picture clearly how much was taken off.
http://www.highperformancecars.com/froggystyle/superimpose.jpg
This is the worst picture of the bunch, but you can see how much better this modified shoe blends with the intake. Much cleaner, and a straight edge run down the ramp of the intake confirms that the slope is exactly right. A little cleanup with a half-round file and it was smooth as silk.
http://www.highperformancecars.com/froggystyle/after_mounted.jpg
I will test the new mod this weekend locally, and let everyone know how it went. The next episode is switching from a stock "A" impeller to a highly detailed "A" impeller and adding a billet stuffer.
Squirts up!
[ August 05, 2002, 03:14 PM: Message edited by: Froggystyle ]

[HBjet]

Interesting. Froggy, your shoe was a stock machined shoe from Berkeley, and that is how they come. The rigid slope of the shoe wouldn't effect you that much. If you don't have one, I would first install a cav. reducer that is detailed. You will be amazed on how much that one item will help. For your shoe, I would have a cut back shoe made to you can get a littl more lift out of the boat, therefore more MPH.
http://home.pacbell.net/jmcclure/TshoeBCshoe1.jpg
Tapered (a 0.5 deg taper, left), and Backcut (a 2 deg backcut, right)
Let us know how your tests turn out.
HBjet

[Froggystyle]

I don't know if you checked lately, but lift is not what this boat needs. wink It is way out of the water already because of the droop and ride plate. Intake pressure is. I am cavitating the pump out of the hole very badly. At full speed I only have between 15lbs and 25lbs of pressure in the intake, depending on grate design, and out of the hole down to damn near nothing. In addition, this shoe is a full 1/4" below the keel line. Most are above, and we still can't get it to hook up. This small intake size is most likely the culprit. A backcut may or may not result in more speed, but I would gladly give up top speed to gain some holeshot.
Regarding the DPS impeller, that will probably be forthcoming, but I fear that it will be masking a greater problem, that if resolved would show even more performance when the DPS impeller is added. We are doing this systematically, and wish to catalog all changes for future reference.
Dave Jones from Agressor wants to be involved in the resolution of this problem as well, and we are going to work together to try to fix the holeshot issue. I have a new impeller coming from him as you know, and I want to make sure he has all of the opportunity to smoke this Berkeley setup I am currently running. I am optomistic!
Squirts up!
[ August 05, 2002, 04:21 PM: Message edited by: Froggystyle ]

[RiverDave2]

http://www.highperformancecars.com/froggystyle/after_bench.jpg
Wes, This picture is bothering me quite a bit. I'm going to be at the shop doing all of my machining this weekend (including the things that I've been laggin on for you) If you want to swing by and make that thing a little closer to circular I'd be more then happy to try and help out.
RD

[Froggystyle]

Thanks Dave, but unfortunately, the shoe is not quite square with the pump either, so it will not look square with the bolt holes. This is the result of actually scribing the intake hole with it in place. As you can see, it matches perfectly with the intake. It is unfortunate, and shows a lack of either quality control on Berkeley's part (CP performance) or Hardin Marine (CP Performance) who made the shoe and ride plate.
What I would like to do is build a new ride plate, as mine has a swallow tail on it that noone who knows what they're doing can figure out why. I want to build another plate with a square edge. I probably need a drill press and countersink bit for that....

[Licketty Split]

The draw back of sand casting.. Mine is sloght ly off too
Great post thx

[miller19j]

Froggy,
I am planning on redoing my pump this winter and would be interested in how your modification affects the performance of your boat.
Do you have any quantitative numbers for the acceleration before your mod? Did you do some timed trials with a GPS or a Speedo?
Please keep us updated
Miller19j

[ChetCapoli]

Froggystyle
I want to make sure he has all of the opportunity to smoke this Berkeley setup I am currently running. I am optomistic!
Squirts up!You know froggs, maybe i was wrong about you. This thread surprised the hell out of me. Your actually willing to work and try other stuff to go fast and not just stick to the same old, same old. You realize there just might be something out there to make your ride better and faster. Hats off to ya!
Chet

[HBjet]

Hey Chet, so how did the boat run, a lot of us are waiting to here if all that bottom work paid off. Weren't you at 80mph before the work, what did it do now? Thanks
Froggy, I've been thinking about this a lot, and that little step from your shoe to your intake shouldn't be causing you to cavitate. What impeller do you have and what condition is it in? can you post a photo of it? Thanks
HBjet

[OmegaBitch2]

How about trying an inducer?? Ive heard that they really help,especially with B/C impellers.That as well as smaller pump inlets.The opening on my YJ/AT energizer is big enough that you can stick a football up inside it, just finished building a new loading grate for my combo.Hoping to try it out this weekend.

[miller19j]

HBjet:
Froggy, I've been thinking about this a lot, and that little step from your shoe to your intake shouldn't be causing you to cavitate. What impeller do you have and what condition is it in? can you post a photo of it? Thanks
HBjetHB I am not an expert on fluid dynamics but it seems to me that Froggy is on the right track. If he does have a lip there as big as it appears in the pictures it would disrupt flow. Causing the linear flow of water to become disturbed and the possibility of cavitation.
I am eager to see how his modification affects his performance
Miller19j

[Froggystyle]

I'm not sure I would call 7/16" a "little lip". that is some serious disturbance. And, that is EXACTLY what causes cavitation.
I have a brand new Aluminum A2 in there right now, with a billet stuffer, and running .015 clearance. It doesn't get any tighter! No, I don't have a picture of it. If you have seen a new Berkeley impeller though, it looks just like it.

[Froggystyle]

miller19j
HB I am not an expert on fluid dynamics...[/QB]Neither is Randy...

[HBjet]

Froggystyle:
I'm not sure I would call 7/16" a "little lip". that is some serious disturbance. And, that is EXACTLY what causes cavitation.Really? and how did you discover this?
Froggystyle:
If you have seen a new Berkeley impeller though, it looks just like it.I have seen a new Berkeley Aluminum impeller and it didn't look too good (Even an Aggressor Aluminum looked better) I even told the owner of Berkeley when I met him that his Aluminum impellers weren't perfect. He said he knows. For stock power, they will be fine. For Froggy's boat a stock impeller wouldn't be good enough for the power he is pushing.
Hmmm, could that be why your cavitatiing out of the hole?
[ August 07, 2002, 11:20 AM: Message edited by: HBjet ]

[HBjet]

Froggystyle:
miller19j
HB I am not an expert on fluid dynamics...Neither is Randy...[/QB]Neither is Wes!

[HBjet]

A 7/16" step will not cause your boat to cavitate when getting on plane. That is your problem right? The faster you go, the more and more that step will effect you, not the other way around. Since your pump runs fine on plane, and through the big end, it wouldn't cavitate from that little step when getting on plane. I think it's your impeller. Can you post a photo of it?
HBjet
[ August 07, 2002, 11:26 AM: Message edited by: HBjet ]

[565edge]

Froggy you might be going in the right direction,if not atleast you tried,i would try a inducer,if you dont like i will buy it from you?let us know how it turns out? wink

[miller19j]

HBjet:
A 7/16" step will not cause your boat to cavitate when getting on plane. That is your problem right? The faster you go, the more and more that step will effect you, not the other way around. Since your pump runs fine on plane, and through the big end, it wouldn't cavitate from that little step when getting on plane. I think it's your impeller. Can you post a photo of it?
HBjetHB why do you say that? I would think that when you are taking off out of the hole with turbulent water and air to start with the lip may exacerbate the situation. When you are on a plane I would think that the lip would reduce performance because of the drag but you would still have enough flow to keep the impeller loaded.
As I said before I am not an expert I am just theorizing here.

[HBjet]

miller19j:
HB why do you say that? I would think that when you are taking off out of the hole with turbulent water and air to start with the lip may exacerbate the situation. When you are on a plane I would think that the lip would reduce performance because of the drag but you would still have enough flow to keep the impeller loaded.
As I said before I am not an expert I am just theorizing here.When your idling around, I find it hard to believe there would be air in the pump. When getting on plane the rate of water entering the pump and over that 7/16" step in the shoe is far less then when your at speed where there currently isn't any cavatation. When your at speed, you have top loader grates and such to help keep the pump loaded, but when getting on plane, it's not that crucial. Therefore, that little 7/16" step is not causing the cavitation when getting on plane. What do you think the outcome would be with a pump that didn't have a machined shoe, and was using a rock grate with the same impeller and same power? What about with a ski loader grate? I think the outcome would be the same if the impeller was the same. When Wes conductes his second test after using a detailed impeller, I think he will see that his problem was fixed.
But hey, what the hell do I know!
[ August 07, 2002, 12:01 PM: Message edited by: HBjet ]

[miller19j]

Well when he does his test we will know one way or another. Either way it is good reference material for the future. I have some plans for my jet this winter and the more information that I can gather from other peoples experiences the better as far as I am concerned.

[Slick]

Wes,
I would guess it's that Aluminum impellar that's causing your problem, too much hp for it. All that trick shit on your boat and a stock AA? That surprises me.
Aren't you getting a stainless impellar from Aggressor? You're running around 600hp, right? If so, you're kind of borderline between AA and A. If Dave sends you a SS "AA", run it. If you don't see the RPMs you like, have MPD or Ultra's jet guy cut it down a bit. I bet you'll see a significant difference right out of the box.

[miller19j]

Why is a stainless impeller better besides the stronger material? Is it machined differently held to tighter tolerance’s ?

[Slick]

Stainless or bronze will not flex as easily as aluminum. It carries the same principles as an aluminum prop on an outdrive. Big hp means you can throw the aluminum jobby in the trash and spend big $$ on a SS prop.

[Jordy]

Slick, now in case any eco-terrorists are hanging out here, we dont throw our aluminum jobbys in the trash, we recycle to save the planet.
Jordy :D
Man, I almost said that with a straight face. Ha ha ha

[Liberator TJ1984]

HBjet , would running a backcut shoe on my 19' Liberator make that much of a difference at top speed or launch? I can easily blow the pump out at launch if i nail it hard..but on the big end it stays hooked up really good !!! :confused:

[cyclone]

Ok I have a question. My pump stays completely loaded out of the hole even if I put the pedal to the floor from idle. Its a monster out the hole but comes unloaded in chop pretty easily. The intake is all stock. Is there something I buy to keep the pump loaded in chop and possibly get a small amount of lift?

[RiverDave2]

Froggystyle:
Thanks Dave, but unfortunately, the shoe is not quite square with the pump either, so it will not look square with the bolt holes. This is the result of actually scribing the intake hole with it in place. As you can see, it matches perfectly with the intake. It is unfortunate, and shows a lack of either quality control on Berkeley's part (CP performance) or Hardin Marine (CP Performance) who made the shoe and ride plate.
What I would like to do is build a new ride plate, as mine has a swallow tail on it that noone who knows what they're doing can figure out why. I want to build another plate with a square edge. I probably need a drill press and countersink bit for that....Bring the old plate by this weekend and I'll make ya one of those while I'm at it. Should take less then an hour to make one.. You gotta polish it yourself though.
RD

[RiverDave2]

Licketty Split:
The draw back of sand casting.. Mine is sloght ly off too
Great post thxFrom the picture that intake thingy doesn't look like any sand casting that I've ever seen.
RD

[RiverDave2]

Froggy, I've been thinking about this a lot, and that little step from your shoe to your intake shouldn't be causing you to cavitate. What impeller do you have and what condition is it in? can you post a photo of it? Thanks
HBjet HBJet, why is it that they don't make step bottom jets? I would think A little step directly in front of the intake stream of a jet could most certainly cause Wes's symptoms.
As far as the pump not cavitating on the big end, I believe that it might have a little to do with his setup. I think he mentioned somewhere that he had (I think you jetboat guys call it) some shoe below the boat. Think about it this way..
If that step were disturbing or displacing any water, while the boat is getting onto plane it's bow up before it rolls over. That step could in effect be displacing water over the outside of the intake creating an air pocket. When the boat lays flat again it's still creating an air pocket but the "shoe" or whatever is catching water and shoving it in there as well. I dunno I'm just hypothesizing becuase I dunno shit about jets.. I can tell you though that if you have flowing water then some sort of sharp edge or step it will create a "disturbance." Whether that be an aeration effect, or a big air pocket either one would cause a jet to "cavitate" (even though that's not the right word to use)..
P.S. Cavitate is a prop term.. wink I don't think it applies here nearly as well as just saying I'm sucking air into the intake instead of water.
RD
[ August 07, 2002, 01:46 PM: Message edited by: RiverDave2 ]

[HBjet]

Liberator TJ1984:
HBjet , would running a backcut shoe on my 19' Liberator make that much of a difference at top speed or launch? I can easily blow the pump out at launch if i nail it hard..but on the big end it stays hooked up really good !!! :confused: A back cut shoe will give you more lift when your at WOT, therefore more boat being out of the water = more speed. I would install a cavitation reducer to help from blowing the pump when getting on plane at WOT.
HBjet

[HBjet]

RiverDave2:
HBJet, why is it that they don't make step bottom jets? I would think A little step directly in front of the intake stream of a jet could most certainly cause Wes's symptoms.
RDAt step on the bottom of the hull verses a 7/16" step inside the intake are totally different.
HBjet

[HBjet]

RiverDave2:
If that step were disturbing or displacing any water, while the boat is getting onto plane it's bow up before it rolls over. That step could in effect be displacing water over the outside of the intake creating an air pocket. When the boat lays flat again it's still creating an air pocket but the "shoe" or whatever is catching water and shoving it in there as well. I dunno I'm just hypothesizing becuase I dunno shit about jets.. I can tell you though that if you have flowing water then some sort of sharp edge or step it will create a "disturbance." Whether that be an aeration effect, or a big air pocket either one would cause a jet to "cavitate" (even though that's not the right word to use)...RD RiverDave2:
I dunno I'm just hypothesizing becuase I dunno shit about jets..You got that right!

[RiverDave2]

HBJet, it would seem to me that a "step" or any disturbance INSIDE the intake would make a HUGE difference in the performance of the pump.
Disturbances can create air pockets and air bubbles.. Either one of those would cause what you call "cavitation." Becuase the boat is on plane and has a whatever the **** ya call it hanging down off the bottom it is helping to load the jet on the top end. I would still bet though that air is being crammed in there with the water.
If he can figure out his "cavitation" (god I struggle using that word with a jet) on the low end I would be willing to bet that he picks up some GPM in the pump flow rate as well resulting in a higher top end as well.
RD

[Hustler]

RD what is your definition of cavition ? just wondering since you seem to that a pump cant cavitate.

[miller19j]

RiverDave2:
[QUOTE]
P.S. Cavitate is a prop term.. wink I don't think it applies here nearly as well as just saying I'm sucking air into the intake instead of water.
RDRD I hate to sound like a smart ass but since I used the term I thought that I should justify it. Cavitation is not a prop term it is a Hydrodynamic Term.
Cavitation = The formation of partial vacuums in a liquid body by swiftly moving a solid body through the liquid body.
[ August 07, 2002, 02:09 PM: Message edited by: miller19j ]

[Liberator TJ1984]

Thanks HB..so thats finally what a prop is good for !!! keeping your impeller loaded..I'll check into that...but won't it knock off speed on the big end ? :D

[HBjet]

Ok River"Prop In The Front"Dave. Care to have a little friendly bet? I say Wes will notice little or no difference with the current shoe mod he has performed verses running a detailed impeller verses the stock one he has.
Also, once Wes installs the detailed impeller, I would like to test it with an identical shoe as his original one and see what the results are.
What do you say Wes? Can do this? I'll get the shoe and come one down and install it for ya bud!
HBjet

[HBjet]

Liberator TJ1984:
Thanks HB..so thats finally what a prop is good for !!! keeping your impeller loaded..I'll check into that...but won't it knock off speed on the big end ? :D No, you will only notice it when getting on plane. After that you won't notice a loss, or gain on the big end. If you plan on getting one, I highly recommend getting a detailed one from MPD (because I don't know of anyone else detailing them) A stock Cavitation Reducer actully will induce cavitation. I'll see if I can get some photos of the two side by side. You will see what I'm talking about.
HBjet

[Liberator TJ1984]

HB , One more thing on backcutting the shoe ..do you do that and if so how much...or do I buy a completely new shoe?

[RiverDave2]

RD I hate to sound like a smart ass but since I used the term I thought that I should justify it. Cavitation is not a prop term it is a Hydrodynamic Term.
Cavitation = The formation of partial vacuums in a liquid body by swiftly moving a solid body through the liquid bodyI think your definition of Cavitation is Wrong.. It has more to do with low pressure regions and water "flash boiling" then it has to do with moving anything "swiftly."
Cavitation =
Formation of vapor bubbles within a liquid at low-pressure regions that occur in places where the liquid has been accelerated to high velocities, as in the operation of centrifugal pumps, water turbines, and marine propellers. Cavitation is undesirable because it produces extensive erosion of the rotating blades, additional noise from the resultant knocking and vibrations, and a significant reduction of efficiency because it distorts the flow pattern. The cavities form when the pressure of the liquid has been reduced to its vapor pressure; they expand as the pressure is further reduced along with the flow, and they suddenly collapse when they reach regions of higher pressure.
Yes it is possible to have cavitation in "pumps" but (once again this is me not knowing shit about jets) isn't there POSSITIVE pressure in the intake of jets?
doesn't seem like there's any vacuum being pulled at all. Let alone enough vacuum to cause the phenomenon known as CAVITATION.
I dunno you tell me.. (not trying to be a smart ass either)
What you guys are talking about is "aeration" where a disturbance upstream of the intake is actually creating a disturbance and possibly creating a pocket of air, or perhaps 1000's of airbubbles causing the pump to act like it's "cavitating."
RD
[ August 07, 2002, 02:47 PM: Message edited by: RiverDave2 ]

[RiverDave2]

He steps back, He shoots!!!
Swish.... 3 points and the crowd goes wild... ((((((AAAAAHHHHHHH)))))))
Ok now I'm being a smart ass... LOL
I'm just jokin with ya bud. I figured I'd lighten things up a little bit with some humor.
RD <----- "Where's my Shoe Deal?"
[ August 07, 2002, 02:51 PM: Message edited by: RiverDave2 ]

[miller19j]

RD you crack me up. My definition is from Webster’s Dictionary it is not my own. I admit that it is a very simplified definition but my point was that it had nothing to do with a prop.
I agree with you that there is positive pressure in jets when they are on a plane but when you are getting on a plane there is probably negative pressure especially if you are cavitating (RD you can insert your own word here if it makes you more comfortable).
As far as your definition goes you must have paid for the good version of the dictionary because it is much more in depth than mine!
Don’t worry about me getting defensive I come here for information. I am not an expert that is why I am here.
Miller19j

[HBjet]

Liberator TJ1984:
HB , One more thing on backcutting the shoe ..do you do that and if so how much...or do I buy a completely new shoe?I don't do that, and you would need a completely new shoe made. Contact MPD. They are making them. As for the cost, I think there around 150-160 bucks. Your not local but I'm sure they can still get you the right one, but they prefer to have the boat there and measure everything out. Call them and see what they can do for you.
MPD (http://home.pacbell.net/jmcclure/)
HBjet

[RiverDave2]

Ya know I don't know enough about jets to know if there pullin vacuum gettin on plane or not. I would think that it you were to put a gauge in the intake it wouldn't go below zero, but who knows?
Any of you jet guys have a vacuum/boost gauge on your intakes?
RD

[MikeF]

FS, It seems that your pump is very efficient. Question is where is the cavitation coming from. Maybe the impeller and inducer can't supply enough water into the intake (@ slow hull speed...not enough water to flow into the intake). Possibly the water is being sucked in so hard as to "find" it's way around the skegs on the intake. This suction could cause the separation of the water to the outside of the skegs leading to the induction of air.
The skegs are cut down on my intake (circle/ex record holding Liberty). Mike

[jweeks123]

RD, you might be asking the wrong guys here. If you look at the jets at the races, most have some sort of pressure measuring device on the intake. some have data collection systems and those guys will tell you that the intake pressure varies both positive and negative depending on the situation.
jw

[HBjet]

cyclone:
Ok I have a question. My pump stays completely loaded out of the hole even if I put the pedal to the floor from idle. Its a monster out the hole but comes unloaded in chop pretty easily. The intake is all stock. Is there something I buy to keep the pump loaded in chop and possibly get a small amount of lift?I was having the same problem. I'm going to be trying out a different intake grate this weekend at CBBB and I'll let you know how it runs. I used to run the ski grate and it just seems to not keep the pump loaded when your in a little chop. As for lift, a cut back shoe will get you some more.
HBjet

[Slick]

riodog:
Gee Kids, are we having jetboat fun yet? I aren't either,(expert,that is) but here's some food for thought.#1. Cavitation is basically the pump sucking air along with the water instead of 100% water, therefore 'where is the air coming from"? I've been told that a jet pump can draw air from the transom to the intake if you mash the throtle from a dead stop.
For many reasons besides this, I wish my POS was in the water. I've got a brand new DPS cavitation reducer in my pump along with the detailed SS "A" impellar. That way I could say how great the cavitation reducer is.
I still say it's the impellar. But then again, his boat runs and mine doesn't.

[HBjet]

Slick:
I still say it's the impellar. But then again, his boat runs and mine doesn't.At least yours doesn't cavitate!
HBjet

[ChetCapoli]

HBjet:
Hey Chet, so how did the boat run, a lot of us are waiting to here if all that bottom work paid off. Weren't you at 80mph before the work, what did it do now? Thanks
HBjetI'll keep ya posted HB, dont you worry. :) The ride is a world of difference from before i can tell you that. No numbers worth mentioning as of yet though. BTW, The water conditions this weekend weren't the best, lots of traffic, and a few bugs(and blunders on my part)that i had to work thru.
CHET
[ August 07, 2002, 08:40 PM: Message edited by: ChetCapoli ]

[ChetCapoli]

[QUOTE]Originally posted by HBjet:
I have seen a new Berkeley Aluminum impeller and it didn't look too good (Even an Aggressor Aluminum looked better) I even told the owner of Berkeley when I met him that his Aluminum impellers weren't perfect. He said he knows.
That still makes me laugh hb...wasnt the correct term "junk" though?? I just cant imagine the owner of berkeley saying something along the lines of "if you want to run fast with my impeller, you basically have to reconstruct it" every time he sells an impeller. Do me a favor if you get time ok? Put a pic of a stock berk, stock aggr, stock legend and one of your favorite "magically detailed" impellers on here for us viewers(in that order if you would please....junk------>state of the art). One more request while i'm at it. When you take the shots of the DPS inducer, stock and detailed, take a shot of the precision jetdrive "billet" inducer also and tell me what you think.
you the man
CHET
P.S. even an aggressor aluminum looked better! LMAO!

[HBjet]

Cyclone, here is a photo of the loader grate I've been using (Right) and the one I'm going to try out this weekend (Left) If I like it, I'll have one made, if I don't, I'll try another. Are you using the same grate as the one on the Right?
http://home.socal.rr.com/boatbutts/grates.jpg
HBjet

[HBjet]

Ok, let's talk about cavitation!
RiverDave, Wes, whoever. Will the little steps that I've found in my pump cause cavitation? I've pointed them out for you with arrows.
http://home.socal.rr.com/boatbutts/cavitation.jpg
Now, RiverDave, since that little 7/16" step on Froggy's shoe causes millions of air bubbles to form, therefore causing cavitation. What about this space on the top of my pump where the hand hole cover is? Wouldn't this also produce millions of air bubbles, causing cavitation?
http://home.socal.rr.com/boatbutts/cavitation2.jpg
Thanks for you help!
HBjet
[ August 08, 2002, 12:25 AM: Message edited by: HBjet ]

[HBjet]

Now Chet, do you know of any out of the box aluminum impeller that looks this clean?
http://home.socal.rr.com/boatbutts/legend.jpg
BTW, this impeller was worked on over 2 years ago.
HBjet

[canuck1]

RD[/QUOTE]
HBJet, why is it that they don't make step bottom jets?
RD they do make step tech hulls
[ August 08, 2002, 01:14 AM: Message edited by: canuck1 ]

[Froggystyle]

I'm not sure who posted what, so I will get to the answers as soon as I remember them...
Intake gauge. I have one. When I give it the spurs from idle it registers close to zero pounds. It is probably in a vacuum state at that point and sucking water in. Maybe not. At full speed, that gauge reads between 15-25 depending on impeller. I am hoping for 35 someday.
Detailed impeller. I just took one out. I have now run 3 different impellers in this boat. The worst performance was with a stock Berkeley "A" and it had real problems. Rick from CP then sent me a "detailed" A that looked like shit still, along with a billet stuffer and three different loader types. Chris Wheeler from Ultra Performance massaged the already detailed "A" impeller and I have been running that since August of last year. After talking with Rick from CP again this year at the LA Boat show, he and I concluded that an A2 might solve the problem, though I really wanted to step down a size, not up. My motor makes all of it's power at 5800 rpms, and I was currently only turning 5600. But, to improve my holeshot, I was willing to try the larger impeller. Plus, the price was right. I received the impeller in June, and was going to have it detailed but decided to run it and see first, as detailing the first "A" did nothing perceiveable. I gained no holeshot, no top speed etc...
I do have pictures of all of the impellers, and will post them later to show everyone the differences between a stock Berkeley and a detailed, an "A" cut vs an "A2" and how Agressor's impeller fits into the mix.
Bowls... I have an American Turbine racing bowl that Ron Gordon sent me to try out. It is not drilled for my ride plate though, so when I am ready to give it a whirl, and think I have solved my cavitation problems I will bolt it on and give him the best shot at seeing an improvement too.
Cavitation. Whether it is the right word for the occurrence or not, it is the industries definition, not mine. The fact is that a harsh lip impinging on a column of water is going to create a low pressure spot behind it, and in this spot water vapor (air/steam/whatever) will be created. When this vapor bubble(s) is sucked into the impeller, and is treated to some high pressure it will be crushed and create cavitation at the impeller face. This will be a self-fulfilling prophecy at this point, because a cavitating impeller will never load again without removing the power and re-loading it. On that note, the one problem I don't have is unloading at speed. Zero problems with the pump blowing out in rough chop or the like. Once I have rolled the boat over, it hooks up hard.
RiverDave stumbled on the best point yet, and that has to do with the amount of bowrise I get while trying to get on plane. This 7/16" step is not actually 7/16" at all when flattenned like if you were on plane. It is kindof a rolling lip. If stood up though, it becomes a noticeable step, and could certainly be involved in a cavitation scenario.
Lastly, I didn't say this was going to solve it. I do plan on trying a cavitation inducer, as I always have. I also plan on running an AB cut impeller. I want to solve whatever problem is causing this first though, and just reap the increased performance benefits of the inducer once it is solved. I am also hoping that the inducer in conjunction with the AB will still be stiff enough for this motor.
Squirts up.

[HBjet]

Thanks for the post, and thanks for doing these tests.
HBjet

[pops1]

Froggystyle
Squirts up.[/QB]Frog your going at it right!Solve your intake load problem. If then- and I say "If" you need a Inducer put it in after all is complete. Take a position on your berkeley as a base unit. "Run that unit as is" including bowl.
Max your MPH on that set-up- Then and only then start changing 1 Item at a time. This way you have your base to test against.
Tom is still going on his base on the Coach unit- Bottom changes, motor changes, always being tested to the base.
After all this is done and you feel comfortable about it- Try your change (1) at a time.
A good flowing Bowl can increase you by 60cfm - this can lower your intake pressure/Bowl pressure and so on, causing your boat to run deeper in the water(increasing your wetted surface "drag").
Your speed drops and first indication is "No Workie" Yet the real fact is- it works after corrections or adjustments are made. Bingo 3 MPH
two tenths quicker.
If you go back to a Bowl Test done by "real jet boats" Mike & others ran. Read the text and you will see they did not know what they were doing.
The net result was a product that works for most, fell on its head under that test basis.
We have gone thru the same condition on our 11 vane bowl which goes up 48cfm over the 9 vane and now this bowl "back east" is starting to kick some serious numbers.
Good Job-Dave
[ August 09, 2002, 10:53 AM: Message edited by: pops1 ]

[Froggystyle]

Thanks for the post Dave. Any idea why my intake pressure is so low? Seems like unreadably low at takeoff and 15-25 at speed dependent on loader and impeller.
All I know for sure is that the A2 impeller slowed me down huge, and didn't help my cavitation one bit.
Wes

[Froggystyle]

HBjet:
Ok, let's talk about cavitation!
RNow, RiverDave, since that little 7/16" step on Froggy's shoe causes millions of air bubbles to form, therefore causing cavitation. What about this space on the top of my pump where the hand hole cover is? Wouldn't this also produce millions of air bubbles, causing cavitation?
I don't think so. The gaps in your handhold would not disrupt the laminar flow of the water, only create a still part within the gaps that would not flow. If the hand hole cover stuck down below the intake, and had a sharp edge then yes, I would say it would cause problems.
Froggy"makingmethinkaboutbondoingmyhandhole"style

[wsm9808]

On the subject of cavitation, I would like to ad it does not nessaraly mean you are mixing air with your water, that is ariation. In the oil field we have pumps that cavatate in a "closed" inviroment, meaning a solid coloum of water in a pipe from the bottom of a tank being pumped to another station. When run at the wrong speed, they cavatate. Zero air enters the system. If you could hear your pump cavatate over the sound of your engine it sounds like gravel caught in a mixing bowl or in a hubcap rolling down the road. You can hear it easily on a stationay pump driven by an electric motor.
What is actualy happening is the impeller is drawing the water in faster than the incoming water can move and the water is being streched so violently that it seperates the hydrogen from the oxygen and creates a tiny explosion when they pull apart. That is what "burns" your impeller. Pull your finger, that pop you hear is nitogen being released from your joint, not the same thing, but might get you thinking along those lines.
they named it a suction housing because is does run under negative pressure untill you have enough speed to "pack" the intake with more water than the impeller can use, then you build pressure in the intake.
ooops, better get back to work, but their is a lot more to ad to this. Sorry bout the crappy spelling, but I was in a hurry.
The idea pump would have huge eye and intake that could grab tons of water at low intake speed and high horsepower, and then as boat speed increased the intake, impeller eye and discharge nozzels would all reduce in size as speed increased.
I dont agee with HB about much, but I think he on the mark with saying you will see more results from an improved impeller than shoe work, a shoe shouldnt even come into play untill around 60 mph. sounds like your heavy boat and high HP are to much for the impeller and intake volumes.
my .02 :cool:

[jweeks123]

sorry if I'm repeating myself from another thread. I think if you guys are really interested in this stuff you should go to the races and talk to the guys that have data collection systems on their race boats. they seem to know about solutions for cav. have you ever watched how hard they come out of the gate? I see tem sit on the rope til their number comes up and then - boom! gone. ask question in the pits. I know they have data about cav and what to do about it.
you guys don't just go to the races to drink beer and watch some big noisy fueler crash, do ya??
jw

[jweeks123]

maybe I should have suggested that froggy take his boat to the races. the race guys really make improvements. look at Bobp - his very old southwind might run away from frogy's new ride, at least until froggy learn the racers tricks
jw

[canuck1]

Froggy
What size nozzle do you have on now? On the sprint we go to a larger one for holeshot and a smaller one for top end. I'll measure them and give you sizes for comparison

[wsm9808]

race boats and heavey lake boats are apples and oranges, you could pull a hard launching pump out of a 200 pound race hull and bolt it into froggys boat and it would cavitate.
Also I think the blending work he is doing in the intake and shoe area is a good step and will help most in the 25 to 50 mph range or what ever speed the intake is loaded but at low to neutral pressure. I did it to mine last year and could tell a little bit in the mid range. But if it is slipping as bad as he makes it sound, then it will take several changes in combination to be able to feel a notable differance. Kinda Like increasing horse power in the engine, adding one speed part wont make much differance.

[Froggystyle]

My nozzle is a stock Place diverter nozzle. I believe it is as big as they get.
jweeks123... I know I am cavitating because of too much draw, not enough water. The question is, what can I do to get rid of it. I appreciate your analogy and experience with the water pumps though. I think it is a similar creature.
I just pulled out a completely detailed impeller. No perceived difference between it and a stock one of the same size. Same top end, same cavitation, etc... Impeller mods are over. There is no where to go. I am already running a closer-than-most-raceboats tolerance of .015 and have experimented with a detailed impeller vs. stock, billet stuffer or not, and six intake grates. Whether or not the lip has anything to do with it, I expect that by opening up the intake opening 3/4" it should work better. Smoothing out the flow just eliminated one more possible hangup causing my cavitation.
Mike Harlan had about the same horsepower I have , a little less in fact, in a closed bow 22 Stealth. Similar weights, similar bottoms. He ran his with a Pro-Dominator which has the inducer impeller built in and it absolutely shot out of the hole, in fact it posted the very fastest 0-60 time of any tested boat in Hot Boat's history. I can't imagine the inducer did all of that. Mine would rival the slowest tested right now. I can't even pull up a wakeboarder without boiling water. Something is wrong... and it isn't obvious. This same setup leaves hard in other boats. The only difference is that it is a Berkeley, not a Dominator (and I am not comparing it to Pro Dominators either)
I know the inducer is next. But I want to find a little more holeshot before I do.
This pictorial was mostly just to show everyone that there are some easily rectified flaws in the stock gear. A couple well-planned hours and a grinder solves most of them.
Squirts up!
Wes

[Froggystyle]

wsm9808:
race boats and heavey lake boats are apples and oranges, you could pull a hard launching pump out of a 200 pound race hull and bolt it into froggys boat and it would cavitate.
Also I think the blending work he is doing in the intake and shoe area is a good step and will help most in the 25 to 50 mph range or what ever speed the intake is loaded but at low to neutral pressure. I did it to mine last year and could tell a little bit in the mid range. But if it is slipping as bad as he makes it sound, then it will take several changes in combination to be able to feel a notable differance. Kinda Like increasing horse power in the engine, adding one speed part wont make much differance.Got any ideas? I can e-mail you the specs if you want.
I am considering three different possible actions.
A) remount my intake to be a 6 degree intake instead of 4 degrees
B) run an inducer impeller
C) Switch to a V-drive
Just kidding. I would never buy an inducer. hehe

[wsm9808]

Mine was a bad miss-match too. Not just the shoe but the suction to intake was about 1/4" off too. I personaly feel the inducer would give the most seat of the pants differance. It should help get the water moving toward the impeller and not leave it all up to the impeller to draw the water in. Think about what is happening when you gas it from a stand still. The leading edge of the impeller graps a section of stationary water and with tremendus force janks it into the pump. Imagine how fast the water setting in the intake must react and start moving to fill the void by 4 vanes snatching up slices of water at 5000 rpm.

[comin' unscrewed]

Froggystyle:
[QUOTE]
C) Switch to a V-drive
NO FROGGY!! Doan do eet!!!

[burbanite]

Good thread, I'm learning a lot.
Hopefully there will be a lot more that comes out of this and I think the comment about asking info of the racers is valid (differences in use not withstandind). Just look at the V-drive section, they are all over a question from a non racer, some things do translate - it's just physics after all.

[Kwicherbichen]

Wes, I know this challenge is troubling you and I'm sure you will get it figured out one way or another. At this point I would make a series of calls to some of the guys up our way. Their knowledge is indispensible.
You can call Tom Papp (909-734-4606) Mon-Sat from around 7am-6pm and I'm sure he would gladly give you his opinion. In fact you could just tow the rig up there and let him look at it. That way you could at least bat some other ideas around. I recommend Tom because I know him personally and I've seen him work but, you could also hit up Greg and Jack just to round out the opinion trek. I'm sure you've already asked some pretty knowledgable folks and I'll bet a few more couldn't hurt?
That's all I can really offer to your dilema because I don't know shit about this stuff but, I did stay in a Holiday Inn last night....LOL
[ August 10, 2002, 12:59 AM: Message edited by: Kwicherbichen ]

[bp]

froggy, i believe you headed in the right direction by enlarging your opening. as far as the lip? well, it's always nice to smooth things out, but that has nothing to do with your holeshot cavitation. it's too bad you couldn't smooth things, test, then enlarge the opening and test. this is the same reason they're trying to develop dual drives - more volume.
for a heavier boat, expecially with higher hp, the most effective way to improve your holeshot is the cavitation reducer. curly will tell you that, and jack would tell you that. i've had one in the southwind for 3 years, and it does make a difference.
the suction piece does go negative (less than atmospheric) at the hit, in my case for a very short period. i have a mountain of data i could show you to support that. the good thing is that discharge (bowl) pressure continues to climb as speed picks up and suction pressure recovers. this is all within the first second of a run. if i see discharge pressure start to falter at that point, i will adjust my engine acceleration rate via the launch controller (rev limit/time delay).
just keep in mind that everything you do to affect performance at one point in your run will have an affect on performance at the other end.
good luck; maybe we'll see ya at the races sometime!

[Froggystyle]

When are the next races? I'm thinking it would be fun to take out some batteries, pull out the anchor and go race this pig. Just for fun of course.
Wes

[wsm9808]

bp brings up an other good point about modern race boats, with electronic controls they can control the rate the rpm climbs out of the hole and not have acceleration overun that makes the impeller loose grip out of the hole. If I'm not misstaken, I believe that up untill somewhere in the 1980's the drag boat racers actually came up to the starting lights at a low speed side by side and nailed it as they approched when the starter hit the green.. I'm sure at some point you have gotten your boat up to 3 or 4 mph and then hit it and had very little or no caviatation and the boat accelerates hard. Hull presure packs more water pressure into the suction than the impeller needs at that speed, and then when you nail it the water is "primed" to flow and the pressure drop in the intake is not as dramatic.
If anyone is interested Jac Sea wrote a jet tech article titled Super Jet Buildup in the march/April 1987 ***boat. (If anyone has the May/June 1987 I would like to buy it) Here is a section from that
"Under acceleration, the suction piece does what its name implies. There is low pressure in the inlet area and your impeller must suck(its a pump remember) an adequate supply of water so it can pressurize the bowl. An inadequate supply of water will be a prime contributor to acceleration cavitation. Aceleration cavitation is the phenomenon where you nail it and the rpm go to 5200 then drop back to 4800 as you accelerate. If you drop hammer at very low speed and have acceleration overrun(mometary)of much more than 200 rpm you'll have either, or a combination of these things:
(A) inlet hardware which will not tolerate low speed full throttle acceleration
(B) loose wear ring to impeller fit
(C) damaged leading edges on the impeller blades
A good Jacu12W has NO RPM overun(large inlet) "
It is an excellent article packed with imformation about pump design and function. Maybe if we bugged them enough Hot Boat would put together a pamplet with all of Jac Seas articles. He didnt just give a blow off answer in his replies to tech, he would explain why that was the answer too.
A huge problem that is killing/has killed the jet boat industry is that there is no "HOW TO HOT ROD YOU JET PUMP" book out there. there is no central sorse of performance information to build from. Anyone that wants to hop up their jet or race has to start from scratch with the basics and dig and begg for information and use trial and error based on speculation. Each new generation of jetters have to re-learn everything to get to where the old timers have already been, insted of being able to experiment with new ideas and make performance advances.
For example, look at the pics HB posted of his impeller. From the wear pattern of paint on the leading edge of the blade one could assume that the water lifts away from the blade as it bites into the water. Because the paint is not worn off the leading edge, there must be nothing touching it to wear it off, Right? Sooooo, with the water naturaly flowing in that pattern, wouldnt an air foil shaped leading edge that was contured in the shape of the water flow be less disruptive to the flow and take a cleaner smoother bite on the incoming water and thus cause less turbulance and create smoother quicker acceleration rate of water into the intake? Less cavitation? I dont know, but how would you know if anyone has tested it?
[ August 10, 2002, 11:21 PM: Message edited by: wsm9808 ]

[wsm9808]

As far as increasing the opening, It might help a little, but dont forget your pump is a designed compromise. At high speeds (over 60) an inlet no larger than the eye of the impeller is sufficient, and a super large intake will have too much pressure build up. The extra pressure cannot be forced through the impeller, so excess water will have to flow off the back edges of the inlet opening causing intake turbulance with water intering, swirling around and exiting.
To increase intake volume you could take out the intake loader(it takes up space) to simulate a larger intake volume and see if it helps the hole shot. In deep water of course.

[MikeC]

If all else fails, READ the MANUAL!
This is great stuff from Jack S.
(A) inlet hardware which will not tolerate low speed full throttle acceleration
(B) loose wear ring to impeller fit
(C) damaged leading edges on the impeller blades
Great to have some info from a real Pro every now and then!
I think he could add one more for today's Jet Boaters,
(D) A impeller that has been shaped by a prop guy or such...
Froggy, I'd play around with differant loaders. Just my opinion as to what effects my holeshot the most.
Anxios to here how things went,
MikeC
PS: Aggressor, it was MikeW from http://nothinbutjets.com that did the tests with the bowls, not me. I don't have the $ to play around with all this stuff so I only run what the Jet Racers run at the track... :-)

[Moomawnster]

"the water is being streched so violently that it seperates the hydrogen from the oxygen and creates a tiny explosion when they pull apart." Thanks wsm9808! I have been waiting to see if anybody else knew the physics of cavitation ....the most important part of it is that outside air need not be involved... :rolleyes: :D

[jweeks123]

I don't agree about the H2 separating from the O. The water simply turns to vapor (boils) in local areas. see the following reference:
http://www.rampump.com/handbook/cavitate.html
jw

[Froggystyle]

Regardless of the physical definition... the bad news is, define it how you want, the boat still does it.
Not as bad, but nowhere near acceptable. I am now out of ideas short of the loader impeller. I have run the gamut of loaders, grates, impellers, detailed impellers, larger impellers, massaged intake shoes, billet stuffers and decreased tolerances and nothing has made any recognizeable difference, and the only catagorical difference so far is that the addition of the "A2" impeller took my max RPM's from 5600 to 5100 or so. Top speed today was only 72 mph as well.
Intake pressures. I am negative until around 35 mph. This week I will be buying a vacuum/pressure gauge to better define what it is going down to, but the very highest it gets, at 72 is around 20 lbs. It would appear obvious to a casual observer that I am not getting enough water into the jet for some reason, and need to figure out a solution. Does anyone have any ideas short of the loader impeller? That is obvious, but I am interested in other ideas.
Thanks ahead of time.
Wes

[HBjet]

Froggystyle:
Intake pressures. I am negative until around 35 mph..........It would appear obvious to a casual observer that I am not getting enough water into the jet for some reason, and need to figure out a solution. Does anyone have any ideas short of the loader impeller? That is obvious, but I am interested in other ideas.
Thanks ahead of time.
WesWes, the next step I would take short of installing the cavitation reducer is playing with nozzle inserts. You have the stock PD nozzle, you have no way to get enough water in the jet, and you have ZERO intake pressure. So if you reduce the nozzle size of the water exiting, you would be creating back pressure, therefore keeping the pump loaded. That might just do the trick for you.
Let me know what you think.
HBjet

[Froggystyle]

Ya know... that is not a bad idea. But I would have to get my pump machined. If only I knew someone with a machine shop..... :D
Any response to this? Seems in theory correct, but I don't think it would add any backpressure to speak of, since there is no water going out either when it cavitates. I am convinced it is an intake issue, or approach to the intake.
Personally, I think the next step is to re-mount the intake at 6 degrees and see what happens. My problems appear to have everything to do with attitude of the boat, as when it rolls over is when I start to come out of the negative pressure into the positive.

[miller19j]

Wes,
I have a small machine shop and would be happy to make an insert for you if you can’t find someone else to do it
Miller19j

[pops1]

Froggystyle:
Thanks for the post Dave. Any idea why my intake pressure is so low? Seems like unreadably low at takeoff and 15-25 at speed dependent on loader and impeller.
All I know for sure is that the A2 impeller slowed me down huge, and didn't help my cavitation one bit.
WesWes.I thought your intake opening was way under size. Under 13" or something. Have you opened it up yet. If your undersize on the mouth opening all you will get is cavatation-due to lack of water. Thats why i say don't put a cavatation reducer in untill you overcome your lack of water problem. Don't get pushed into a state of confusion. Stay to the basics, 1 change at a time. Your overshoe'd below the keel because your undersize on mouth opening. I thought you were going to pull the intake out open it & reset the intake.
Everything will change and your spinning your wheels untill you get this corrected.- It was was 1" under as I recall in our conversation.. Dave
[ August 12, 2002, 10:21 AM: Message edited by: pops1 ]

[Froggystyle]

Pops,
I changed the opening as large as the stock intake would allow. It opened from a 13.25" hole measured at the back part of the half circle created by the shoe to 14.00" even. It made a small difference, but nothing close to what I need to do.
Do you think running a smaller impeller, one that is not pulling as much water as hard would help the loading problem?

[wsm9808]

jweeks123:
I don't agree about the H2 separating from the O. The water simply turns to vapor (boils) in local areas. see the following reference:
http://www.rampump.com/handbook/cavitate.html
jwI could be wrong, and it wouldn't be the first time; but I didnt see at that link where it said that the water boiled. I read "they rapidly collpse....or implosion". I've never heard boiling water discribed quite like that before, But then, I never heard the term "my bad", till I started coming to these boards.
The seperation thing is what they taught us in a short hydrodynamics class that my old pump shop boss required us to take at the local CC for employment. If its wrong let me know, I'd love to call my old boss and the school and tell them they are a bunch of dumbasses. :D

[pops1]

Froggystyle:
Pops,
I changed the opening as large as the stock intake would allow. It opened from a 13.25" hole measured at the back part of the half circle created by the shoe to 14.00" even. It made a small difference, but nothing close to what I need to do.
Do you think running a smaller impeller, one that is not pulling as much water as hard would help the loading problem?You need to get JP into this- or someone- Your shoe set up is wrong, you are driving a negative position shovel.
Your starting to adjust to something other than a good set-up as your base-now impeller cuts can and will be off to any good baseline standard. Your motor to me says on a good base should be our "B" cut or anyone else's "A" cut. Maybe even a A/B for overall application. Do not settle for less at this point.
You have intake position problems-the way it was set up @ factory, unless you have a Delta Flat down there, which then I might agree (somewhat) on the amount of shoe you have below the Keel line. I think your shoe should be 1/4" or better up inside on a good setup.
"ITS NOT RIGHT" Call Ron again or get Joe to set it up right. What you have is wrong. Go 80 MPH and your in a danger zone. Dave
[ August 12, 2002, 03:00 PM: Message edited by: pops1 ]

[Froggystyle]

Dave, when I let off the throttle at top speed I don't have any handling quirks at all. It just slows down predictably. Is that what you are talking about with "Danger Zone"? Nothing on this boat leads me to concern about safety. It is very predictable, and the only discernable difference between 60 and 78 is a different GPS reading. And more bugs...
What I don't like is that when the diverter is actuated my steering is affected slightly, and it will weave right when diverted down for control. Not much, but a little. I can't see any reason for it, but there it is.
Tomorrow I am going to take the boat out again, and see what the pressure goes to when I let off the throttle from top speed. It should spike up if it is protruding too far, right?
Let me know.

[Froggystyle]

Just thought of something else... I am going to try to relocate some of my weight up front to help it roll over. This should help a little, right?
[ August 13, 2002, 09:08 AM: Message edited by: Froggystyle ]

[pops1]

right?[/QB]Watch for UPS- your Impeller and Inducer are on board. Run it and lets see RPM's- Our "B" should hit you like a Berk "A" If you don't pre-load now "WOW" Hook-UP a 2" Tube to the Intake, You and Co-Pilot slam down 6 beers wait 5 min's, Leak into the Tube untill she loads and you go sound intake pressure.
Its said by good beer drinkers this one always works! Dave
P.S. Don't pull any fine ladies on this run.

[Blown 472]

Maybe you have to adjust your driving style??? I had a single 4bbl on my boat last year and could slam the throttle coming out of a no wake and the boat would break over and haul ass, now that I have a blower on it no dice, cavitates and shakes the hell out of the boat, but if I get it moving and then slam it, it hooks up and goes. I was explained to me that the boat is not moving fast enough to force water into the intake and it is getting sucked dry. :rolleyes:

[pops1]

Blown 472:
Maybe you have to adjust your driving style??? I had a single 4bbl on my boat last year and could slam the throttle coming out of a no wake and the boat would break over and haul ass, now that I have a blower on it no dice, cavitates and shakes the hell out of the boat, but if I get it moving and then slam it, it hooks up and goes. I was explained to me that the boat is not moving fast enough to force water into the intake and it is getting sucked dry. :rolleyes: You may try to get more aggressive on your load- You can load and go
You bumped your HP -did your R's change- if so are you still in the range top end. You should not be to my thinking! 4- bbl to blower- should be a bunch! Dave

[jweeks123]

Huh?

[Blown 472]

Yeah, what are you talking about?? you have lost me. :confused: :confused: :confused:

[NorCal Gameshow]

does the droop have any effect on this ? is it possible to have too close of tolerance(.015)?

[Froggystyle]

Blown 472:
Yeah, what are you talking about?? you have lost me. :confused: :confused: :confused: I think what he was getting at was that if you gained a ton of power, but did not re-set up your pump to make use of that power or load it properly, then you should consider changing the impeller or adding a different loader/grate/preloader impeller.
That was my read on it anyway...
I was using a bone-stock Berk with too much power. I have since needed to do a lot of work to adapt this pump to the boat and motor combination.
As for driving style, I can't even pull a skiier up without cavitating horribly. I have never had this problem on a jet, and can only assume it is that I have a very heavy jet, and the HP is overcoming the impeller's ability to pull water.

[78Eliminator]

Froggystyle:
I can't even pull a skiier up without cavitating horribly. I have never had this problem on a jet, and can only assume it is that I have a very heavy jet, and the HP is overcoming the impeller's ability to pull water.Wes, next time we need to get some skiing time in. Just don't rip my arms out of socket.
J

[Blown 472]

I've got a heavy boat too, 76 glastron. Course I dont have the batteries you are have, did you say you can keep up 140 dp wif your stereo? eek!

[Froggystyle]

Blown 472:
I've got a heavy boat too, 76 glastron. Course I dont have the batteries you are have, did you say you can keep up 140 dp wif your stereo? eek! Yeah. It will play that loud until you get a headache...
I took all of the batteries except one out yesterday morning, plus the toolbox, hardly any gas, no gear and two seats removed. It rolled over a lot faster, which would equate to ET, but the cavitation was still there, and a heavy foot would throw it into convulsions.
Here is the weird part... After removing 1090 lbs of gear, gas and people, and running on a cool day in San Diego with the same GPS... I slowed down .5 mph on the top end from the run at the river with all of the weight on the boat.
I don't get it. I would have thought that 1000 lbs of gear and gas would have made a huge difference, like 5-6 mph faster. It did roll over faster like I said, but I couldn't believe the top speed was so close.
The pump is coming out today to get a cavitation inducer impeller and an Aggressor "B" mag bronze. Should know by the weekend how it works. I am going to leave the gear out for now, and see how it handles the light load.
Squirts up.
Wes

[rivercrazy]

Maybe all the weight in the transom helps load the pump better???
Maybe at speed the weight of the batts keeps the transom angle better suited to loading the pump?
Maybe part of the cavitation is caused by the nose being in the air at takeoff. Is it posible that the angle of the intake to the water is causing the grate to block water?
Perpexing issues there Wes. I bet when you solve it it will equate to 3-5mph better top end and a missle out of the hole.

[Screaming Pete]

Froggy, Props to you for working so hard on this one.I am no expert on this one but have had a couple of jets. My thoughts are 1) Jim Laird had the faster daddy boat and he ended up running lots of hp and went to a dual impeller set up by someone out in your area. He had 21Lx running right at 75-77mph and had dcb blue print the bottom also, 2) What are those river racer's and short course racers running for pumps the info i seen a couple of years ago led me to belive that thier pumps would idel for your size and hp of a boat?
Just my thoughts not trying to impress anyone and good luck with your endevour
:cool:

[HBjet]

Froggystyle:
I slowed down .5 mph on the top end from the run at the river with all of the weight on the boat.
I don't get it.Because you GPS'd the boat going down river?
HBjet

[Froggystyle]

HBjet:
Froggystyle:
I slowed down .5 mph on the top end from the run at the river with all of the weight on the boat.
I don't get it.Because you GPS'd the boat going down river?
HBjetNo, we GPS'd it in Lake Martinez... but thanks.
My reason for stating that it was at the river was for the 92 degree heat zero humidity factor. It should run faster than the best day at the river on a cool morning in San Diego.
Mystery to me.

[HBjet]

Is everything (motor/pump) exactly the same from when you GPS'd it at the river, to yesterdays run, except the weight/gear?

[cruser]

Did the rpm change?

[Froggystyle]

Yes.
BTW. Dave, I got my impeller and DPS preloader in the mail today...
I have to say, they look really nice and well finished. I have taken one single aspect of this testing seriously and with no preconceptions of worth based on company or reputation. I have proven only that the stock Berkeley stuff will not do the job. I don't see any improvement I can make on the setup short of adding a Meirsh intake.
This new phase of testing for all concerned will be focusing on my new Aggressor "B" impeller in Mag-Bronze and a DPS cavitation reducer, both supplied by Aggressor in lieu of the SS impeller won in the contest. Dave feels that this will do more for the boat as a whole than the SS impeller will, so we did some horse trading.
I will start a new topic as soon as I start removing the engine tomorrow to pull the shaft for machining. It will be called Berkeley Mods Episode two, and will compare visually at least the four impellers I have currently and the differences between a detailed Berk, stock, A vs. A2 and the Aggressor Mag-Bronze.
Squirts Up!
Wes

[Froggystyle]

cruser:
Did the rpm change?No.

[Froggystyle]

HBjet:
Is everything (motor/pump) exactly the same from when you GPS'd it at the river, to yesterdays run, except the weight/gear?Yes

[Slick]

Too bad you actually want to get some use out of your boat, Wes. For shits and giggles, I'd like to first see what the Mag-bronze impellar does alone. Then you could settle a little dispute about the cavitation reducers. DPS says, "Hell, no you don't need to detail that thing. It's great right out of the box.". MPD says they need to be cleaned up. If not, they can actually cause cavitation. I've spoken to both on the phone before purchasing mine.
Ofcourse, as we all know, my sweet pump is still sitting on the garage floor, so I have no reports on how the unmodified DPS reducer impoved performance for me.
Slick

[Mohavekid]

Hey Froggy, I've been following this one for a while now and everybody has all kinds of interesting ideas. I have one more possability for you. The packing gland could be too loose, allowing air to be drawn into the suction piece between the packing gland and the the shaft on hard acceleration. This will cause cavitation and higher RPM's at low speed which then drop to normal once speed is up. Just my .02. Good luck.

[Froggystyle]

Mohavekid:
Hey Froggy, I've been following this one for a while now and everybody has all kinds of interesting ideas. I have one more possability for you. The packing gland could be too loose, allowing air to be drawn into the suction piece between the packing gland and the the shaft on hard acceleration. This will cause cavitation and higher RPM's at low speed which then drop to normal once speed is up. Just my .02. Good luck.Thanks for the advice, that was definitely one of the checks. The gland is dripping about once every 30 seconds or so at idle. The intake to suction piece was another spot it could have leaked, and it is dry to the bone. I also siliconed the handhole cover to ensure that wasn't it. Easy stuff first, right? I was hoping upon hope that that was what it was.... but alas... no difference, and they weren't loose.
Wes

[Froggystyle]

Slick:
Too bad you actually want to get some use out of your boat, Wes. For shits and giggles, I'd like to first see what the Mag-bronze impellar does alone. Then you could settle a little dispute about the cavitation reducers. DPS says, "Hell, no you don't need to detail that thing. It's great right out of the box.". MPD says they need to be cleaned up. If not, they can actually cause cavitation. I've spoken to both on the phone before purchasing mine.
Ofcourse, as we all know, my sweet pump is still sitting on the garage floor, so I have no reports on how the unmodified DPS reducer impoved performance for me.
SlickI inspected that little inducer and I think it looks cherry. I can't imagine doing much to it at all. Unless Jack does some kind of magic to the shape or cup, I don't see where there can be an improvement.
Once the engine is out, and the shaft is cut, it is easy to remove the impeller and DPS unit. If I think there are gains to be made... I will detail both. But in my opinion, the Agg impeller and the DPS both look better than either of my Berk pieces, and the impeller is detailed nicer than my detailed "A" aluminum.

[Mohavekid]

Too bad it's not an easy fix. Looking forward to hearing how a new impeller and DPS works out. If the DPS does not work, can you reuse the shaft after it's been machined for the DPS?

[HBjet]

Wes, who detailed your Berkeley aluminim A impeller for you?
As for the DPS, of you saw them side by side, you will see the difference. Can you do me a favor and take a photo of the DPS (up close) so we can see the condition it is in? Thanks!
Good luck on your next step to correcting the problem.
HBjet

[bp]

Mohavekid:
Too bad it's not an easy fix. Looking forward to hearing how a new impeller and DPS works out. If the DPS does not work, can you reuse the shaft after it's been machined for the DPS?yes. but it will work.

[Froggystyle]

We went ahead and detailed the DPS last night, so I can't take a picture of it. Not to mention I don't have a digital camera.
The engine is coming out today, and I am going to pull the shaft out to get it machined on Monday.
Regarding "can you go back once the shaft is cut". From what I understand, taking the DPS out is kindof like removing a place diverter. Doesn't happen. They work too well.
Wes

[BLEWBAYOU1]

FROGGYSTYLE,
THIS MAY SOUND STUPID, BUT WHERE YOU GOING THE SAME DIRECTION ON THE RIVER WHEN YOU DID YOU SPEED COMPARISONS? ITS KIND OF LIKE LAND SPEED VERSUS AIR SPEED OR IN THIS CASE LAND SPEED VERSUS WATER SPEED OF THE RIVER.JUST A THOUGHT. BRIAN

[skeepwerkzaz]

Why was he yelling? Sound like you are working hard.

[Froggystyle]

BLEWBAYOU1:
FROGGYSTYLE,
THIS MAY SOUND STUPID, BUT WHERE YOU GOING THE SAME DIRECTION ON THE RIVER WHEN YOU DID YOU SPEED COMPARISONS? ITS KIND OF LIKE LAND SPEED VERSUS AIR SPEED OR IN THIS CASE LAND SPEED VERSUS WATER SPEED OF THE RIVER.JUST A THOUGHT. BRIANFirst... on the left side of your keyboard, there is a button that says "Caps Lock" on it. It is right over the shift key. Go ahead and hit that really quick for us.. wink
I did both readings in lakes, with no current and similar conditions. I understand what you mean though.

[LVjetboy]

No solution to your problem Wes, just responding to an earlier post in this thread...
The seperation thing (incoming water is being streched so violently that it seperates the hydrogen from the oxygen) is what they taught us in a short hydrodynamics class that my old pump shop boss required us to take at the local CC for employment. If its wrong let me know, I'd love to call my old boss and the school and tell them they are a bunch of dumbasses. Call your old boss Wsm9808, inform him or the school what you wish; jweeks is correct.
Cavitation is caused by water pressure reduced to vaporization point by flow disruption, etc. (boiling = vaporization as in water vapor suspended, then = rapid collaspe or reliquidation when pressure increased...sometimes causing damage to the surface in contact)
Separating hydrogen from oxygen, on the other hand, is called dissociation...caused by very high temperatures, ionization and/or chemicals processes. Not something our impellers usually concerned with? And a different physical process.
BTW WSM9808, I think you're right on about Jac Sea...(HBM listening?) We have a vacuum of information about jet drive performance and technical information...just word of mouth at best. So we thrash about, trying one thing or another before finally "discovering" what was already known. Depending on who you talk to of course, or if you're in the "racer's" fold.
mr. anal science,
jer
[ August 19, 2002, 02:31 AM: Message edited by: LVjetboy ]

[pops1]

Froggystyle:
Yes.
BTW. Dave, I got my impeller and DPS preloader in the mail today...
I have to say, they look really nice and well finished. I have taken one single aspect of this testing seriously and with no preconceptions of worth based on company or reputation. I have proven only that the stock Berkeley stuff will not do the job. I don't see any improvement I can make on the setup short of adding a Meirsh intake.
This new phase of testing for all concerned will be focusing on my new Aggressor "B" impeller in Mag-Bronze and a DPS cavitation reducer, both supplied by Aggressor in lieu of the SS impeller won in the contest. Dave feels that this will do more for the boat as a whole than the SS impeller will, so we did some horse trading.
I will start a new topic as soon as I start removing the engine tomorrow to pull the shaft for machining. It will be called Berkeley Mods Episode two, and will compare visually at least the four impellers I have currently and the differences between a detailed Berk, stock, A vs. A2 and the Aggressor Mag-Bronze.
Squirts Up!
WesWes we have some Graphite Hi RPM Packing if you want to try- Call Me. Dave

[Froggystyle]

From initial inspection... the packing seems to be graphite stock. That or it just looks all gray and metalic because of the grease, but I think not.
I'll ask Mike today.
Pump is out of the boat BTW...

[wsm9808]

ya know, now that I think about it, I think I already called my old boss a dumbass. Might have had something to do with why I got fired. Guess I should thank him though, after working for him I knew I never wanted a boss again, and opened my own machine shop. Now I'M the dumbass boss. :D

[AGGRESSOR JETS]

Pump is out of the boat BTW...[/QB]If you need help on Machining your shaft or Call-How;s it going!Dave

[liberator21]

HEY FROGGY MY BUDDY HAS A JET WITH ABOUT 900LB OF TORQUE. IT'S A 567CI BBC, HE CAN STAND ON IT AND DOES NOT SLIP THE PUMP. THATS WHAT WE CALL IT , NOT CAVITATING. IT HAS RUN 4.97 SEC. AT 113 MPH ON SDBA CLOCKS AT THE 660 FOOT LIGHTS. IF YOU NEED HELP GETTING YOU BOAT TO HOOK UP DOWN LOW CALL ME 281-705-8821 KEVIN. I KNOW ALOT OF PEOPLE THAT RACE JETS. MIKES PUMP & SPEED IN HOUSTON,TX OR EMAIL GARY SNOW AT SDBA069@AOL.COM GOOD LUCK IT TOOK US TWO YEARS TO KEEP THE BOAT HOOKED THROUGH THE OTHER END.