Educate me - Impeller size

[speedymopars]

OK, I am putting together a new combo for the boat - but I don't know if I should treat the impellor like a gear ratio / stall combo in a car, or is it something different? If I get the projected curve, how can I tell what impellor would best suit the berkely 12-JC?
RPM HP TQ
2K 155 408
3K 239 436
4K 372 488
5K 472 495
5.5K 495 472
6K 501 439

[Sleeper CP]

Someone will post the stock Berkley Chart for you.
You may run a search on it.
Sleeper CP

[Jetaholic]

Here you go:
http://www.***boat.com/forums/attachment.php?attachmentid=38806&stc=1&d=1189398516

[YeLLowBoaT]

you may want to post your boat specs and what you want to do with the boat.

[Squirtin Thunder]

I think you would be very happy with a MPD A impeller

[speedymopars]

It's a 21 foot Daycruiser'ishV hull - Use skiing, cruising and occasionally going fast.
If I read these right, if you make more torque you want a bigger impeller, A2/3/4 (or is that AB??) which acts like a low numerically gear and will give you a greater top speed (and vice versa), correct? I'm still unsure of how to get from that chart to where I need to be. I'm looking for someone to explain it to me.
It would almost seem I would want the C impellor for max top speed, but the A would be better all around? See I'm not understanding fully how it affects things...

[speedymopars]

Am I correct if I said the C would give me quicker acceleration but the A would theoretically give me more speed per RPM?

[Squirtin Thunder]

The bigger the impeller the more forward thrust that is created at a given RPM.
The C impeller would have to turn about 600 - 800 rpm more than the A to equal the same thrust.

[YeLLowBoaT]

big boat that pulls skiers = big impeller.

[ck7684]

If your engine makes it's power at a higher RPM, you will need a smaller impeller like a "C"...in some cases being able to get to this power range will give you more top speed. Say for example that your engine makes 500 hp at 6000 RPM. With an A impeller you wont be able to reach 6000, so you wont be using all the available power, and your speed will be dependent on getting more RPM, which = pumping more water=more thrust...
Hope that helps

[speedymopars]

If your engine makes it's power at a higher RPM, you will need a smaller impeller like a "C"...in some cases being able to get to this power range will give you more top speed. Say for example that your engine makes 500 hp at 6000 RPM. With an A impeller you wont be able to reach 6000, so you wont be using all the available power, and your speed will be dependent on getting more RPM, which = pumping more water=more thrust...
Hope that helps
Yes, I think that does. Trade off between top RPM/MPH and engine acceleration. In looking at it, if I am understanding it, once your HP meets the Impeller RPM curve, you don't go any faster.
With the curve I said,
A2 would give me 5100 RPM
A = 5300ish
B = 5500
C = 6000
Which one accelerates quicker? Which one could have more top speed? Or is it all the same just hitting the engine at a different RPM?
Yellowboat said pulling a skiier I need an A - so an A would deliver more thrust to pull out a skiier? Or would the C just take more RPM to do the same?
Does anyone have the other impellor curves (a2/3/4 AB, etc)?
Sorry for all the Q's and such, I'm really trying to understand it.

[Sleeper CP]

For your 21' Daycrusier an A or A/B would be a good place to start. You can always trim more off an impeller but you can't add it back on.
Don't start with anything smaller than an A/B cut.
How high do you want to rev it?
Sleeper CP
565" Ford Lover

[speedymopars]

For your 21' Daycrusier an A or A/B would be a good place to start. You can always trim more off an impeller but you can't add it back on.
Don't start with anything smaller than an A/B cut.
How high do you want to rev it?
Sleeper CP
565" Ford Lover
Honestly, this combo is good mechanically for a pretty high RPM 7500-8500, KB external pump, really short and light pistons, large pan, etc. Difference between 5K and 6.5K is all a perception issue more than anything else (of course lower rpm is less strain). The cams I have to choose from (IE the ones in the garage), are a hyd 240/248duration (@.050) 510 lift, and a 312/320 duration .670 lift solid roller. The dyno curve I gave was simulated using real head flow numbers with the Hyd cam. I think the roller will be a little too much RPM, and not enough bottom end with the cubes I have in this combo (I'd probably only get 3K RPM out of it).
Are there flow numbers associated with an impeller, IE, a C flows 4000GPM @ 4000 RPM while an AB flows 4000GPM at 3000 PRM or such (made up numbers obviously). This could help me figure out what combo would go faster, assuming GPM = Thrust and speed for a given hull configuration.

[ck7684]

Keep in mind that with a boat, you will always be running a "high" RPM, not just touching it for a couple seconds like in a car...therefore 4000 is fairly high. You dont want to be casually cruising around with the engine reving at 6K all the time...

[Sleeper CP]

Are there flow numbers associated with an impeller, IE, a C flows 4000GPM @ 4000 RPM while an AB flows 4000GPM at 3000 PRM or such (made up numbers obviously). This could help me figure out what combo would go faster, assuming GPM = Thrust and speed for a given hull configuration.
If I were you, I would figure out what the boat will be doing 85% of the time and set it up for that. I thought I read it was a 21' daycruiser. I wouldn't focus on the top speed thing. Put an A or A/B in it and if you want to go faster put a 125-150 shot of Nitrous on it and be happy.:D
Out
Sleeper CP
565" Ford Lover

[speedymopars]

Keep in mind that with a boat, you will always be running a "high" RPM, not just touching it for a couple seconds like in a car...therefore 4000 is fairly high. You dont want to be casually cruising around with the engine reving at 6K all the time...
Good point. *Very* good point.
If I were you, I would figure out what the boat will be doing 85% of the time and set it up for that. I thought I read it was a 21' daycruiser. I wouldn't focus on the top speed thing. Put an A or A/B in it and if you want to go faster put a 125-150 shot of Nitrous on it and be happy.:D
Out
Sleeper CP
565" Ford Lover
I just happen to have an extra (complete kit) 175 shot in the garage sitting there doing nothing that I know will work great, and I currently have an A impeller in my jet now. Certainly will be cheaper to keep what I have for now.
BTW - I love Nitrous
On other boards my tag is
bottles...they're not just for babies anymore
****
Thanks to both of you (and everyone else) for keeping me grounded. uh, watered. rivered?

[ol guy]

quik street relationship to an impeller. A cut 538. c cut 373. hope this helps figure the rpm range and where you're torque will help most with a heavy boat trying to get out of the water. Or up on plain with a skier drowning behind you in the soup.

[bp]

quik street relationship to an impeller. A cut 538. c cut 373. hope this helps figure the rpm range and where you're torque will help most with a heavy boat trying to get out of the water. Or up on plain with a skier drowning behind you in the soup.
what?? :confused:

[Jetaholic]

quik street relationship to an impeller. A cut 538. c cut 373. hope this helps figure the rpm range and where you're torque will help most with a heavy boat trying to get out of the water. Or up on plain with a skier drowning behind you in the soup.
Actually, wouldn't that be the other way around? The A being like a 373 and the C being a 538? 373's are a stiffer ratio than 538's...just as an A is stiffer than a C I would think.

[Sleeper CP]

quik street relationship to an impeller. A cut 538. c cut 373. hope this helps figure the rpm range and where you're torque will help most with a heavy boat trying to get out of the water. Or up on plain with a skier drowning behind you in the soup.
I guess that was humor, but an A is like a 2.73 gear and an D is like a 4.88 I would say:confused: Maybe not, but I think so.
Sleeper CP
Big Inch Ford Lover

[ol guy]

Okay, you guys are trying to say a 2.73 gear will get you off the line quiker than a 5.38 gear will???????????????????. You might as well say a a cut impeller will give you more top end than a c cut impeller will.

[Jetaholic]

Okay, you guys are trying to say a 2.73 gear will get you off the line quiker than a 5.38 gear will???????????????????. You might as well say a a cut impeller will give you more top end than a c cut impeller will.
No, what I'm saying is that with a 3.73 ratio, more torque would be required to get your RPMs up than would be with a 5.38...just like more torque would be required to get your RPMs up with an A impeller than with a C impeller.

[Sleeper CP]

Okay, you guys are trying to say a 2.73 gear will get you off the line quiker than a 5.38 gear will???????????????????. You might as well say a a cut impeller will give you more top end than a c cut impeller will.
Assume you have a high gear only car a one speed. A 2.73 gear will accelerate slower and will reguire more HP to run to 6,000 rpm. If your engine had the power to tun it to 6k you would be hauling a$$. The problem is if you only have 550 HP you will never pull your 2.73 gear to 6k.
Replace those gears with 4.88's. The 4.88's will accelerate the car faster off the line and rev out faster. The problem here is the gears will over rev the engine if your 550HP engine is set up to turn 6,000 rpm's. You'll run out of gear before you get down the 1,320. And if you go out on the Freeway you will be cruising at 65 mph at 4,200 rpm's.
Just my .02
Sleeper CP
Big Inch Ford Lover

[ol guy]

Not going to get in a pissing match here. Hey speedy 21ft cruiser needs bottom end to get going. {short gear} a- cut will get better bight on the bottom end with the torque specs you showed. c cut will get better mph thru the lights {c-cut } period. Call jack at MPD and ask him, he is in costa mesa ca. I'm out.

[speedymopars]

OK, I see where you guys are going
In my duster, with the 8000 rpm 440, I put in 4:30's to go fast in the quarter mile. Vast improvement over the 3.91's I had in there.
Now I have a quick reving 528 with the 4:30's - Now it doesn't matter 1,2,3rd gear on take off - it accelerates the same. This is because the torque is overwhelming. To go faster in the 1/4 mile, I needed to put in a 3.23 gearset to get the top end back, as the 4.30's limited the top speed and I'd run out of gear on the 1/4 mile. Basically I needed to use the slow stock parts to go faster.
Thinking about it, the impellor is the stall, the gear AND the tire.
A "C" has a nice "stall" (let's the motor wrap quick) medium "gear", but no "tire". So in a heavier hull, it won't push enough to get the boat to move initally. OK with a smaller motor that needs the "stall or gear" more than it needs the "tire" but not in a heavier boat. The "tire" becomes less imprtant the faster you go (easier to do a burnout at 5 than at 100).
An "A" has no "stall", no "gear", but lots of "tire", so everything it gets, it moves. In a motor that has torque, that is the same as when I went to the 528.
I think I understand. somewhat. :messedup: :2purples:

[396_WAYS_TO_SPIT]

big boat that pulls skiers = big impeller.
I agree......

[pw_Tony]

OK, I see where you guys are going
In my duster, with the 8000 rpm 440, I put in 4:30's to go fast in the quarter mile. Vast improvement over the 3.91's I had in there.
Now I have a quick reving 528 with the 4:30's - Now it doesn't matter 1,2,3rd gear on take off - it accelerates the same. This is because the torque is overwhelming. To go faster in the 1/4 mile, I needed to put in a 3.23 gearset to get the top end back, as the 4.30's limited the top speed and I'd run out of gear on the 1/4 mile. Basically I needed to use the slow stock parts to go faster.
Thinking about it, the impellor is the stall, the gear AND the tire.
A "C" has a nice "stall" (let's the motor wrap quick) medium "gear", but no "tire". So in a heavier hull, it won't push enough to get the boat to move initally. OK with a smaller motor that needs the "stall or gear" more than it needs the "tire" but not in a heavier boat. The "tire" becomes less imprtant the faster you go (easier to do a burnout at 5 than at 100).
An "A" has no "stall", no "gear", but lots of "tire", so everything it gets, it moves. In a motor that has torque, that is the same as when I went to the 528.
I think I understand. somewhat. :messedup: :2purples:
You sound like a true Mopar or no Car dude.... Nice:)

[Sleeper CP]

I think I understand. somewhat. :messedup: :2purples:
Close enough. Oldguys example would work better if your boat was an 18' racer although he is 180 out on his example.
As Yellowboat said" Big Boat to pull skier, need big impeller"
Start with an A or A/B you don't have a little race boat. You need to move volumes of water to move your big boat.
Sleeper CP
Big Inch Ford Lover

[YeLLowBoaT]

I would start with a AA and cut it down to a 1.5A if needed. I would not go smaller then an A.
I would much rather go a little slower and save the motor, then go a little faster and blow it up.

[ol guy]

That's what i've been trying to tell you and maybe misunderstood but bottom line is you are on the right track. good luck M

[Squirtin Thunder]

My new recovery boat will have a 9.5" impeller and a slightly modified BBF with a peek RPM of 4K this way it can tow anything and almost idel up river if I were to choose to do so. It will be able to tow the heaviest barge up river when current is at max flow 10mph. The big Blue River Jets boat has two pumps pushing two 9.5" impellers, they run to Havasu everyday and anyone who runs the river out here knows that boat is a barge from hell.

[396_WAYS_TO_SPIT]

I think you would be very happy with a MPD A impeller
AGREED;)

[Sleeper CP]

I would start with a AA and cut it down to a 1.5A if needed. I would not go smaller then an A.
I would much rather go a little slower and save the motor, then go a little faster and blow it up.
I'm not sure but I think he would like to see close to his redline from time to time. Will he be able to turn an AA past 4,700 r's.
Sleeper CP
Big Inch Ford Lover

[pw_Tony]

My new recovery boat will have a 9.5" impeller and a slightly modified BBF with a peek RPM of 4K this way it can tow anything and almost idel up river if I were to choose to do so. It will be able to tow the heaviest barge up river when current is at max flow 10mph. The big Blue River Jets boat has two pumps pushing two 9.5" impellers, they run to Havasu everyday and anyone who runs the river out here knows that boat is a barge from hell.
Recovery boat? Do tell...:idea:

[bp]

I'm not sure but I think he would like to see close to his redline from time to time. Will he be able to turn an AA past 4,700 r's.
Sleeper CP
Big Inch Ford Lover
just hit the n2 button, no problem.
you're better off staying under the curve, rather than trimming an impeller that might take you past the hp peak, especially if you're gonna use n2. with an a and a 200 shot, he should be picking up 300-400 rpm. i'd start with either an aa, or the 9.5, see where it lands.

[YeLLowBoaT]

I'm not sure but I think he would like to see close to his redline from time to time. Will he be able to turn an AA past 4,700 r's.
Sleeper CP
Big Inch Ford Lover
I think it would be pretty close to 5k. I know he could spin a 1.5 AA to 5k.

[Sleeper CP]

just hit the n2 button, no problem.
you're better off staying under the curve, rather than trimming an impeller that might take you past the hp peak, especially if you're gonna use n2. with an a and a 200 shot, he should be picking up 300-400 rpm. i'd start with either an aa, or the 9.5, see where it lands.
He mentioned he had a 175HP system just sitting around, so I think he's up for that. I was going conservative on his HP numbers,because they are guesstimates off or a dynomation or simimular program. The engine hasn't been dyno'd and I'm not sure if he is going to run logs or headers in his day cruiser. Therefore, I'm not sure if he can get the numbers he is estimating.
I too think a detailed A would be a good place to start.
Sleeper CP
Big Inch Ford Lover

[Cs19]

just hit the n2 button, no problem.
you're better off staying under the curve, rather than trimming an impeller that might take you past the hp peak, especially if you're gonna use n2.
Are you saying you should stay under your peak HP/RPM "on motor" when on the bottle?:confused:

[Sleeper CP]

Are you saying you should stay under your peak HP/RPM "on motor" when on the bottle?:confused:
I have always wondered if you should over rev the engine when on the bottle or stay at or below. My Bro and I have always chosen to stay at or below the peak off the bottle rpm. It just seems to be easier on the valve train and other parts.
Current engine revs to 7,000, should pull to 6,000- 6,100 off the bottle (MPD A) and pull to 6,800 on the juice. Just my .02
Sleeper CP
Big Inch Ford Lover

[Cs19]

7-800 rpm jump on the nitrous is alot, how much juice?

[Sleeper CP]

7-800 rpm jump on the nitrous is alot, how much juice?
175 shot should take the engine to 1,100 hp.
930 at 6,800 off the bottle plus 175 shot. Engine Rev'd out to 7,000 on dyno 935 HP.
Edit: It should be stated that the above dyno #'s are corrected numbers, so more than likely at the river on a 105-110 degree day I will have to run at least a 200 shot if not a 250 shot to see the power and RPM increase I'm looking for. So it is currently jetted for a 200 shot with 5 degrees of retard for the next time out.
Old system would take an Legand AA from 5,800 to 6,800 on a 250 HP Shot.
That engine combo made 855 at 6,800, so the 250 shot would take it to 1,100 HP.
Sleeper

[speedymopars]

You sound like a true Mopar or no Car dude.... Nice:)
I did buy a non mopar (mustang) once, and those years I learned to really appriciate the Mopar way of doing things. They do it like how I would do it, (esp in the engine department) and keeping everything separate. Easy intake manifold changes (no water or disti), external oil pump, water pump and systems isolated, easy windage tray install, mains tucked into the block for strength (add cross bolts for insane 7000+ HP strength), good oiling system, etc etc etc. Aftermarket blocks further improve on the design.
The engine design is really good, let's face it the same design is still winning in all the top pro drag races. Throw in some Chevy rods, wrist pins and bearings instead of the Mopar ones (to lighten it up), make sure the cubes are up over 450 (small BBM's are too heavy for the cubes), throw away the alternator (which you could tell me was designed by Lucas and I'd believe you) and replace it with a GM Delco, and you have a perfect engine. IMHO of course :D
Love this discussion, I'm learning a lot. Thanks.

[bp]

Are you saying you should stay under your peak HP/RPM "on motor" when on the bottle?:confused:
no, that's not what i said.

[Cs19]

Old system would take an Legand AA from 5,800 to 6,800 on a 250 HP Shot.
Dang I've never seen a 250 shot do anything like that.

[Sleeper CP]

Dang I've never seen a 250 shot do anything like that.
Remember it's an AA so the power curve is real steep. The impeller holds the engine back about 75 hp from it's peak so a 250 shot acts more like a 325 shot when you look at the power curve. (if that makes any since) The engine picks up the Nos power plus the additional power from the rpm gain.
Best that I can explain it.
Do you typically see a 400-600 increase?
Sleeper CP
Big Inch Ford Lover

[Sleeper CP]

Bump with edit:
I too think a detailed A would be a good place to start. An A would turn 5,400 or so off the Nos and 5,800- 6,000 on the juice approx.
Sleeper CP
Big Inch Ford Lover[/QUOTE]

[-XTC-]

On a 2 stage setup (175 1st and 150 2nd) - I saw an increase from 5800 to 6800 on a MPD detailed B.
Darin

[bp]

Remember it's an AA so the power curve is real steep. The impeller holds the engine back about 75 hp from it's peak so a 250 shot acts more like a 325 shot when you look at the power curve. (if that makes any since) The engine picks up the Nos power plus the additional power from the rpm gain.
Best that I can explain it.
Do you typically see a 400-600 increase?
Sleeper CP
Big Inch Ford Lover
well, if you turned an AA 6800, you were turning it 200 rpm faster than we turned an mpd blueprinted A in risky business when we were setting all the pgj records. i'd guess, if you hold it down for 5 seconds, you're running around 120-125. good stuff for a gullwing.

[Sleeper CP]

well, if you turned an AA 6800, you were turning it 200 rpm faster than we turned an mpd blueprinted A in risky business when we were setting all the pgj records. i'd guess, if you hold it down for 5 seconds, you're running around 120-125. good stuff for a gullwing.
You have to remember it's a big old station wagon. Hull and pump only weigh in at 990 lbs. And then the open bow the air doesn't exactly like passing over it.
I have learned in the past 90 days or so that MPDs' pumps are far more efficient than the typical blueprinted pump.
If you would like to ride in a gullwing at 120 plus I'll stand back and watch you. Thank you very much:D
Signi told me for years that he would love to seen our engine in a 450 lbs. hull and see how it performed.
Sleeper CP
Big Inch Ford Lover

[speedymopars]

You have to remember it's a big old station wagon. Hull and pump only weigh in at 990 lbs. And then the open bow the air doesn't exactly like passing over it.
I have learned in the past 90 days or so that MPDs' pumps are far more efficient than the typical blueprinted pump.
If you would like to ride in a gullwing at 120 plus I'll stand back and watch you. Thank you very much:D
Signi told me for years that he would love to seen our engine in a 450 lbs. hull and see how it performed.
Sleeper CP
Big Inch Ford Lover
OK, who is MPD, and how much for the kit?

[Sleeper CP]

OK, who is MPD, and how much for the kit?
MPD: Marine Performance Design (Jack McClure) he has been doing jet pumps in So Cal for nearly 30 yrs or so. His pumps have won the most championships and have been run in the fastest jet boats for years.
His operation is in Costa Mesa Ph. 949-631-2040. You won't find better pump work in So. Cal. Prices vary depending on the work you need. Your application is not a high hp deal so even on NOS you can probably use an Alum impeller.
There are other So Cal shops that can probabaly do what you need done for your 21' Ft day cruiser. It's not like you need a killer race pump to get what you need out of it. But ,he does do the best work you will find.
Sleeper CP
Big Inch Ford Lover

[bp]

You have to remember it's a big old station wagon. Hull and pump only weigh in at 990 lbs. And then the open bow the air doesn't exactly like passing over it.
we weighed my boat in jack's shop about 4 years ago, with everything out of it - i'd stripped every piece of metal for powder coating. the only things were the hull and pump - 865, so you beat me:) .
I have learned in the past 90 days or so that MPDs' pumps are far more efficient than the typical blueprinted pump.
i'll give ya a story. 10-11 years ago, keith ran a "lake layup" daytona with a 496 in the 11 second class, and ubfj with a 200 or so shot. he ended up winning the 11 second championship one year, but took the thing to cfw, put a 400shot in it, which of course scattered the poor thing. he had a 540 built for it, while he started racing the biz. as keith was going to stop racing, dave was building my engine. knowing what was going into the engine, keith kept telling me "it'll make a great 11 second boat", as we both knew the southwind was heavier than the lake layup daytona, not by much, but heavier. the first race of the season, we take the lake daytona back out to ming, and sure enough, the best it can do with the 540 is 11 seconds, so we win that class. next race, we have the sw together, and i run a best of 10.12 at 103, which was faster than his lake daytona ever ran. granted, i had more hp than him (his 540 had brodix heads, sheetmetal intake, twin big doms, i had 2 750s), but we're talking almost a full second difference and higher speed out of a southwind tunnel, compared to a daytona.
the difference? my pump had been blueprinted by mpd in 1985, then freshened before we ran the new engine. his pump was not blueprinted by mpd, nor did it have mpd hardware. mpd has been in the same location for over 35 years.
If you would like to ride in a gullwing at 120 plus I'll stand back and watch you. Thank you very much:D
aahhh, no thanks. my only point was that AA versus mpd prepped A stuff. the biz weighed 365 completely bare (no pump), and ran 132-134 in the 7.80s, turning that impeller 6600.
Signi told me for years that he would love to seen our engine in a 450 lbs. hull and see how it performed.
Sleeper CP
Big Inch Ford Lover
ronnie gave me crap everytime he saw me about that, as did a few others. there are several reasons i've continued to run the southwind.
ask ron about his trip to sitc, running the 7.0 class with his 460" engine. nobody, but NOBODY, believed he was running 7s in arkansas with an engine that tiny. there were reasons he could do that with no n2 i had several people tell me the same thing in marble falls 3 years ago.. "you can't run 10s here in a southwind with no n2". ok. qualified #5 out of 26 with a .03. i think you're starting to get the drift...:D

[speedymopars]

MPD: Marine Performance Design (Jack McClure) he has been doing jet pumps in So Cal for nearly 30 yrs or so. His pumps have won the most championships and have been run in the fastest jet boats for years.
His operation is in Costa Mesa Ph. 949-631-2040. You won't find better pump work in So. Cal. Prices vary depending on the work you need. Your application is not a high hp deal so even on NOS you can probably use an Alum impeller.
There are other So Cal shops that can probabaly do what you need done for your 21' Ft day cruiser. It's not like you need a killer race pump to get what you need out of it. But ,he does do the best work you will find.
Sleeper CP
Big Inch Ford Lover
Given the fact that he is less than 10 miles away from me... I think the choice is clear. Thanks!