ANYTHING NEW ON THAT DUAL JET DRIVE PUMP

[THE BOSTON SIDEWINDER]

HEY, IS THERE ANY NEW WORD ON THAT DUAL JET DRIVE ON THE SINGLE ENGINE, IS IT PROGRESSING OR ARE THERE SETBACKS?...BILL.

[Lightning]

I'm pretty sure they offer it in a setback :D .

[Hallett19]

I met a ***boater at OP6 who had the dual drive in his 21 foot daycruiser with a mildly blown/basically stock 454. He had duel jets/place diverters and that boat pulled so damn hard !!!! If you like pull and speed, the dual jet conversion on your boat might be where its at.

[FastRat1]

anyone got pics???...who's makeing it??...more info...PLS
Ron

[Unchained]

When I was at Red Bluff in May I talked to a racer who told me he intended to put a dual pump in a 19' Stealth by widening the hull enough to accept the intake.
He is a current record holder and really knows his stuff.
He relayed that the top speed may not increase significantly but the accelleration would be extreme.
Mark

[superdave013]

I have some pics that I took some time ago of the dual set up that's in the 23' Renegade. Look in the media center in my gallery.
They were taken before it was complete. I saw the boat again yesterday. All's well with it and it works good.

[superdave013]

opps, they at ***boatpics.
I'll make it easy for ya.
http://www.hotboatpics.com/pics/data/500/48gear_box1-med.jpg
http://www.hotboatpics.com/pics/data/500/48transom-med.jpg
I'll try to get over there sometime next week to get some new photos. It looks pretty cool with the diverters and nozzels installed.

[Cs19]

Unchained:
When I was at Red Bluff in May I talked to a racer who told me he intended to put a dual pump in a 19' Stealth by widening the hull enough to accept the intake.
He is a current record holder and really knows his stuff.
He relayed that the top speed may not increase significantly but the accelleration would be extreme.
Mark was that guy you talked to harold bruce? last time i was over at his shop he was planning on doing that in that 19 daytona and was working on that helicopter engine/dual drive deal.

[Bense468]

they are supposed to run some capsule deal I thought. Anyway thats what he told me a while ago.

[superdave013]

cs19:
Unchained:
When I was at Red Bluff in May I talked to a racer who told me he intended to put a dual pump in a 19' Stealth by widening the hull enough to accept the intake.
He is a current record holder and really knows his stuff.
He relayed that the top speed may not increase significantly but the accelleration would be extreme.
Mark was that guy you talked to harold bruce? last time i was over at his shop he was planning on doing that in that 19 daytona and was working on that helicopter engine/dual drive deal. Harold set up the boat in the above pic. He ws telling me about his plans for the daytona also. I think he was talking capsule too.

[Cs19]

I havent spoke with them in a while, glad to hear hes putting in a capsule, need to see more of those out there, and i think after someone does run one and remains competitive more will do the same and keep the fast jets safe and returning to the races. That must be one helluva project cutting the hull down the center to widen it to fit that dual intake jet.hope to see them back out at ming next season. :)
Whats the story on that one guy who was having a jet(forget what hull) set up by papp with a Brad Anderson motor in it?

[Johnwithjm]

That would be Frank Nagore. He will be at the next NJBA race in Sept.

[Cs19]

cool. good to hear he is back.

[Unchained]

cs19
Mark [/qb]was that guy you talked to harold bruce? last time i was over at his shop he was planning on doing that in that 19 daytona and was working on that helicopter engine/dual drive deal. [/QB][/QUOTE]
He's the man.

[Cs19]

thought so. he was origonally going to do the rigging on my 19 daytona, It didnt work out to say the least. Its nice to see your boat is up and running unchained, good job!

[THE BOSTON SIDEWINDER]

SUPERDAVE013- I WAS WONDERING IF THIS SETUP IS ANYWHERE NEAR THE PRODUCTION STAGE? OR IN THE FUTURE? HOW MUCH WOULD YOU EXPECT IT WOULD COST FOR THE DRIVE SET-UP? IT SEEMS LIKE IT WOULD WORK REALLY WELL ON A BIGGER HEAVIER BOAT. THEY SAY USUALLY A JET IS ONLY GOOD FOR A BOAT LESS THAN 24 FT OR SO. DOES THIS SET-UP NEGATE THIS IDEA? THE PICS LOOK PIS*ER, KEEP EM COMING...BILL.

[Hustler]

I believe that the complete set up for this is around 10k. As far as being good for the larger boats I know there is a 25' Carerra with a turbine motor in it and it pulls hard out of the hole, from what I have heard though is you need some pretty decent power to make the twin pumps run hard

[hboldno7]

heres a pic of the turbine powered 28 Cararra with the Dual jet setup. It looks like its ready to take lift off.
http://www.***boat.com/image_center/data/521/334DSCN0469.JPG

[1slowboat]

jawdrop i would say that that looks like some hell of alot of torq.... out of the hole and gone.... it looks like...nice pic ive been reading about the 2 pumps in a boat and just wounder if the pump on the drivers side turns the oposite dir? :D :D

[Backtanner]

1slowboat:
nice pic ive been reading about the 2 pumps in a boat and just wounder if the pump on the drivers side turns the oposite dir? :D :D I'm thinking if you did, wouldn't you need to design a opposite rotation impeller too.

[THE BOSTON SIDEWINDER]

IT SURE MAKES THAT 'OTHER KIND' OF BOAT STEER EASIER WHEN THE PROPS, AND DRIVES ARE COUNTERROTATED! THANKS FOR THE PICS. NOW I JUST HAVE TO SAVE UP FOR A 22,000 HP TURBINE ENGINE. WHERE WOULD YOU BUY FUEL FOR THAT? MAYBE AT LOGAN AIRPORT THEY HAVE AN EXTRA LONG FUEL FILL NOZZLE TO REACH DOWN THE THE WATER'S EDGE, NOT BAD JUST $15 A GALLON, WELL DAMN IT I CAN DREAM...BILL.

[pops1]

[QUOTE]Originally posted by superdave013:
[QB] opps, they at ***boatpics.
I'll make it easy for ya.
Aggressor will be Testing again, both the dual in the Schiada & the Tunnel. So far we have run Gear Box, & Chain Drive, this time we will be running belt drive. Our Canadian Dealer has ran the Belt Drive Dual on both Performance & JR Pumps with great sucess.
Upon completion of this we hope to release the 12" Dual Drive @ $8300.00 Complete through our Dealers.
3 sizes 7" JR Drives impellers Drives, 8" Mid Impeller Drives & our Performance 9" & 9 1/2" Impeller Drives.
Several other units of ours will pop up shortly. Dave-

[superdave013]

pops1:
[QUOTE]Originally posted by superdave013:
[QB] opps, they at ***boatpics.
I'll make it easy for ya.
Aggressor will be Testing again, both the dual in the Schiada & the Tunnel. So far we have run Gear Box, & Chain Drive, this time we will be running belt drive. Our Canadian Dealer has ran the Belt Drive Dual on both Performance & JR Pumps with great sucess.
Upon completion of this we hope to release the 12" Dual Drive @ $8300.00 Complete through our Dealers.
3 sizes 7" JR Drives impellers Drives, 8" Mid Impeller Drives & our Performance 9" & 9 1/2" Impeller Drives.
Several other units of ours will pop up shortly. Dave- What one worked the best? That chain drive sounds kinda cave man to me.
Can you post some pics of your stuff? So far we have only see Harold Bruce's set ups (very nice work too). We would love to watch the progress on yours too.

[Jet2Riv]

Hallett19:
I met a ***boater at OP6 who had the dual drive in his 21 foot daycruiser with a mildly blown/basically stock 454. He had duel jets/place diverters and that boat pulled so damn hard !!!! If you like pull and speed, the dual jet conversion on your boat might be where its at. Hey Hallet19, Glad you enjoyed the ride.Hope you had a good summer.
http://www.***boat.com/image_center/data/521/265DSCN0059-med.JPG
I have had my Dual drive for 2 seasons now and love it. Here are a few pics from Havasu this summer
http://www.***boat.com/image_center/data/521/265DSCN0161-med.JPG
Here is a dual drive wheelie jawdrop
http://www.***boat.com/image_center/data/521/265DSCN0173-med.JPG
You can contact Harold at R&D Marine (714) 993-2664 for information about Dual Drives
I will try to post some more pics
Dave

[Jet2Riv]

Here are a few roost pics. I will try to post some more.
http://www.***boat.com/image_center/data/521/265DSCN0517-med.JPG
http://www.***boat.com/image_center/data/521/265DSCN0535-med.JPG
http://www.***boat.com/image_center/data/521/265DSCN0558-med.JPG

[flat broke]

Jet2,
I saw your boat at Sandpoint at Op6, but didn't get a chance to stop by and say hi. How much HP are you pulling, and what kind of RPM are you seeing? Can you give us a little more backround on the setup like the size of the impellers, RPM/MPH sats etc?
Thanks,
Chris

[THE BOSTON SIDEWINDER]

I REALIZE YOU HAVE TO PAY TO PLAY. WHAT AN IDEA, THIS WAY I COULD STAY WITH A JET DRIVE BOAT, AND MAYBE HAVE A CABIN(THAT MY WIFE WOULD LIKE) THE BEST OF BOTH WORLDS. A LOT OF THE JET DRIVE INFO STIPULATES THEY BE USED IN A BOAT UNDER 25 OR SO FT. THERE IS A COMUTER BOAT(40' TUNNEL, THAT HOLDS 100 PEOPLE) THAT REALLY BLASTS ON BOSTON HARBOR THAT RUNS 25 KNOTS WITH A PAIR OF GOVERNED 24 CYL ENGINES WITH INTERCOOLER/AFTERCOOLERS! MAYBE JETS WILL BECOME MORE POPULALAR IN THE NEW MILINIUM SO WE DON'T SEEMLIKE SUCH A RARE BREED...BILL.

[beached 1]

Jet2Riv:
Hey Hallet19, Glad you enjoyed the ride.Hope you had a good summer.
I have had my Dual drive for 2 seasons now and love it. Here are a few pics from Havasu this summer
You can contact Harold at R&D Marine (714) 993-2664 for information about Dual Drives
I will try to post some more pics
Dave I also would like to thank you for a ride in your boat at OP6. That thing pulls HARD!
If I rmemeber right, you weren't running a blown set up of any kind. It was a very peppy sounding BBC nevertheless. I also noticed that you weren't pulling more than about 4600/4800 RPMs on top end, but I could of swore you said you were running 2 C impellers. So, it's gear reducted or? Or was I drunker than I thought. :D
Anyway, thanks for ride. I want twins for my Spectra20!

[THE BOSTON SIDEWINDER]

I JUST GOT HOLD OF A 502, ROLLER, 4 BOLT BARE BLOCK W/ CRANK. HOW WOULD THAT DO WITH A WHIPPLE CHARGER IN SOMETHING LIKE THAT 28 CARRARRA?( OR ANOTHER BOAT LIKE IT WITH A CABIN)?...BILL.

[pops1]

Several other units of ours will pop up shortly. Dave- [/qb][/QUOTE]What one worked the best? That chain drive sounds kinda cave man to me.
Can you post some pics of your stuff? So far we have only see Harold Bruce's set ups (very nice work too). We would love to watch the progress on yours too. [/QB][/QUOTE]
The Quite Chain System we ran on spray lube only I don't get the caveman bit- Chains have stayed up with any other form of transfer. Pick up a moorse book and look @ quite chain! I got turned on to this by a friend who makes big transfers for the offshore racers. Our final Intent is oil bath when finished. The chain stayed cool enough to put you hand on and hold after running several times around the entire distance of Elsinore's shoreline which must be 3 miles or so around.
Its Very Quite and you have no noise transfer like you have with Gears.
In Canada our Distributor just completed testing the new Belt Drive system on 600 H/P Performance Drives. This test showed no stretch at all to the belt and was ran very hard.
The Schiada which is over 5000 pounds we modified the split/intake and re-ran, 59.7MPH @ 4900 RPM's on the Casale Gear Box. Very small impellers C/D cuts. This time we will run on the same Good Year Belt Drive system that canada ran (JET CRAFT) underdriving the pumps to run larger impellers.
Andy @ Casale has made us new gears for further testing. Tom Papp has been helping us make some calls. Our Dual JR is being re-tooled right now to a 8" Impeller to handle a sound Smallblock motor.
Canada also ran JR 7" twins on belts @ 550 H/P and the pump fell short on handleing the bigger horsepower- (why we are building the 8" unit).
The 7" unit has been strong from 40 to 200 H/P as a single. Rotory Motors are also waiting test time up to 350 H/P @ some 400 pound weight reduction with a big increase in torque.
A big fire, combined with a move, puts you backwards and its hell to catch up.
I would love to post Pictures, as of yet not one has worked. Our new catalog shows both Performance Dual and Jr Dual photos. Untill I can get someone to teach me the system on posting photos online, Im stuck!
I also provided a protounit for a split Tunnel Boat- Blown Alcohol, I have not heard further on this unit.
Dave

[jetfan]

I have driven a few of the Dual Drive jet boats, and I can tell you that they perform great. They have great torque out the hole,they get outstanding gas mileage which makes the engines run at a lower rpm, and they are simply the best way to go. I'm going to sell my 19' jet, and then outfit a new 21'-23'boat with a Dual Drive next winter/spring. So if anyone out there is looking for an impecibly maintained 19'jet (454 chevy, hydraulic place diverter), send me a note.

[LVjetboy]

I welcome any and all new ideas for pump technology. New ideas take time to mature that's a fact. Give time to grow and prove.
That said, at some point, the question becomes, does this make sense? The latest dual pump drive design been around not long, maybe a year...still evolving. Getting better I'm sure. Now I think it's time to question.
Consider, if one o/b is good, is two better? If two is better, is three the best? Well then, how about four or more? At what point does lower unit drag friction loss and drive weight outweigh the benefit of more drives?
Jets have similar trends. Yet the internal flow losses from intake and pump housing water drag far exceed the o/b. So too I'd guess the drawback of multiple jet drives. Slow speed acceleration a payoff for heavy boats. But top end? Well...maybe that's why it's reported that multiple drives love the hp? Because their high speed efficiency sucks?
Consider the alternative: A larger pump. It's a fact with enough hp you can drive your existing pump way above pump design point. So go to dual drives and double your losses? A bandaid fix to off-design pump operation if you ask me. How about redesign the pump (larger) to handle the hp more efficiently? This better(?) solution not done because of money concerns.
Yet the best and most sensible solution?
I'm open to debate...right now thinking dual jet drives aren't best for most jets. Especially small jets wanting to go fast. I'd like to see hp/speed comparisons. I think what we really need is different pump sizes to accommodate more hp without an efficiency hit.
jer

[pops1]

I'm open to debate...right now thinking dual jet drives aren't best for most jets. Especially small jets wanting to go fast. I'd like to see hp/speed comparisons. I think what we really need is different pump sizes to accommodate more hp without an efficiency hit.
jer [/QB]We make a 7" impeller Drive called JR,we are finalizing a 8" impeller unit, and make 2- 9" Drive units. We are under test with a Dual 7" Drive and a Dual 9" Drive.
What is the market -I do not know "YET"- what is the efficiency factor, so far very good. What is the race factor - With development very strong. We have learned a lot to date in limited testing.
Today if you want a efficient boat combo (fuel efficient)with high output thrust- Dual looks good.
Some neg's. have been identified in our first design on the intake- It hits a speed wall much like we found in another pump design. Its just development!
I find the dual prop guys have not yet sorted it out completly. I have talked with several on there programs. When it is sorted out, we will see safer, more consistent, & quicker E.T. and speeds "that much I am sure of".
As to Jets & your size pump, We make Impeller's that Fill the Bill. I have yet to find anyone that can efficiently pull our 9 1/4" impeller, or overstuff the 11 vane bowl. When that happens we have other impellers and Bowls tested/tooled & ready.
Your point is also valid- Todays 9" Impeller or some call it 12" pump (Bowl Size) made by most mfg's is the same impeller ran from 350HP to 2500HP. That is a monster stretch and proves to me it can not be as efficient as somthing between say "A & F" & "G to P" as a example.
What you must understand is this industry set dormant in design for some 30+ years as far as development goe's. Berkeley did it up untill it sold that long ago. What did happen to make it somewhat stay up with the times is both the Jet Performance Builders improved hardware and Detroit kicked up the Torque on the motors.
I do think Dual Drive Jets will find a nitch, both in market and in Racing and further think both prop & jet will have new classes setup just for twins. It is being discussed right now for props.
My question to you is- do you not think perhaps 2 smaller impellers will not handle water more efficient then one bigger one. I do agree that Dual Jets are not necessary on 99% of todays Jet market, yet I don't think that a 9" pump is required on all Jet Drives- Time will tell.
Dave- Aggressor Jets

[THE BOSTON SIDEWINDER]

POPS1...BOY IT'S HARD TO PLAN SOMETHING WHILE YOUR DEALING WITH CUTTING EDGE TECHNOLOGY! IN A COUPLE YEARS I JUST WANT TO HAVE MY BULLET PROOF WILD 502 ROLLER BUILT UP TO PUT INTO A 25 FT OR SO CABIN JET BOAT. I THINK IT MAKES SENSE TO DO A DUAL FRIVE, EVERY OTHER VENUE OF MARINE PROPULLSION IS GENERALLY 2 PROPS AND/OR IMPELLERS. IS THAT LOGICAL? THANKS..BILL.

[pops1]

EVERY OTHER VENUE OF MARINE PROPULLSION IS GENERALLY 2 PROPS AND/OR IMPELLERS. IS THAT LOGICAL? THANKS..BILL. [/QB]Funny story- We were developing a v6 jet drive under a mutual agreement with Wellcraft. Aggressor wanted & assumed all costs of development as it was our design & we retained the right of design. We first approached the problem the same way as our counter parts did, put in a 12"drive(9"impeller)with a big cut.
Note we were aware this had failed by (3) other pump co.s prior, but we were looking for a base.
Got our base- next we started shutting down the pump in flow volumn.We used a very shut down 9 Vane bowl based on our current unit, I get the brain storm to have our tool engineer make us a shut down version of our 11 vane bowl.
It fell on its rear, yet not knowing why!
When I get back I took the current 9vane
bowl and the new 11 vane bowl to have flow tested. Rick Green of Weilder Engr. was there and we flowed both of them. What ended up Blowing my mind was the 11 vane outflowed the 9vane by
some 58cfm, yet had 2 more pounds of metal in it.
I turn to Rick and say HOW CAN THIS BE! (What that did was open up the oldest Ford/Chev disagreement of big port volumn flow vs small port controlled flow)
Rick who loves to spank Chev's with his Ford's- Grins at me and say's see "Bigger is not Better"
This started a complete re-thinking with All involved in Aggressor, and led to several disputes with others in the industry as
to our methods/analysis among other things.
To date that analysis has held true for us in several fields. Today I do not recommend our 11 Vane Bowl to anyone less than 650 HP & for E.T. Only with our Impeller. Our Impeller has a increased dig & flow rate & is looking for more water also. The Bowl in all Tests wants water- It E.Ts yet will not carry the MPH of our 9 Vane.
It flows quick & leans on the motor hard.
Dual Drive is being tested in a lot of configurations- Is it for Giant Torque Motors @ Low Rs or for Hot Drag Boats-
Load, Draft Angles are all walls which must be confronted. We had several set backs in our program, yet we have taken the time to identify & overcome the current problems. What we are looking for is net yeild in HP to Performance based on a list of factors.
We started to get involved with a fuel boat in Dual and are now convinced to go it a little slower on that development.
By the same token I just talked to someone developing a new Twin Prop Drive who feels the current development and angles are not yet right.
His Drive will be based on his thinking. We will see!
Heck, we released 35 JR Drives based on the need to develope a smaller pump line.
We have had very sucessful testing for 6 years yet- do not plan the actual release of production units untill early 2004.
Multiple design changes have occured on the JR Unit while in R & D.
I have more calls on this Drive then I can count/name calling too! I do know when we
release this unit in several configurations,
The whole team will be proud of what we accomplished. Dave

[LVjetboy]

Dave, you ask me if thought two smaller impellers would handle water more efficiently than one larger impeller.
I think no. And my focus in this issue and any new pump design is top speed and efficiency, two key weak points with the typical pump design that's been around forever. I think a large pump will be more efficient than two smaller pumps for the same thrust. Here’s why...
One of the biggest losses in a jet pump is drag from water flowing past the walls of the pump intake, bowl housing and vanes, and nozzle. This loss directly related to both speed of water flow and total surface area, among other things. For a typical jet running 60 mph, internal pump flow can exceed 100 mph as the water accelerates and flows through the nozzle. As engine power goes up, these losses become huge, in the end limiting a jet’s practical top speed. Operating the pump way off efficiency or design spec.
Like hitting a wall, at some point more speed requires an unreasonable increase in power. Imagine how fast internal pump flow is for a 140 mph jet boat? I think this is why few jets exceed 150. Yet props, not fighting pump flow losses and housing drag, can top 200 mph. Yes there's dual prop schemes that seem to do well. But for v's and i/o's, only drag from the hardware hanging down (shaft and support or lower unit) is doubled for dual drives and that drag related to hull speed. For jets, the additional housing generates drag at hull speed ++, a bigger hit compared to props. And doubling that hit accents the "wall" even further.
So how to put more power to the pump for more thrust yet limit losses?
Strapping two pumps together with a gearbox gives twice the thrust if you have twice the power to drive it. All that without increasing internal flow speed. A good thing. But this scheme also doubles internal surface area effectively doubling flow losses. A very bad thing. Especially considering pumps are inefficient designs in the first place. That combined with gearbox losses and extra weight makes for a very inefficient design. And if you don't have twice the power to match dual impellers to your engine's peak power, then cutting the dual drive impellers to engine match gives you twice the "off-size" impeller efficiency hit too.
So then consider a larger pump. You mentioned the 9" impeller equates to a 12" pump housing...a standard today been around forever. Some mfg's make a 9.25 and 9.5, but that's about it right? What about a 10 or 10.5? To me that would qualify as large. A contender for breaking the 170 mph barrier?
A larger pump can also increase thrust without more internal flow speed. But internal surface area will also be somewhat more than current designs. However, if the larger pump is sized to flow the same as the dual pump scheme, internal surface area of the larger pump can be as much as 30% less* than for dual pumps. This is not trivial. And this is why I think a larger pump would be significantly more efficient at turning power into acceleration and speed. Not to mention the single larger pump would be lighter than dual pumps and have no gearbox losses.
Yes, I think a dual drive will have awesome low speed acceleration. But single jet pumps are also known for acceleration compared to props. What is lacking is efficiency and top speed. I'd like to see new designs addressing those two points. Why not a 200 mph pump design??
All that said I give credit to mfg's like Aggressor who explore new designs and further jet technology. It's hard to respect a company satisfied with marketing the same 30 year old pump design.
jer

[UBFJ #454]

jer -
I agree with what your saying. For the last 2 years we have been R&D'ing what it would take in terms of hull, motor and pump & its hardware designs to build a true Top Fuel Jet.
Our current thinking regarding pumps for a TF'er is :
1) There currently is no pump commercially available today (at least that I am aware of) that can run and stand up to/"live" with the torgue & Hp that a fuel motor will generate. Current designs are limited to something like 3,000 Hp and below.
2) The amount of thrust required to push a jet dragboat into the 200+ mph range safely cannot be generated by any of todays single pump designs.
and,
3) While a dual pump system will increase the amount of thrust generated, the mechanical woes and safety issues (principally steering & maintaining equal loading of the pumps) alone of a dual pump system in the Fuel Boat environment are, to say the least, not trivial and, in my mind, make it undesireable to go that route.
The above combined will what you have stated in your post (our calc.'s yeild results similiar to yours) are why we are currently pursuing the bigger, single pump approach.
My comments here relate only to single vs. dual pump setups in very fast dragboats ... in no way am I bad mouthing the dual pump setups being brought to the market. I think that their viability , the dual pumps, will be proven in their application in larger recreational boats and possibly in big offshore racers ... just not in smaller, very high speed dragboats.
I too commend those doing R&D and bring these dual systems to the market at affordable prices for it is through such efforts that new generations of pumps, both single and double, will evolve.
jak

[miketsouth]

LVjetboy:
One of the biggest losses in a jet pump is drag from water flowing past the walls of the pump intake, bowl housing and vanes, and nozzle. This loss directly related to both speed of water flow and total surface area, among other things. For a typical jet running 60 mph, internal pump flow can exceed 100 mph as the water accelerates and flows through the nozzle. As engine power goes up, these losses become huge, in the end limiting a jet’s practical top speed.
jer Hey Jer. Long time no argue. But i have to disagree with this statement. The first part cannot be argued. It is correct IMBRHO. On the other hand, the losses are not the speed limiting factor.
The way i see it is that the friction losses exist at any speed. The 'wall' happens at around 60mph.
I see the pump like throwing bricks. More horsepower ( :D :D :D ) more bricks more acceleration. Up to when you start to move and run into the bricks you have to pickup, bring to your speed (slowing you down) then re-accelerate and discharge.
I consulted some hair-brained physics geeks at the university where i work. they knew what i was talking about. Same problem with theoretical space travel at high speeds using sparce particles (free hydrogen) accellerated by some mechanism. Happened WAY before the limiting speed of light came into play. they said that the accellerating mechanism had to be always going faster than the particle was going by.
think of it. when getting out of the hole ALL of the impeller is moving faster than the water. As you start to move faster the water at some point is moving faster than the impeller, especially on the inside. i dont know this but this may be one of the impeller guru 'secrets'. that is to shave away some of the inside of the leading edges of the impeller.\
There is no doubt that there is more to this. Upon my presentation of my theory alone the velocity of the vehicle is limited by the velocity of the effluent. This seems to be true, but it is not. It just seems to work out this way.
At any rate, May your boat be fast and your pump efficient and your ride safe.
mikeT

[HammerDown]

A response to the last 3 posts...erha...OK! :confused: :p :D

[miketsouth]

HammerDown:
A response to the last 3 posts...erha...OK! :confused: :p :D Hammer, i know you are one of them 'torque' guys.
but
That was not a response to the posts of great people giving information and real data on the effects of the dual drives .
That was me saying hey to Jer.
[ September 26, 2003, 10:48 PM: Message edited by: miketsouth ]

[LVjetboy]

Bear, interesting we came to the same conclusion considering different backgrounds. That 30% I based on a simplistic pump model as a cylinder and common cross sectional areas (for same flow rate). But I wouldn't be surprised if actual internal pump surface areas in the same ballpark for dual vs single pump design.
Mike glad to see you here.
I agree, internal flow friction losses certainly exist at any speed. What we call the “wall” is somewhat relative to both setup and power versus speed trade-off. The “wall”, just a way to illustrate that these losses are not a direct or linear one-to-one function of flow speed but more like a cubic function. Similar to hull drag losses. If these losses were one-to-one there’d be no wall. So the internal flow speed versus drag loss curve plateaus. Where you place that limit or decide the curve has reached a plateau (the wall) is a matter of judgment. I picked 150 mph because even a tweaked race pump of the old school design is pushing the limits at this speed. That’s not to say your average jet boat with a stock pump running 60-65 will not need a significant jump in power to run 70 or 80 mph. But just that a tweaked race pump has a higher wall than the stock pump.
On the “slowing down and re-accelerating thing.” I don’t agree. Water for the most part is incompressible. If your hull intake cross sectional area is the same as your impeller face cross sectional area, then intake flow speed will be the same as impeller inlet speed no matter the reference system. (i.e. hull or lake reference system) This is a function of pump and intake geometry and the incompressible property of water, not related to hull speed.
In other words, no matter if you’re launching out of the hole, or tied to the dock, or at top speed, you will not be “running into bricks” or slowing down your intake flow as it travels to the impeller.
Assuming a fully loaded impeller at full throttle, intake flow speed relative to hull should be nearly the same on launch as it is at top speed. You can’t stuff more flow into the intake than your impeller rpm and flow rate requires. Water is incompressible. If you try to stuff more water in your intake than is needed, say with a deep loader and shoe, at some point extra flow will spill out and not be used. So your hull slows to the speed that feeds the impeller what it needs and your intake maintains the flow rate your impeller requires. At this point your loader and shoe drag will also add significant drag losses on top of your pumps normal internal flow losses. But these losses are not from slowing water down or bringing water up to your speed.
Likewise the speed of water flowing through the impeller is mostly independent of hull speed...a matter of rpm. And rpm changes little with hull speed.
As for the velocity of the vehicle limited by the velocity of the effluent or nozzle discharge velocity? This a well-known fact for both jets and rockets. Or brick throwing if you like that analogy. You will never exceed your exhaust or discharge velocity or brick throwing velocity. As you approach 100% efficiency and no drag loss (in a vacuum like space for example) your vehicle velocity will approach your exhaust velocity over time. But our jets are far from that environment. That’s why it’s not unusual for the nozzle exit flow to be 100 mph when the jet boat hits a wall at 60 mph. Water friction losses are HUGE be they just hull or both hull and pump internal drag losses.
jer

[miketsouth]

I somewhat understand the water being incompressable, and thus the average vector velocity thru the pump is 'sort of' proportional to cross-section, the final cross section smallest at the nozzle, largest at the intake. I suppose much of the losses occur near the water/metal boundries where the water doesnt move as fast as water in the center of the cross section. So far so good.
In other words, no matter if you’re launching out of the hole, or tied to the dock, or at top speed, you will not be “running into bricks” or slowing down your intake flow as it travels to the impeller.
The observer moving with the boat, only looking at the water speeds in the pump doesnt see much change. He might see some change of pressures in the intake, but the water speeds are about the same.
but i think the observer using the river as a reference point starts to see the relative speeds of the water in the pump go haywire as the boat speeds up.
As the boat goes by at 60mph that 100mph exit stream is only moving at 40mph now. That water in the intake that was moving at some speed while the boat was standing still is now seen with no speed relative to the river just before it hits the pump, then going BACKWARDS as it enters the pump and then leaving the pump at 40mph
I wonder if one could magicly feed the pump water that moved with the boat if that same wall would exist. Would that same property of 'vehicle velocity never exceeding the ejecta exit velocity' still hold true, or would the boat accellerate until friction and thrust were balanced?
It doesnt seem so. I dont know. So what do you think? I know: you think i got too much time on my hands... well i do. The water here is AFU due to the rains and hurricane and i want to boat some kind of bad.
miket
[ September 27, 2003, 06:58 AM: Message edited by: miketsouth ]

[UBFJ #454]

jer - Similar conclusions ... Different backgrouds ... Not really too suprising is it ... Afterall, physics is physics and mathematics is mathematics and we both use them in problem solving.
Nozzle exit velocity ... and the mechanical, strength of materials & stability considerations is exactly why I'm going down the path of the larger, single CNC'd billet pump design for very high Hp to achieve very low ET's.
Your comment about the cross-sectional area of the intake is true at low speeds, but, as one goes faster and the hull rises (amount & angle differ for every hull and its hardware setup) the more important cross-sectional area is that of the intake "tube", that which comes after the actual intake and before the impeller. Keeping that tube full so that the impeller always sees a full charge (complete face of water) being presented to it is why loader design is so important ... that's the job of the loader (some say scoop) ... to manage the water being fed to the impeller so as to always keep it fully loaded.
From what we're currently going through, I am convinced that there is just as much "Black Art" to loader design as there is to cutting impellers, that is if your really going to get everything you can from your pump in a racing environment.
jak

[LVjetboy]

Mike, you bring up some interesting points.
I suppose your brick picking up analogy could fall under intake losses, but really doesn’t seem to fit there. Maybe not a loss...but some limiting wall of physics as you suggest like vehicle speed will never exceed exhaust speed?
Let’s assume for a moment it is the limiting speed wall for a jet. A wall not related to pump internal flow losses, or hull drag, but a wall that kicks in when lake water is forced to decelerate as it enters the intake. A wall that happened even if the rest of the pumping process was frictionless. If true, this would happen when boat speed exceeds intake flow speed. Now I don’t know what normal intake flow speed is, although I could estimate if I knew a typical intake cross section area. Don’t have that handy. But if I add more power and spin my impeller faster, my intake flow speed goes up. So also the point where lake water must be decelerated as it enters the intake. The running into bricks thing?
So why would there be a wall if I can simply add more power to up my intake flow speed by the same amount and remove the wall? Impeller curves do show a tapering-off of the rate of change in rpm with the rate of change in power. Although gradual, the taper-off does eventually limit how much more intake flow speed I get with added power. Is that taper-off related to the picking up of bricks or causing a wall?
I think impeller curves are typically from data with no pump intake movement. Whatever the physics behind the tapering off in the impeller curves, I don't think it's related to picking up bricks. And, since I'm assuming my pump loss-less in this example my impeller curves would most likely be straight lines. So also the curves for intake flow speed as a function of power input. No more wall. Just add power and go!
But in reality, impeller curves do taper from flow losses whether the intake is moving or not moving. And this behavior does add to total pump losses. When combined with internal flow losses...and finally hull drag...makes a wall. So I'm not buying the brick thing yet.
:)
Where do I think most pump internal losses occur? Probably in and around the impeller. Excluding the impeller, just talking intake, bowl (vanes) and nozzle, I’m guessing within the vanes. Friction, profile and viscous. Vanes have a lot of surface area, and the flow is both accelerating and changing direction.
But this just a guess.
A side note on reference systems: Either a pump fixed or lake fixed system will work, and if applied correctly, both will give the same answer. The physics don’t change. However, I think a pump (or hull) fixed is easier to use for understanding pump internal flow losses. This because those internal flow losses depend on flow speed relative to the pump housing. And for a fully loaded intake and impeller, pump internal flow cares little about how fast the hull is traveling. So choosing a hull fixed system and removing hull speed from the equation seems to make sense and would be my choice.
jer
[ September 28, 2003, 12:10 PM: Message edited by: LVjetboy ]

[miketsouth]

That is good clean thinking Jer, and i follow you and really like and appreciate that you took the time to review my theory.
I selected the picking up the bricks thing because it seemed to fit the properties of the jetpump in a boat. When i first got one i wondered 'im burning all this gas, the HP/WEIGHT says i should go much faster, i get the calculated accelleration from the start but it peters out right quickly. So i wondered. and wondered. I put the circumstances in perspective with the bricks and came up with a plausible start point.
Then, i assumed my start point was valid and started working on solutions. The first solution was to pick up half bricks and throw them faster. It works and applies if you realise the effeciency of the pump goes down as the exit velocity increases (does it really?). A real application seems to be reducing the nozzle size (increasing the pump discharge pressure, lowering the volume, and increasing the discharge velocity) (also reducing somewhat the pump efficiency). This is reported to add top end, at the sacrifice of low end.
I really do think the brick thing is close, but it dont explain everything, that is for sure.
Another thing to consider (as you have been patiently doing) is losses in the pump. At speed the center of the pump sees the water smashing into it while the outside of the pump may be moving somewhat faster than the water. There may be a loss there. Seems intake grates and inlet impeller design do a lot for the jetpump at speeds.
So why would there be a wall if I can simply add more power to up my intake flow speed by the same amount and remove the wall?
Thats the point. You got to do it with a jetpump. It is the puzzling WHY, and then to workout a good solution such that 330hp in a 1200lb boat limits you to 65mph at 2gallons a minute, when your buddies bass boat with 200Hp does 80mph. Yes, you flat jump him out of the hole, but that dont last long. About as long as my gas in the jetboat. Dam.
Like i said Jer, thanks for the conversation.
mikeT

[LVjetboy]

Like you Mike, I've thought a lot about this. Just wish I remembered all that stuff about fluid dynamics and what was it...control bodies? Something like a free body diagram only for fluid forces? Must've killed those cells. Just bits and pieces left :)
Jet pumps accelerate like nothing else but are weak in both efficiency and top speed. Although the top speed thingy may just come from losses. As you hinted in your last paragraph, I think a good approach is to compare pumps to props and ask why are props more efficient? What's different about how they drive the boat forward? Once the sources of loss are known, what can be changed in the design to either reduce or eliminate them?
To me, the dual pump design does nothing to address these losses...may actually magnify them.
jer
[ September 29, 2003, 02:21 AM: Message edited by: LVjetboy ]

[miketsouth]

One of the reasons the jetboat has good hole shot is because maximum HP is available right from the start. Tie one of them bass boats to a dock or a slolum skiier and the rpm is low and the pull is dismal. Jetboat dont care, max rpm right now. Pull your arms out of the sockets.
Another reason for slow holeshot in a prop is the natural tendency of the prop to slip and loose efficiency. That low rpm is further mitigated by the slip.
Jetpumps dont seem to slip. Only a little bypass by the wear ring (that is seen as an efficiency loss, thus the 'ultimate wear ring').
The jetpump picks up the water and throws it out of the back. Might as well be bricks. Water pushes the boat.
Prop boat pushes the water. Prop pushes the river.
And how about them surface piercing drives. They dont seem to have a speed issue.
Most of the prop seems to be always going faster than the water. Look at the angle of attack on a prop as the blades radiate out from the centerline. Angle of attack changes.
Then look at the impeller. Same angle of attack I think :confused: . Hmmm.
Jetpump impeller is going faster than the water at a standstill, but not at speed. LOTS of it going slower than the water. Can this be it?
at any rate, good luck to you Jer
miket

[LVjetboy]

Props both similar and different. Probably the best comparison (for understanding jet drive efficiency loss) is jets and v-drives, as both power-to-weight and weight distribution nearly the same. O/B's get additional speed benefit from light weight engines and that weight far aft...which complicates the issue.
I think you're right about hole shot and prop slip. Our "prop" is both a shrouded design and confined within the pump...that confinement may help keep the impeller loaded. But the shrouded design also takes an efficiency hit at speed. Shroud-to-wear-ring viscous loss and shroud induced flow losses on the interior.
You mentioned a surface piercing drive. I think these work well because the loss in thrust from a partially exposed prop is more than offset by the decrease in drag from raising the lower unit. Just a guess, but if so, another good example of how critical water drag losses are to drive performance.
About the impeller going slower than the water at speed? My first guess would be no. As in you can't force more water into the impeller than the pump can flow. But I'm wondering what speed you refer too? Water flow thru the impeller (or prop) is pretty 3-dimensional, so water velocity has three speed components.
BTW, I have no buddy with an 80 mph bass boat but if I did, imagine the surprise on his face when my inefficient 65 mph jet boat passes his a** doing 90+ I can see it now as we pull side-by-side, that smug grin of his saying ya right, just another slow-a** jet I'll show him. Soon replaced by a look of dismay as my blonde copilot waves goodbye and we leave his efficient but sorry rice burning a** in the spray...
JETS RULE !
Thanks for the wishes of good luck. Hoping for top speed numbers soon.
jer
[ September 29, 2003, 02:28 AM: Message edited by: LVjetboy ]

[pops1]

BEAR_454PE:
I too commend those doing R&D and bring these dual systems to the market at affordable prices for it is through such efforts that new generations of pumps, both single and double, will evolve.
jak I did not single out your comments I just picked you as a entry point.
Lets look at the facts:
SIZE PUMP- A 9 1/8" "AA" (our 9" left, over size in cut) killed rpms from 8200 to 7400 Awesome Toy on his Blown Alcohol Motor.
David Kirklands "Smoking & Stroking" ran a "B" cut version of our 9" impeller (left oversize to a 9 3/8" size). and Ran a 176 or 178 MPH pass.
So untill you get to big for the 9" impeller which can be cut up to 9 1/2" on the large Dia. what is your reason for a bigger pump.
#2 We make a Impeller in the 9" series called Big Mouth- Its a Larger Entry Impeller -(Larger entry flow rate) 30 to 35 were released to Race Boats- It worked on Big HP Only, yet did not justify a need at this time. Above numbers still reflect that motor torque size cannot overcome the 9" base configuration as being used today. Big Mouth sets on the tool rack.
I do not know where you get the side wall drag bit
stated in one of the upper comments. Yes there is Drag as a bottom also has drag. None of this off sets the in-efficient loss of a Prop vs a Jet Impeller. What your statement seems to say is the jet is inefficient which it is not- it is the method of load required to run the jet not the jet.-What I am saying is you will not tail walk a jet- you can tail walk a prop! Again if I am right I take my first love "Outboards for the win in HP to HP top speed" I take the "Jet In "Get There First" So that leaves the V Drive and Outdrive completly out of the game -yet that was my second love.
Again if you put a Impeller vs a Propeller to Thrust Testing, hands down the Impeller wins.
It has to- the water is locked in.
I think a big break thru in Jets- are Tunnels, running with shoe's "up and inside the intake", not down and below, because good builders understand the bubble and how big it must be to make it for the HP to be run. I still see some of the older builders trying the other way (Shovel Intake below the keel line). If I was a Safety Tech. I would not let a jet run with the shoe below the keel line. I know what I am saying will piss off some- Yet that shoe can make a Jet get stupid real quick! Reversion occurs in intakes and causes confusion, leading to barrel rolls, swapends, diggers and a host of unsafe conditions. Any hull design that cannot go straight on a shut down should be junked.
Tomorrow I see non Tunnel Hulls with outriggers as lift is no longer needed with todays HP/Torque outputs(Big 3000 + HP Units). I also see Jet Boats doing well in this class on big HP.& Dual Drives.
Tomorrow I think our Dual Mid Drive will be the kind, based on smaller Impellers and starting with the small blocks on up. What I do expect is more efficiency, due to (output thrust-pull pounds) with quicker & far better fuel efficiency at all RPMs. That is the same kind of data showing up on 9" Duals.
Dual persuit is Thrust persuit. "thats all"
Limits are still the Intake loading. Yet the Performance Builders proved adjustments and changes could occure and overcome. The bubble was as simple as taking a spoon and putting water over one side and then the other- One way it resists and splatters the other it flows.
Some of the your thoughts do not allow for by-product of thrust to pressure as staged in the bowl. The Dan Nelson Blown Boat had A Pedo tube and we found the tube reading was much the same as the MPH @ the nozzle while posting over 500 pounds in the bowl. My thinking for me still holds true as we have seen a consistent 100+ pounds of pressure drop when we change over to our 9 vane bowl vs others. It has out miled and quicker ET'd with this change over also.
Yet the Bowl pressure has been reduced, to my thinking the only way this can happen is it increases the pull load of the Impeller.
This brings up a thought- that I have not looked at Yet, Rob Crunic (hope I spelled it right) @ Eagle Boats told me the bigger the varience between Intake pressure & bowl pressure is speed. Our nine vane both drops Intake & Bowl pressure but what is the net diff. A 100 pound Bowl drop on a 65 pound intake is 6.5 pounds, yet I belive the intake pressure has dropped more than that.
Thank you guys for the mind toggles- good stuff
Dave

[UBFJ #454]

Dave -
I always welcome input from a pro such as yourself that has "Been There, Done That".
In your last post it seems that you attribute some things to me that I did not say ... Actually I don't think I said too much that was really that technically specific ... mainly generalities is all. Perhaps you were addressing others posting here as well as some that I did say.
As far as what I've said, it might help if I clarified a few things.
First, I'm dealing with two problems: 1) Getting the boat we are currently running dialed into the PE & UBFJ classes and; 2) Designing, finding funding and building a true TF jet boat capable of running with the current TFH's. While this project is currently underway, it comes second to #1 and may take another 3 to 5 years before coming to fruition ... it's kind of known amonst our crew as Crazy Jak's Project.
My comments about my thinking that we, for our project, need a larger single pump setup have to do with the TF boat utilizing a very high torgue (@lower rpm), 6,500 to 7,500+ Hp nitro motor ... I was referring to that and that alone.
Our PE/UBFJ boat is a open cockpit, tunnel picklefork with race keel that has its shoe up in the intake, above the keel (for the reasons you pointed out ... and I definately agree with you about shoes below the keel ... crazy, especially with our ticklish hull). Currently we are pulling more than 1,500 Hp (and substantial torque) out of the engine somewhere in the 5,200 to 6,300 rpm range, but, could get upward of 3,000 Hp if we wanted as it was designed and built to go there: Without a capsule boat we are not going to go with any more Hp than we are currently making ... no need to.
As you say, the problem when going fast is keeping the intake loaded ... exactly the problem we're now experiencing. We've only been able to take the boat to two races here at Firebird and have never been able to keep the pump loaded in the second half of the track even though we're now running consistently in the lower 8's. To address this I am currently fabricating a set of very different loaders to try at the World Finals here in October. If that doesn't work, we'll make the decision whether modify the keel slightly and/or try different impellers.
Are you coming to the World Finals? If so, please stop by as I would very much like to meet and talk with you more on the subject of evolving pump design(s).
Jak

[LVjetboy]

Bear, some of Dave's comments were directed to me I think. For those I have a response but for now gotta run! Back Thursday?
jer

[pops1]

BEAR_454PE:
Are you coming to the World Finals? If so, please stop by as I would very much like to meet and talk with you more on the subject of evolving pump design(s).
Jak Forgive me I get rushing -takes time to post, I just go straight to it, no edit. I will be at the World Finals this year. Just got my spot# 58 for the Motor Home at the end of the stands.
Comming with my brother in law-an advid Racer who got two new knee caps that both need "Burnning In". Heck maybe 2 of my Cadalic's we can get in a
Electric Scooter Race with some good whoop's in it or something.
I am impressed by the calls I received & who all are comming. Yankees, Homeland, Rebs, Alamo boys, all are towing and will get to face this wrinkeled As* Prunepicker.
Looking forward to meeting you- Got that CRS (can't remember sh*t)so help me out.
I take all R&D talk as productive & love the discussions and ideas presented both ways.
Understand, I do not put myself in the catagory of you guys that build your motors, set up your rigs & run them. You are a very special breed I love & grew up with. My Step Dad (V.O.Smith) was a Genius who built & operated Belled Casson Drill Rigs in our backyard. The sky would light up untill 9-10 pm as he welded up whatever it was he was brainstorming on.
Lions Drag Strip Long Beach Ca, I think was started in our backyard and I know most every Big Name had his rail over for help or engineering.
I am very blessed to be able to get to be
part of this team. You know
it still comes down in the end to the Racer Builder Guy Who make's it work and work better.
Your the end of the food chain.
The guy next to you holding that rope will eat you shorts.
Later, bring everyone to your camp, to show them the big hole he left you with.
NO MERCY!
Yet he is the same one that will loan you any part he has you need
-just So He Can Do It Again.
-My kind of people!
Looking Forward to meeting you and everyone else
I can. Dave

[pops1]

LVjetboy:
Like you Mike, I've thought a lot about this. Just wish I remembered all that stuff about fluid dynamics and what was it...control bodies? Something like a free body diagram only for fluid forces?
jer I pray god its not as bad as the picture painted by the formula's.
What I do preach is (and maybe some formula will bear this out)Forward pull motion is the
highest % of the impeller. I don't think you will disagree with that.
Most Jets I see Run out of Impeller before finishing- You can see them- they fall off the bubble then climb back on it & fall off it again.
On boards bear out its not load.
Take a look at the 1/8 mile tickets
its all pull and yet the MPH is 85+% of the finish line speed.
I do agree with your somepart of your intake/suction load analysis, yet think you are giving way to much value to its effect. With HP we have persued the flow @ the impeller thru the bowl and came up with 14-16 MPH changes again & again. We then followed this thru the nozzle system and found more. Whats slow is to change minds on set ups and I understand why.
Yet Jets have picked up 20 MPH & cut
.4,.5 & up, off the clock. The 20MPH is not as strong as the E.T number % wise.
To me that number says more than the MPH# by a long shot. Is this telling something!
Please understand I am not relating all this to the Jet- HP Torque are all part of this also, yet the E.T. number holds the biggest interest to me. Z-Food for the Brain-
Dave

[UBFJ #454]

Jer - Hope you can make it down to the World Finals so you, Dave, Mike Sampica (our crewchief & open boat driver) and I can get together and discuss all this in person ... lengthy discussions probably should be in the evening after we're finished racing for the day cause we're all going to be focused on getting the snake dialed in during the day. We are going to be doing T&T on thursday.
Jak

[pops1]

BEAR_454PE:
Jak Blackbear Racing-
Looked at your vidio-The right people
will be at Firebird Raceway.
Youneed to bring some Vidio so it can be
looked at and maybe get some help. Looks
Good- I would like to know more about your
project.-Dave See you there!

[UBFJ #454]

Dave -
Will Do. Will also have the Edlebrock data there.
Look forward to meeting and discussing things with you.
Jak
[ October 01, 2003, 11:55 AM: Message edited by: BEAR_454PE ]

[THE BOSTON SIDEWINDER]

SO WHAT IS MY CHOICE OF UNDER 30 FT HULLS WITH A CUDDY CABIN TO RUN A DUAL PUMP SET-UP AT THIS POINT, AND WHAT BOATS LIKE THIS WILL BE TESTED IN THE FUTURE?...BILL.

[pops1]

THE BOSTON SIDEWINDER:
SO WHAT IS MY CHOICE OF UNDER 30 FT HULLS WITH A CUDDY CABIN TO RUN A DUAL PUMP SET-UP AT THIS POINT, AND WHAT BOATS LIKE THIS WILL BE TESTED IN THE FUTURE?...BILL. Another Drive system is out and on the market now.
We are still testing ours in several
configurations and plan to wrap up by Spring.
We also have designed a pump disconnect system where you can disconnect each pump, should pump failure occure. Do not know if this will be a re-tro or inline release. Also looking at Belt,Hi Voe Chain,or Gear as drive system. All provide over/under drive options wanted.

[pops1]

THE BOSTON SIDEWINDER:
SO WHAT IS MY CHOICE OF UNDER 30 FT HULLS WITH A CUDDY CABIN TO RUN A DUAL PUMP SET-UP AT THIS POINT, AND WHAT BOATS LIKE THIS WILL BE TESTED IN THE FUTURE?...BILL. I think in the long run Dual is your choice.
HP of 600 in a 9" Impeller Drive for your boat.
I am also hoping 350 HP & up on our 7 1/2 to 8" drive. The 9" should give you a Great Runabout type unit in your size.

[pops1]

LVjetboy:
Bear, some of Dave's comments were directed to me I think. For those I have a response but for now gotta run! Back Thursday?
jer I added this for your Info and perhaps this is what you are making referance to.\
The Alcohol Boats seem to be returning to Single Prop as E.T.s Seem to be slower from Drag or Gear
Loss.
Fuel Boats seem to be proceeding forward on Dual Prop as it takes away a lot of the violent reaction found in setting the attitude of the Fuel Boats and providing what seems to be a much safer launch & run.
This may be one of the points you were trying to make.
It sure is interesting and I hope to talk with some of these Guys @ the World Finals.
Dave