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im not expert in fluid dynamics but i would assume different vein patterns and number of veins would affect how efficiently the impeller moves the water and how strong the bowl is. Now whats better or whats worse i have no flippin idea...

Im sure when Tom or some of the others read this thread they will chime in.
 

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Sit N' Spin
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A standard bowl has 8 vanes in it. The way it was explained to me from Dave at Aggressor Jet Drives, the ones with an odd number of vanes (they made a 7 vane, a 9 vane and an 11 vane) were made to reduce harmonic that are present on a standard pump spinning at high RPMs. Between the 7, 9 and 11 vane bowls, I know one flows better than the other but I can't remember which one he told me did. Maybe Pops can chime in here on this?
 

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oldslomobile
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Discussion Starter · #4 ·
I was guessing that it would effect the efficiency of the pump, I'm looking to make my pump work with the motor that I've got, (to the best of its ability) I'd like to see some gain for the amount of money and time I have already put in. Im willing to try any thing once with in reason!!
 

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Sit N' Spin
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I was guessing that it would effect the efficiency of the pump, I'm looking to make my pump work with the motor that I've got, (to the best of its ability) I'd like to see some gain for the amount of money and time I have already put in. Im willing to try any thing once with in reason!!
IMHO, unless it's a race boat spinning higher than 6500 RPM, you won't gain much converting from a regular 8 vane. When you dump it wide open, what kind of RPM are you turning?
 

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Sit N' Spin
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Go Chevy and add more horsepower :D

What is your current top speed?

H2O...he's referring to bowls that have different vane counts. However, yes they do make bowls for bigger impellers as well. But none of this matters for a lake boat application.
 

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oldslomobile
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Discussion Starter · #9 ·
my current top speed is 68.5 ALL DAY LONG:mad::mad::mad: i have hit 73 on choppy water once and 70 in chop other times. Im trying for the 70 mark constant any thing more would be great. No way will i run a chevy thats to easy. Gota beat my self up a little with the olds slowness. It dose matter for lake boats if you are never satisfied and are constantly looking to improve. however it maybe a foolish task. I'll still try if fesable to see a gain.
 

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Sit N' Spin
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my current top speed is 68.5 ALL DAY LONG:mad::mad::mad: i have hit 73 on choppy water once and 70 in chop other times. Im trying for the 70 mark constant any thing more would be great. No way will i run a chevy thats to easy. Gota beat my self up a little with the olds slowness. It dose matter for lake boats if you are never satisfied and are constantly looking to improve. however it maybe a foolish task. I'll still try if fesable to see a gain.
68 @ 4900 is pretty decent actually. Without a shoe or a ride plate my boat's doin' 77 @ 5300 so your numbers are close.

Sounds to me like you need to step the horsepower up a bit, and if you plan to do it on an Olds, plan to bend over ($$$).

In regards to what I meant about "it doesn't matter on a lake boat", you don't absolutely need the racing hardware to go fast. Although if you still have the rock grate in the intake, if you plan to go faster I recommend replacing that with a loader. It won't make you go faster with your current setup, but it will keep the pump loaded once you step the horsepower up and gain some MPH.

Check out the White Lightning loaders at Performance Jet.

http://www.performancejet.com/whitelighteningNEW.htm

What kind of boat is it (make, hull length)?
 

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Sit N' Spin
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The reason for bigger bowls and bigger impellers...

A pump eventually will reach an RPM where it starts to lose efficiency...i.e. the pump is flowing near its max flow capabilities. I believe on Berkeley pumps that starts to happen around 6500 or so RPMs. Bigger bowls and bigger impellers allow for more water to flow at faster pump speeds. The speed at which they're needed requires BIG horsepower (1000hp and up).

Having said that, the horsepower range you're currently running in, you wouldn't see a difference. In order for the bowl to be posing an amount of restriction that would allow a bowl swap to produce an appreciable gain, the pump would have to be pumping a lot more water than it possibly can be at the horsepower range you're running it at. Lots of jets are running in the 80-90mph range with standard 8 vane bowls and I'm pretty sure they've had them in the triple digits as well. So for the cost vs. gain factor, IMHO it would be $$$ better spent elsewhere.

As far as the impeller goes, I'd cut down to an A, but expect to see only a 200 RPM difference from that. When working with a particular motor, more RPM doesn't necessarily mean more speed. If the impeller is sized to a size that allows the engine to overspin the RPM where it makes the most horsepower, you will have a drop in speed even though the RPMs are higher, because less work is being done at the higher RPM than would be done if the impeller size simply stopped the engine from revvng past its peak RPM. However I doubt you'd run into this problem going from an A2 to an A at the RPM you're currently turning.

[email protected] is about right (even better than some of the other boats out there). At this point IMHO more horsepower will be needed to see any kind of appreciable speed increase.
 

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oldslomobile
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Discussion Starter · #13 ·
Understood that the bowls are for higher hp. But like in a torque converter if you change the pitch or number of the fins on the stator or the impeler it has an effect on the stall speed(slipage) hence, my thoughts of this being true in a jet pump would be the same. If you change the stall speed on a car it can make all the difrence in the world on how it preforms, understood also that the imp is probably the easiest and most efective way to see this gain even at a low hp it would have an effect switch to a 7 vane and it could cause a positive gain.
 

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Sit N' Spin
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Understood that the bowls are for higher hp. But like in a torque converter if you change the pitch or number of the fins on the stator or the impeler it has an effect on the stall speed(slipage) hence, my thoughts of this being true in a jet pump would be the same. If you change the stall speed on a car it can make all the difrence in the world on how it preforms, understood also that the imp is probably the easiest and most efective way to see this gain even at a low hp it would have an effect switch to a 7 vane and it could cause a positive gain.
You are correct in that pumps act like a high stall converter. However, jet boats and cars are two different things.

Picture you're in a car with your boat engine in it. The brakes are locked up and the throttle wide open, and the converter only lets the engine spin to 4900.

Now picture your boat at WOT...the pump only lets the engine spin to 4900.

Difference is...the boat moves...the car will not. Yet even though the boat is moving, the engine is seeing the same load as it was in the car at WOT with the car sitting still.

Movement of a jet boat has no effect on the load that the engine sees. You could have the boat running at top speed or tied still to a dock, and the engine/pump will only spin to 4900. As far as the engine and pump are concerned they have no idea that they're moving anything...they're just pumping water. The fact that the boat moves is a byproduct of the pump being mounted to a moveable platform. This is why when you stab the throttle the RPMs INSTANTLY increase without the boat having to accelerate to alow them to increase...because the movement of the boat does not provide the load. The water flowing through the pump is what provides the load. The boat accelerates due to the increase in thrust generated at the higher RPM.

Much like a jet engine, most everything in a jet boat is done through thrust...and thrust:weight ratio is one of the many variables in the MPH equation in jet boats.

As far as changing the number of vanes affecting flow characteristics, etc etc...you'd have to be flowing a much larger amount of water through the pump for it to make any noticeable difference, and that takes much more horsepower than you currently have.
 

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oldslomobile
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24 Posts
Discussion Starter · #15 ·
I cant agree with you more in your complet statement in comparing the boat to a car siting still, it's like letting go of the line lock button or letting off of the break pedal if you are a foot brake racer like I was.


You said "The water flowing through the pump is what provides the load." If you change one part of the equation i.e. the bowl or the imp.the load has to change there for the eficiency must also change. Wether it would change for the better is my question. As you know building power in an olds =$$$$. Ive already done the motor to a sutabile unit for perf./durability it is a solid unit. That is why Im looking at improving the efficiency of the pump to its fullest for the motor. Just cuz I spend all the money in the world on a pump that is desighned for a high HP/rpm boat dosent mean that it is what will work for me. Im sure that you will also agree with me on this.

So I guess what im looking for is are there other pump combos that other people have tried that may show me gains. A good performing pump built to my motor is cheaper and more efective than building more HP with the olds.

I want the total packege as efficient as I can get it. efficency=speed. Lets face it this boat will never be a rocketship.
 

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Sit N' Spin
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I cant agree with you more in your complet statement in comparing the boat to a car siting still, it's like letting go of the line lock button or letting off of the break pedal if you are a foot brake racer like I was.


You said "The water flowing through the pump is what provides the load." If you change one part of the equation i.e. the bowl or the imp.the load has to change there for the eficiency must also change. Wether it would change for the better is my question. As you know building power in an olds =$$$$. Ive already done the motor to a sutabile unit for perf./durability it is a solid unit. That is why Im looking at improving the efficiency of the pump to its fullest for the motor. Just cuz I spend all the money in the world on a pump that is desighned for a high HP/rpm boat dosent mean that it is what will work for me. Im sure that you will also agree with me on this.

So I guess what im looking for is are there other pump combos that other people have tried that may show me gains. A good performing pump built to my motor is cheaper and more efective than building more HP with the olds.

I want the total packege as efficient as I can get it. efficency=speed. Lets face it this boat will never be a rocketship.
I see what you're saying. What I'm trying to say is that an impeller change would benefit you more than a bowl change. The impeller cut governs how much of a load the motor sees at a given RPM (by how much water it moves per RPM)...not the type of bowl you run. So to allow the engine to increase RPM you would use an impeller with a smaller cut. Plus an impeller is much cheaper than a bowl.

And since you have an A2, you can get it machined down to a smaller cut. Since you're in AZ, I'd get ahold of Jack McClure at MPD and have him cut it down for you. Having it turned down to an AB or a B cut will load the motor less and allow it to gain some RPM, which just might get you that constant 70 you're looking for.
 

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Sit N' Spin
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...and with my 454 chevy, i only see 50mph. i sure wouldnt mind seeing 65mph.

bad muchacho, do you occasionally work on pumps? we're both local. :D
What RPM are you turning at WOT? What impeller?
 
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