Getting 8,000 RPM from a 15HP power fist engine.

#1
I just finished rebuilding a Bonanza BC1000 and am planning my next project.

I need to achieve 8,000 RPM to power 3 80mm water jet pumps for a powered surf board using my 15HP power fist engine.

I figure I'll need some kind of jackshaft set-up to get to 8K.

I'm looking for input on sprockets to use.
If this is even possible.

Thanks for any help.
 

bruces

Active Member
#2
You wouldn’t need a jackshaft if you can line all the pumps up with the engine output shaft ,your engine probably turns about 3200 rpm at full speed so using something like a 6 inch diameter sprocket on the engine out put and putting somewhere close to a 2.5 Inch sprockets on the pumps (you do the math ,it’s 3 a.m. so I am not ) will get you a theoretical speed of 8000 rpm at the pumps if you have enough torque to turn everything .
 
#3
Good point.
Engine max is 3600RPM
It's a 15HP brand new engine.

I figured with a 25 tooth on the engine and a 9 tooth turning the pumps that should get me to a little over 9700RPM to the pumps.

Does that sound right?
 

bruces

Active Member
#4
Mathematically yes that sounds about right ,but once you add the friction of the water into the mix (like the difference between walking on the beach ,or walking up to your waist in the water )and the friction loss from the chain and sprockets you won’t achieve that speed .Do you know the power requirements of the pumps ?if not what were they designed for originally ?if you can it would be good to know that info ,if not you need to try it out yourself and possibly adjust your sprockets to suit .I guess one of those guys with the pocket protector ,taped up glasses ,and the bottom of their pants 3 inches above their ankle could help you figure out your gearing requirements without the trial and error ,but what’s the fun in that?
 
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