what kind of specs for a jet motor

[jshirley78]

I keep hearing "a good car motor wont work for a jet" but, what are the specs or things to look for when building a jet boat motor, either small block or big block. What kind of Rpm range is needed, where should the power be produced. and keep in mind, this is my introduction to jet boats, Ive never owned one (until 2 weeks ago) or driven one and therefore am a little out of my element

[NELSON#109]

figure out what pump you have, what pump you want, what speeds you want, what boat you have, what engine and how much engine you have and want, how much $$$$ you want to spend , and call someone familliar with all of those things and familliar with jet boat cams. call duane at high tech performance marine, he is a smart dude, knows a ton about all of those things, can tell you what cam to use, any other changes you may need, and will help you sort it out. the bigest mistake people make when building an engine is cam selection. car guys know car stuff and the effects they have on engines..... jet guys know jet stuff and the effects they have on engines. NELSON#109

[BrendellaJet]

If you want to go fast, lost the small block idea. Big block. the more cubes the better. Look around for a pump chart and you will get an idea of what the power curve needs to be like. First question is though, how fast can you afford to go?

[*BN*]

Squirtin Thunder's keyboard can push a stump 60mph. :sleeping:

[jshirley78]

I looked at a pump chart and came out being even more confused.... As for what kind of speed I can afford, the biggest lake I have to run is 6 miles end to end with no wake zones every 2 miles or I have the mississippi river which isnt allot better so Im planning on aiming for nothing over 60, prolly spend most of my time around 45

[BrendellaJet]

You need a stock big block. Comp makes a couple of jetboat cams. Build it with a good bottom end. If you're like the rest of us, you'll want more power sooner or later...

[SmokinLowriderSS]

I'm running the same 454 that came in my Tyalor SS. It has been moded a bit, but not much. Same things are 8.5:1 compression, Iron, open chambered, large oval port heads, cast steel crank, cast aluminum pistons, 700CFM Holley Carb, stock oil pump, Aluminum log exhausts, spec'd 330 HP Marvin Miller 150HP Nitrous system.
Orriginal specs: Cam- .480 int/.472 exh hydraulic, cast iron dual plane intalke manifold, Custom made loader from 1979 intake grate & angle iron. spec'd 330 HP. 4850RPM clean, 5200RPM on N2O. Radared 72mph.
Current specs, Cam- .565 lift x 280 deg duration hydraulic, Edelbrock Performer RPM Air Gap manifold, Pro-Loader, Desktop Dyno says 355HP
Spinning Berk A at 4700 RPM, 60MPH GPS'd with a beat-up scarred hull. The N2O untested yet.
Planning on Lightning headers this winter (421HP 465 lbft)
Eventually a head porting (470HP 485lbft)

[Moneypitt]

Cast steel crank??? Cast pistons??...........MP