Jet drive / engine Question
 

Hey guys I have a small Volvo jet drive (4.3 v6) and only reaching 3,900 rpm, but reaching this rpm at ¾ throttle?? From ¾ throttle to full throttle no change in rpm or speed. Could this be the impeller (cut or pitch) or something with the motor. The boat runs fine from idle to ¾ throttle. Bad thing is I bought this boat without a motor and putting it back together so I’m guessing at this point.

need to find out what impeller is in pump and what engine power originally was.

the impeller is a "B" and the motor is a 4.3 225hp Volvo. after looking into it i believe it should have a "C" impeller. not sure if this is my problem but the boat had a "C" impeller from Wellcraft.

is the motor a 225 volvo? or is the motor a 4.3 you put in it? passenger cam, dished pistons, wrong induction. those would all effect the performance.

the motor is a stock (or almost stock) volvo 4.3 225 HP jet. it is the motor Wellcraft put in this scarab back in 97. i purchased the boat as a project, the motor was in a basket or most of it anyway..... everything new now execpt for the block. pistons are 60 over and the intake and carb are edelbrock, everything else is new and at stock specs. i just found the original specs for the impeller and it calls for a "C" cut, i have a "B" cut in the boat. just ordered a "C" impeller. i will let you know how it turns out once i have the impeller.

no doubt the b impeller is holding you back in rpm,the c will work better with 225 hp.

The boat is much quicker to plane with the “C” impeller, however 3,900 rpm is max. it is like a rev limiter will not let it go over 3,900 rpm. The boat runs great up to 3,900 rpm and then it just stays at that rpm.??? Could this be a timing issue, what controls the advance on a 97’ Volvo?

No the impeller is correct you either have an issue with the engine, the tachometer, or still not making enough power. I think the jets mostly came with V8's for a reason. You need torque to turn them.

Wannabe