Help gearheads!!!
 

I just bought my '91 290 performance with twin 468s, they have merlin heads, crane roller cam and rockers, steel cranks, trw blower pistons, b&m 250 superchargers, and 850 holley double pumpers. Not sure abt the size of the chambers in the heads or the cam duration, but Im working on getting that info. It has Bravo 1 drives 150 to 1 ratio and 15.25 x 26 pitch 4 blade Bravo 1 props. My question is what is the most rpms I can run on the motors, and do you guys think it is propped right?

If you have dyno sheets you can take the RPM where it made the most torque and add 1500 RPM to that and you have what is usually a good WOT RPM range. For example if max torque was 4300 RPM + 1500 RPM = 5800 WOT

I would think that a number around 5500 just be good for your application.

You may want to post this on the Q & A section so all the major gearheads on the board will see it and respond.

Doc

We need more information to answer this question.

1) What is max RPM now?
2) What is your top speed?
3) Does the boat come on plan quick?
4) What is your cruise speed around 3500 RPM?
5) How is the mid range accelleration?

The drives are going to be deep on that
vintage of boat and with 4 blades,
there going to be very hooked up.

And being that they're supercharged,
they're probably propping it
to get the engine to spin at least
5500 rpms. ( hence the smaller than
usual pitch, compared to something
that only turns 5000 rpm)

Judging on what info was given on the engines,
I would say they're probably close to being right,
prop wise

Thanks for the info! I am getting a gps this week to get a true indication of speed. When I test drove it, his gps(portable that he kept) was showing 80mph at 4900 to 5000 rpm, I just wasn't sure how high I could rev em without damage. My old boat had smallblocks in it. It planes out relatively quick, mid range accel is amazing, she's a beast!!!