I need to know if I am using the right prop for my application.
I have a 1988 Baja 240 Sport , 454 625hp supercharged motor and I am using a 26in. prop 4 blade. I was out on it this weekend running it and top speed was 69 on GPS, 4500rpm.
Is this in the range for this set up. The motor was refreshed last year. And also there is bottom paint which my be slowing me down a little.
George

You will need to get the wide open throttle RPM up. 4500 is too low for that set up. I would estimate a WOT rpm of 5200-5500 depending on what has been done to the motor. Do you have dyno sheets for the motor?

Dropping down in pitch about 3 inches may get the motor in it's rpm range and also give you more top end speed, reduced stress on your out drive and engine, improved handling, better acceleration and throttle response, etc.

If you have any questions don't hesitate to call.

Matt

Knowing the engines recommended rpm range is critical. It will most definitely be in the 5000's and you need to get it there.

In you propeller testing, definitely give 3 blade propellers a try!

I do have a dyno sheet for the motor. What should I be looking for . And i have a spare prop, it was the prop that came with the boat when I bought it , but I have not tried it since I replaced my motor. It's a 21in three blade,should I try this one? Thanks for the help.

I need to know at what RPM max torque and max HP is produced. Those are two important numbers.

The 21 may be too small but it's still worth trying. Be careful not to over-rev the motor when testing. Take note of how the boat gets on plane, drive trim settings, overall handling, etc.

Matt

Matt, RPM - 5569, HP - 621.4 and torque 566. I'm not to sure about the torque number not to clear. And I am going to try the 21" prop I have.
Thanks for the info.

Looks like you will need to run the motor at about 5400-5600 at WOT. Keep an eye on your tach and gps when testing and let us know what your numbers are with the 21 pitch prop.

Be safe.

Matt

Could this be right, 59mph and 4800 RPM with the 21". The other prop I have is a 27" not 26 as I orginally said.