bernm3

I Have A 1998 37 Outerlimits Single Step Stiletto, With 800hps, Speedmaster 5 With 1.34ratio, I Cant Get Over 92mph, I Was Running A 32x18 4-blade And Doing 58mph @ 2800rpm, And A Max Speed Of 92mph @ 5000rpm Due To The Rev Limiter, I Sent Out My Prop And Had Them Set To 34 Pitch And Now I Lost My Low End Speed Now At 3300rpm Im Doing 56mph And Still Same Top Speed Of 92mph, The Boat Did 105mph Before I Repowered It Over The Winter And Added 75hp Per Engine. Any Ideas????

The Menace

Even though you may have more horsepower the all important factor of torque and torque ranges important to boating may have been ignored.

bernm3

Well From The Dyno Sheet @ 3700rpm = 855ft Trq, 4400rpm = 872ft Trq, 4800 Rpm = 856ft Trq, And 5000rpm = 845ft Trq
My Factory Rev Limiter Is Still Being Used Which Is Set At 5000rpm, On The Dyno At 5500rpm = 809 Ft Trq

throttleup

The problem is the rev limiter. If your torque peak is at 4400 you need to turn the motor in the 5400-5600 range. If you look at the dyno sheet you will probably find the peak horsepower in the 5400-5600 range. That's where you need to run the motor at wide open throttle to get top end speed.

It's strange that you lost cruise speed with the pitch increase? Your prop slip is very high, 23% before the pitch increase. I would address the prop slip issue before doing any prop work.

What is your wide open throttle rpm now after the pitch increase?

If anything you need a lower pitch prop to get the rpm up in the power band of the motor. The rev limiter needs to be raised depending on the dyno sheet.

Matt

bernm3

how can i eliminate prop slip?

throttleup

First you will need the dyno sheets and find out where the peak horsepower is produced.

Excessive slip can be caused by many factors including; excessive prop pitch, excessive prop diameter, drive height too high, drive too deep, wrong style of props, improper prop work, hull issues, improper weight balance and more.

All of these need to be looked at and addressed.

Before the motors were rebuilt what was the wide open throttle rpm and speed? What props were on the boat before the motor rebuild?

Matt

bbladesprops

Agreed on most all accounts.

The prop work you had done is very strange and was done incorrectly to have lost that much mid range. If you have the original rev limiter and you added HP and added pitch, you should still be able to hit the 100mph mark at whatever rpm you hit it at before.