Just picked up a 1990 31' Scarab Excel. Boat has T/454 mags with stainless 23 pitch Mirage props. Both engines max out only at 4000RPM - should be getting around 5000RPM and was told the previous owner had the rev limiters adjusted so they can't go above 4000RPM. Any suggestions on how to adjust these higher?

That is the strangest thing I've heard!!!! 4000 rpm rev limit. Are there any extra non merc components on the engines? If there are limiters, they would have been added and should be noticible. Have to know what you have to begin the process...

What year did they start the thunderbolt V ignition, since it has a rev limiter whereas the IV didn't??? Maybe this is a ThunderboltV and I'm steering you incorrectly...

with motor off . remove flame/ spark arrestor and check for Wide open throttle (push throttle levers all the way forward and check at carb). There also may be a throttle stop on the back side of the throttle levers.

I have the same boat. My motors turn 4400 RPM WOT. I spoke to Julie at Throttle up propellers, she did not find this out of the ordinary. Top speed on mine is 63 MPH on GPS. What MPH are you getting?

bbcngineer

East Coast is right. My 91, 454 mags have no revlimiter (stock). They should spinn about 5000 WOT.
When was the last tune up?

I have a 91 28' XLT with twin 454 mags and it turns right at 4800 with 25 pitch mirage props. No limiter either. I've seen 6000 once (we were inverted).

Have never had the boat tuned up. Just bought it in June. One motor was rebuilt the beginning of this year, the other rebuilt 3 years ago. Both turn the same RPM at WOT. Is there some sort of rev limiter for the prop? I only get about 56mph out of the boat on GPS. I am told it should hit about 70...