3800 rpm wall
 

Gentlemen, I am new to this site. I hate to beat a dead horse about an RPM range but I could use some help. I have a 24' 1999 Baja Boss H2X with a 7.4 MPI and a Bravo one drive (don't know ratio because it's not on the drive ANYWHERE) running a 23P prop. Engine starts and runs great, no hesitation, no missing, throttle response is very crisp. We have done a compression test and everything is great. We are currently doing a leakdown test to verify no other problem exists. The issue I am having is the engine RPM will not go over 3800. I have ran a 21P prop and no difference. I have even used the trailer switch while running down the water and raised the prop out until it would throw an 80' rooster tail and the engine RPM never went above 3800. Never did it even try to hit the rev limiter. We have hooked it up to a computer and went for a ride, verified that my tach was reading correctly and it matched the computer to the tee, no codes, no warning buzzers. This has me stumped, and I'm not one for throwing money at something and getting the same results. Do any of you have any suggestions on what this could be?

I would check for a fuel restriction. Verify the pick up tube in the tank is clear, nothing in the anti siphon valve. The best test would be a vacuum gauge connected to a tee fitting placed in the fuel feed line to the engine. You are looking for little to no vacuum.

Is the throttle opening all the way?

I pulled the anti-siphon valve out and it was as clean as a new one. I did not do a suction test though. I will try that. Now if it was fuel restriction would the plugs not show a lean condition or would the ECM correct for that? The plugs look like a perfect running engine.

Throttle buterfly is deff opening all the way with the throttle lever

Have you checked running fuel pressure? Or fuel volume? You could spray "carefully" carb cleaner or brake clean running wide open and see if it changes engine rpm.

Is it maybe in "limp mode"?

Fuel pressure is a little on the low side but stays constant through out the RPM range

According to the computer, everything is within specs while running under a load. No codes are being kicked out and none stored

try cleaning the filter on the hi pressure pump in the VST tank.