250 hpdi exhaust tuner cracked 3800 max rpm

[Bob-0]

Got a new powerhead, broke it in. wot missing 300 rpm on top end. they said
wait till 20h check. went offshore first 2.5h no prob. 4400 rpm then it drop to
42 then 38 . will not go over 38 now, checked vst, fuel flow, no codes , ran on seperat tank. checked injectors, spark, compression check hot.#1-115
#2-131 #3-132 #4-132 #5-134 #6-134 . Yamaha says no problem.
Yamaha said check exhaust tuner. Piece missing out of tuner. Can this cause
the motor to hold at 3800rpm?

 

[rodbolt]

Re: 250 hpdi exhaust tuner cracked 3800 max rpm

nope
check medium pressure fuel rail and the high pressure rail at the same time at the PROBLEM RPM.
I have seen tuners mostly missing and the engine still run well.
but I suspect you have popped a piston.
have a leakdown test run on #1.