Trying to help out a buddy, has twin 454 mpi inboards, one engine will not turn past 3200, other fine, idles fine, runs boat on plane, just stops @3200, no mis or surge. compression about 125 thruout, new plugs, wires, fuel filter, etc any thoughts ? Thanks Rob

Could use a serial number?
I'm guessing it's either picking up a knock and is retarding the timing, or if its a MEFI 3 it might be getting a code 44 and retarding timing.

Look on the side of the block for the knock sensor(s) and see if the wire is connected. Next think make up a code reader and check for codes
[ATTACH=CONFIG]566933[/ATTACH]

have the injectors ever been cleaned?a lot of mpi engines have been damaged due to bad injectors.it could be a bad knock sensor but i would be pulling the injectors and sending them for flow check&cleaning .

Year model and engine serial number so important for any type of advice plus what the set up changes thru serial number runs.

the list .

coil -- cap -- rotor

Possible not running on all cylinders ?

sealed inline spark checkers testing

fuel pressure testing - the numbers are thru out all rpms ?

engine scan ?

Injectors most of the time forgotten about and a lot of the times need servicing regardless.

I would be checking the injectors. My 502 ran fine until a certain RPM and then wouldn't go past. Did new plugs, wires, cap, rotor, filter, scan, and a fuel pressure test. Nothing caught the clogged injector and ended up with a melted piston.

[QUOTE=BUP;4550719]Year model and engine serial number so important for any type of advice plus what the set up changes thru serial number runs.

the list .

coil

BUP really enjoy all of your inputs.

Besides the magic elixir that is used for storage - I've been putting a couple of cans of SeaFoam in the initial fill-up each year (50 gallons)- I use a good midgrade fuel throughout the season - is there something else that we should consider with our injectors -- Oh I have a 454 MPI (year 2000) with about 500 hours - runs just great

thanks in advance

3pointstar

dont have serial # but will have him get it for me, its a 98 engine, removing injectors requires removing top of intake correct ?

The 98 year mfi had bad intake gaskets. Not sure if that could cause this but i have done a few but they all got water in tge oil

serial # OL008645 thanks for all the help...

My 60 hr. Old MPI has 175psi comp., 125 across the board has to be costing some revs. I would think.