I need some Help, Im pulling my hair out with this one! i have a 1995 502 MPI, in a Donzi 22, the motor runs fine up until about 60mph but anywhere between 4500 rpms and up the motor just shuts off. It restarts just fine every time and runs smooth until that point. I have replaced just about every part in the ignition system, and yes i have checked fuel pressure which is fine!! I think I need a new ECM, any one have??? Any help would be great!

Have you checked fuel volume and pressure from the mechanical pump? How much cranking does it take to restart after it stalls? Does your tach drop instantly when the stall occurs or does it seem to follow engine rpms down?

Do You Happen To Have The Vst Tank,right Behind The Plenum?they Fill Up With Sediment And Restrict Top End Fuel Volumn.

yes the tack drops down as it is losing ignition, i can start it immediately right up no proplems no excessive cranking,

Also yes i do have the VST tank right behind the plenum, but I have checked fuel pressure many different times and it never drops pressure at all.

Could be the ignition module breaking down at higher rpms, fairly inexpensive to replace.

I replaced it already along with most every other module on the thing, when all fails you just through parts at it right??? Any ideas on how to get a used ECM?

im assuming your johns friend w the donzi . he was going try 1 ecm from his boat but was worried about damaging his in the process . so why not try your ecm in his boat and see if the problem follows .we talked about this i know you cked codes w nothing found . just a sugg and only takes a few minutes

Have you checked the fuel pressure while running the boat when the problem actually happens? At the dock just revving it up won't do it.

I had a similar problem last year and it turned out to be a rich condition combined with fouled plugs. Reached a point where the fire was simply put out at high rpms. As soon as I slowed down, it recovered and I motored on.

Yep, thats that is my next step trying it on his boat, but if It is ****ed will it damage is ****!! I would never live that one down. Also I need to have him check his and see if they are the 5/8 or 1 1/4, i have the 5/8, at this point im about 99% i need to get a new one. Do you have any ideas? are these things rebuildable?