Thanks, My local guy diagnosed it and then I recently sent the MEFI to Eddie Young at Performance Marine. Eddie rebuilt my engine and tuned it so we will see what he says. If it has to be replaced that could be tough as Eddie said that my particular model is difficult to come by.

Padraig

A few seasons ago I repowered my 2000 Ski Nautique with a 5.7 MPI from Michigan Motorz the motor seems to be doing well itself, I wish I could say the same for the ECM, I am about to be on my third one. There was no problems with the ECM with the prior motor, the motor was a like for like swap, none of the electronics were replaced. I know this could be purely coincidental with the motor swap, but shortly after that, is when this started happening. I have looked thought most of the wiring around and near the ECM, checked all grounds etc, everything seems to be in normal condition, aside from ripping out the entire wiring harness I am out of places to look. No abnormal events happening before ECMs are quitting, runs great for about 3/4 of a season, then all of a sudden I lose the ECM call for the fuel pump, and then usually no spark after that.

First two ECMs were purchased from and programmed by obd2allinone dot com
Only place I could find that still deals with these old ECMs

I would like to find the underlying problem, but not sure where to start.

If all else fails are there any replacements for the MEFI-3 that are reasonably plug and play with a tune and conversion harness?

Hoping someone with more experience with these can point me in the right direction.

Thanks

If not wiring issues maybe alternator issues.

I havent used one yet but there is supposed to be a AEM jumper harness and ECM that will plug into a mefi, at least a mefi4 which means if needed your mefi harness could be repinned to a 4 to plug in the adapter and work IF they dont make a 3 adapter. BUT as far as a proper "tune " pre-populated for you 5.7 ski boat, no, YOU or your tuner would have to decided WHAT safe timing (vs octane), fuel afr targets etc you wanted and adjust ae, idle, midrange, wot, etc until it ran at least as good as stock, Smitty