A friend of mine has a 2000 cruiser with 454 mpi engines. He just recently had a problem where both engines will not rev over 3000 under load. Both engines draw off their own separate tanks. I'm am trying to find something that both engines have in common that would prevent them from operating over 3000 rpm. Fuel systems are separate, There have been no recent repairs to the engines other than a distributor pickup sensor in one of the engines. What other systems do the engines share that would cause them to go into what seems like a safeguard shutdown situation? I was thinking electrical/ alternators. Does anybody else have some suggestions?

Need to hook a scanner to it and if has any codes, they started doing this at the same time ?

Thinking electrical too. If no obvious codes, maybe a shorted diode in one of the alternators causing elec noise on the DC buss. Bad capacitor on alternator output? Could try disconnecting 1 alt output and go for a run. Make sure removed wire is taped-up real good and secured with ty-wrap or something similar. If alt has its own belt, then just remove belt, but I'm assuming it has a serpentine belt.

System voltage too low?

I would check DC supply voltage with a scope if possible to verify clean power to ECMs.

Bad gas??

Does this boat stay in the water? When was the last time bottom was cleaned? What size boat?

Chris

how old is the gas