Merc 5.7EFI Issues

[Chris-380]

Went today to look at the old block and head. Big hole between 4&6, he wasn’t kidding about pencil sized.

The question now is what the hell caused this. He suggested we drain the rest of the tank (30 gallons) and start with fresh fuel.

The manifolds and risers are only a couple years old and there are no signs of any water leakage causing it.

Something wonky in the ignition system causing pre-detonation?

I hadn’t changed the fuel filters yet, lean condition?

How many hours were on it?
We have 5 (including me) that had this happen to 350’s on my 16 person dock. All either 3-5 or 4-6

Basically all that had them for a few years had it happen. Went between 350 and 500 hours.

 

[Strecker25]

749 hours. A little concerning for the other motor, I'm doing distributor, coil, plugs, wires, cap, and rotor. It's due for them and I found a full kit for $350 so good insurance I guess.

Did you have issues after the rebuilds?