93 250 v76 degree "Advice Please" - fouling or computer problem?

[rooster]

My 93 250 had a new power head put on last year. It worked great all season. This year it acts as if it is missing a cylinder. My mechanic replaced all of the coils and it ran great, once. The next time it began to act up again. We cannot seem to diagnose the problem. Could the engine be running too rich and wet-fouling the plugs or is this a more extensive problem and I should be looking at a possible computer replacement??

[boats.net]

You can look at spark plugs to see if running rich. You will need to find which cylinder is missing and troubleshoot from there.

[rooster]

I changed the plugs yesterday and ran the boat. Same problem. The plugs that I changed were wet with fuel. I imagine that the engine is wet-fouling the plugs.