Engine cuts off under load

[dtmoke]

Boat is 2003 22V 5.7 merc with 250 hours.

Last season the engine would cut off sometimes when under a load and higher RPMs. So like surfing or high speed cruising. There was no sputter or stumble first, the engine just straight turned off. Every time it did it there was always a strong gas smell. The boat would always immediately start right up again and act normal. This only happens maybe once an outing. I'm gonna throw some parts at it this spring and see if I can fix it. I plan on ordering new plugs, wires, distributor and cleaning the flame arrestor. Any other suggestions? Maybe check fuel pressure too?

Thanks!

[freeheel4life]

Boat is 2003 22V 5.7 merc with 250 hours.

Last season the engine would cut off sometimes when under a load and higher RPMs. So like surfing or high speed cruising. There was no sputter or stumble first, the engine just straight turned off. Every time it did it there was always a strong gas smell. The boat would always immediately start right up again and act normal. This only happens maybe once an outing. I'm gonna throw some parts at it this spring and see if I can fix it. I plan on ordering new plugs, wires, distributor and cleaning the flame arrestor. Any other suggestions? Maybe check fuel pressure too?

Thanks!

This definitely seems odd. Worth doing an ignition tune up for sure. I'm assuming it's a fuelinjected Merc 350 mag MPI. If you are getting a strong fuel smell then I wouldn't think it's pump related but worth checking. Also worth thoroughly checking for leaks if it's that strong.
I am wondering if there's something like a crank position sensor on its way out or a plug with a bad connection. There's very few sensors that will cause that ECM to decide to just stop the engine, but that is one of them. Otherwise errora trigger a derate. Good luck and keep posting.

[KoolAid]

My first guess would be a bad connection on the kill switch, if it just straight up dies with no stumbling down before it shuts off.

[freeheel4life]

^^good call!!

[dtmoke]

I'm assuming it's a fuel injected Merc 350 mag MPI.

Correct

[dtmoke]

I was kind of leaning toward a rich condition, which is why I wanted to go through the ignition system, check for blockage to the flame arrestor, or maybe a failed fuel pressure regulator. But I think you're right, if that was the case, it would definitely stumble first and then it would be hard to start. I don't have either of those problems so something electrical (ecu or kill switch) is signaling to kill it.

[Jetdriver]

Pop the wires of the kill switch and bypass it. That’ll tell you if that’s the issue but obviously you won’t know until you run it like that. Do the cheap, simple stuff first IMO.

[KoolAid]

Also check the 10 pin connector on the engine/engine harness. Just in case its corroded or its not plugged all the way in. It's the red wire which I believe is pin 6.