4.3 EFI cutting of randomly

[BoatService]

Hello.
I have a curious problem with my motor. The engine can run absolutely fine for an hour, and the start to lose a bit of power. Rpms drop a few hundred and if I increase throttle at this time the boat falls down of plane. Turning the engine off for 10 sec and restarting fixes the issue. Up on plane again - may run fine for an hour, or repeats problem within a few minutes. This happened on/off last season. Changed distributor cap and put in new wires and plugs - no difference.
This season the issue seems to have gotten worse. After running the engine for an hour, a few relatively load knocking sounds came from the engine room and the engine cut down completely. Re-stared engine and everything was fine. Drove for another hour - no problems.
Yesterday the knocking reappeared and the engine cut off again. Re-started, up on plane - cut off. Re-started, up on plane - cut off. Limped homewards at 6 knots. When nearly home pushed the engine a bit more - up on plane everything ok, then 3500 revs - no problem.

Thoughts?

 

[o2batsea]

What made you suspect the distributor cap and rotor, plugs and wires if the engine was running "absolutely fine"?

 

[BoatService]

I assumed one of 2 options, either electrics or fuel.
The thought was misfire at one cylinder possibly through damaged wire?

 

[BoatService]

Hello.
Discovered this piece of silicone (?) stuck to the end of the fuelpipe inside the fueltank. I think problem solved.