Engine running rough.... Here we go again !

[bigdog]

Engine running rough.... Here we go again !

Had same issue last year, and think it may be related to ethanol gas.

Have a full tank of gas, leftover from last Fall and winterization. Treated gas will Stabill, back in late Fall as usual (the red stuff). Also fogged engine as usual.

Had boat out twice this season, only for short trips, and had no problems.
Actually, the engine was running 'great', full throttle wide-open !
I think I may have violated the 45MPH rule !

Yesterday, took boat out on water for about 30 min, stopped, anchored took a swim. Heading back to the dock, engine started running rough, and had to pull back on throttle to about 10MPH. Seemed to want to stall as I gave it more throttle. Got back to dock, w/o stalling or backfiring.

Last season had similiar issue, here's the steps I took:
- First thing added a can of 'Sea Foam'
- Checked pickup valve in tank
- Checked Anti-Syphon valve in tank
- Changed spark plugs
- Checked all spark-plug wires
(tested in the cover of darkness also for arcing)
- Changed Fuel filter (thought water in fuel?)
- Drained almost entire tank of gas (that was fun.. NOT ! )
then added fresh gas.

Problem seemed to come and go during operation of engine, but never really seem to totally go away?

Suggestions or thoughts on what the issue may be? Getting frustrated !

Thanks,
BD