I have a 2003 90hp Mercury ELPTO saltwater series that idles rough and tries to stall in forward and reverse at low rpms, which is a HUGE pain when loading/unloading boat. I had the carbs cleaned, spark plugs replaced, and even checked to see if the choke was letting extra fuel in at idle (which I don't believe to be true). I tweaked the carbs to see if it was a rich/lean problem and played with the idle screw. This cleaned it up a small amount, but still not right. It planes with ease still and runs like a top, but when I idle it shakes the boat and even trailer if on land. I took the new spark plugs out after cleaning carbs to check compression (120 all cylinders) and noticed they were already really oily. The cylinder head had oil on it as well.

Also, my spark plugs don't have a gap??!!! They are just flat. Is there an equivelent plug that would be better?

My only thought is that the oil reservoir may be letting in too much oil at low rpms and not at WOT. Only reason i don't at WOT is because there is no oil drip through my exhaust.

Please help I just bought this boat and it's bugging the you know what out of me..........


Thanks

Those are gapless plugs and are the right ones. Make absolutely sure the pilot jets (idle circut) are clean. Edmund.