86' 90hp 6 cylinder (i6) fouling plugs ???

[Bubbdogg]

Recently purchased an older bass boat equipped with a 1986 Mercury 90hp 6 cylinder & having issues with it fouling plugs everytime I take it out ... get 500-600 yards from the ramp & it starts stalling/missing then the engine dies with no chance of restarting without swapping out all plugs. Motor runs and idles like a fine tuned machine when on the muffs in driveway. Put it in the lake ... get going ... and the day goes south quick. New plug wires no luck ... I've ran the original ngk buhw plug no luck ... then the hotter replacement ngk bu8h no luck, carbs adjusted right, timing is right, compression is right, 50:1 mix ratio. I am literally at my wits end with this motor lol ... any help or suggestions would be greatly appreciated yall !!!

 

[racerone]

Test run with a " known to be good " tank and hose.------And when these engines idle really nice the carburetors are too lean for good acceleration.----Try opening low speed mixture 1/4 turn and try again.----Does spark jump a gap of 3/8" or more on all leads ?------Water pump maintained ?-------Enricher system checked ?-------And I doubt that this is a " plug fouling issue " on this motor.

 

[Chris1956]

Yes, plugs rarely foul if carbs are working properly. Are you sure plugs are wet with fuel, vs water? If fuel on plugs, suspect ignition system. If water on plugs suspect exhaust baffle.