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Discussion Starter · #1 ·
I have a 1991 155 HP Merc 4 cyl. that starts and runs like a champ but I pulled the spark plugs for the first time today and was surprised to see two of the plugs were oily one more so than the other but still more oily than I was expecting for as well as the engine runs. Could I have a stuck ring or two? I ran Sea Foam through the last two tanks just for Sh**s & grins to be kind to the fuel system and that's all I have done to it since I got it other than today when I performed some PM work. Seems like a real clean / low hour motor. It starts right up and doesn't shake around. I ran it for quite a while last week and it even sits and behaves for quite some time at an idle while a guy fishes without loading up real bad :shrug: What do you guys think? Ron. :cheers:
 

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Put in some new plugs and run er like you stole it for awhile and then check them again if it was stored improperly it could have had the cylinders contaminated with oil leadling thruogh the valves especially on the bottom 2 cylinders ...Don't jump to conclusions without a compression check... Barney
 

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Discussion Starter · #3 ·
Put in some new plugs and run er like you stole it for awhile and then check them again if it was stored improperly it could have had the cylinders contaminated with oil leadling thruogh the valves especially on the bottom 2 cylinders ...Don't jump to conclusions without a compression check... Barney

Thanks Barney! I'll give that a try. It's just too weird that it runs so good :shrug: Bye 4 now, Ron :cheers:
 

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Run some seafoam through it and take it out for a ride like kisser said. Might be a carb issue. I was getting wet plugs, and other issues, a carb kit cleaned it all up.

Good luck
 

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Depending on the hours on the motor its either the carb or possible overfilling of oil ... high hours could constitute a valve tappet adj. but once again a wet and dry compression check will tell you whats going on in them cylinders ...:smile:
 
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