2 oily plugs, but one shiny clean

[starkyb]

I have my 75 horse Mariner in for service but before I took it in I was running it in the driveway. It wont idle without shutting off or run at full power. I have spark on all 3 wires, just had the carbs rebuilt, new fuel pump and new fuel line. Compression checked out fine on all three cylinders. When I inspected the plugs the #2 plug was shiny clean. The other 2 were dark. What could be going on here?

 

[Moody Blue]

Re: 2 oily plugs, but one shiny clean

Most likely you are getting water into the #2 cyl. The water vaporizes into steam when the plug fires. This steam is what cleans the plug as you described.

 

[starkyb]

Re: 2 oily plugs, but one shiny clean

Is it more than likely the water gasket?

 

[canoemang]

Re: 2 oily plugs, but one shiny clean

More than likely is water intrusion on the cyl with the shiny plug. Im not to familiar with that motor and you don't have year or serial # to verify but it may be the gasket between the plate on your plugs go in and the block.. You'll have to do some searching to verify..

 

[starkyb]

Re: 2 oily plugs, but one shiny clean

it is a 1988 serial # OB262791. Would that cause that cylinder to misfire?

 

[canoemang]

Re: 2 oily plugs, but one shiny clean

it is a 1988 serial # OB262791. Would that cause that cylinder to misfire?

Maybe someone else will chime in who knows more but it sounds like your power head gasket maybe failing letting water sneak into your #2 cylinder.. i am not positive.. but it sounds like it..