Reading Plugs: A Question for Bob Bourget or other "motorheads"

[Mark Hofman]

I'm almost finished doing my winter maintenance on my outboard. Changed the lower unit gear lube. Put in a new fuel filter. Inspected all my fuel hoses, the bulb, the spark plug wires, etc. Lubricated the trim/tilt rods, the steering and the grease fittings on the motor and trim unit. I've still got to pull the prop and apply a fresh coat of grease to the shaft to keep the prop from sticking on the shaft (and to inspect for hidden fishing line wrapped around the shaft). I also got my new spark plugs installed.



When I pulled the first plug (these are the original plugs that came with the motor), I noticed two things:



First, the electrodes and the insulator had a brown color, which is what they're supposed to look like. The electrodes showed virtually no deterioration. There was also what looked like oil around some of the threads, but not on the insulator or the electrodes.



I'm guessing that the oil is from when I ran a double oil mixture during the break in, or that it's not unusual to have some oil on the threads. Am I right in how I read the plugs?



I also shined a light into the crankcase and saw, on the top of the cylinder, what looked like a buildup of black carbon. I've heard of folks "de-carboning" their motors, but don't know the procedure or product to use to do this.



Would you recommend doing a de-carboning job on an outboard that has less than 100 hours but is at a one-year maintenance interval?

 

[Bruce Freeman]

Thats the nice thing about cars Bob You shut them off clean as you said and then coast around to the pits and apply brakes.....

BF

 

[Staci Matheis]

If it ain't broke..........

 

[Mark Hofman]

So this "Power Tune" stuff...do I just add that to a tank of gas, or is there a specific procedure to follow?

 

[Greg Meyer]

Hey...Boys and Girls... Is that "Power Tune" stuff good for an OMC too?

 

[Jim B]

the power tune gets sprayed into the carbs while the motor is running. there is a procedure to follow and its printed on the can. The stuff does a great job cleaning out the carbon. On my old boat i did it onec a year with the omc version of the same stuff.

 

[Sam Elkins]

For anyone interested below is a web site that has pictures of fouled plugs and what they mean. It also includes surface gap plugs like found on the 90hp mercury.
http://www.gnttype.org/techarea/engine/plugs.html