Spark Plug Question

[eas1007]

Good morning,

Yesterday while putting my outboard to bed for the winter I noticed something strange about the spark plugs. I have a 1978 Mercury 402 (40HP) outboard.

The past 3 years (too busy for boating) it has only been run in the driveway. Mostly while being winterized. I had put new plugs in it back in 2004.

When I removed the lower spark plug to spray fogging oil into the motor, I noticed that the plug was still nice and shiny on the bottom. The top plug was discolored.

I assume that means I am not getting spark to the bottom plug. Correct? The last time I actually used the boat was in 2004. At that time it did not run right. No power, rough running, barely made it back to the dock.

Any suggestions on what I should check next Spring?

Thank you in advance.

Ed

 

[Laddies]

Re: Spark Plug Question

Your right there is a very good chance it's not running on the bottom cyl.

 

[eas1007]

Re: Spark Plug Question

Any suggestion on where to start troubleshooting the problem?

Thank you

Ed

 

[Chris1956]

Re: Spark Plug Question

A lot of times a shiny plug means water infiltration in the bottom cylinder. The plug is actually being "steam cleaned".

 

[Scaaty]

Re: Spark Plug Question

Yep, possible water getting in there (sounds possible here), ...

simply switch the plugs, ground the body to the head, and see if ya get spark on both with the good plug, then check the other