spark plugs

[SHLEPROCK]

70 hp merc is slugish and dies some times. While replacing plugs I found the top plug has a yellow tan color and the others were white.
After replacing plugs and running for about 20 hours I pulled the plugs again and the top plug had the same yellow tan color.
I took a compresion reading and all three cylinders were equal.
Do you think this is a carburetor problem?

[SOL]

Bad gas???

[fishingls]

You are most likely getting a different fuel mixture to your top cylinder. This may very well be a carb problem.

[SHLEPROCK]

I hooked a timing light to each coil and the top coil doesn't put out enough to make the light work.
The thing that puzzles me is that the motor didn't seem to have a completely dead cylinder. Could a weak coil put out some spark, but not enough to make a timing light work?

[1pump]

Light tan means normal, white means too lean.
IMHO, the only reliable way to test a coil is by primary and secondary resistance, and even that be spotty. Sometimes they only malfunction when they get warm.

[SHLEPROCK]

When I said white I meant they looked new. :shrug:

I am thinking a cold spark has left the plug stained :whazzup: