No spark

[Seanbono]

I have a 1987 Mercury 9.9 and I am not getting spark on only one of the 2 plugs. I know it is not the spark pugs themselves and I know it is not the coil. Could this be the stator if I only get spark in one of the plugs. I'm not sure what it is. Please help thanks

 

[galamb]

The stator on the 9.9 ultimately feeds "both" of the plugs. Likewise, the trigger serves both of the plugs. If either is busted you will get "no spark" at either.

If you are positive the plugs are fine and the coils (which would be my number one suspect - coils of this age develop cracks and fail - have changed dozens of 1980-something coils in the past few years on 6/8/9.9 and 15 horse models), and all the wiring is good, then you have a toasted switch box...

 

[johnnygjr]

Run your engine in the dark, and look for fireworks or ohm out coils with a dvm