Firing on One Cylinder

[coolphil]

1985 Mercury 25 HP, First it just quit running, I check the fire and it had a very weak fire. Replaced the Stator and it ran good for about an hour and quit again. checked the fire again and it is only firing on one cylinder. It is a good fire but just on one. There are two wires coming from the Stator. When checking the voltage from the wires I had about 120 volts AC on one wire and about 10 on the other. That is to ground. Not sure if that is the right way to do it. Is this the way I check the Stator and trigger?

 

[coolphil]

Forgot to say, Its not the coil. I checked that.

 

[67ghiaTIV]

Not a mechanic but trying to help. I just went through a similar problem on my 1988 Merc 20hp. With plugs removed check spark. Then swap the sparkplugs and check again, then swap coil power wires between coils and check again. Did the spark stay on the same cylinder or move to the other cylinder. How do you plug wires look? Any wear or cracks? Check, clean and lightly sand and di-electric grease all connections and check to make sure wires are not shorting or grounding. At this point I knew everything back to the switchbox was good and working so I replaced the expensive switchbox and my motor is running well.