Merc Classic 50- cylinder 3 no fire.

[benvan77]

Mercury classic 50. Has gotten a rough idle. Was out on the lake and did not want to acclerate. Got around 8mp- then after a few seconds of rough running, it would climb in rpm and scoot along a 16ft boat at 25mph Then when at lower throttle 60%-idle it would run rough like spark plug was fouled. Got home checked plugs all looked ok, cylinder 3 looked a little dirty. Cleaned reinstalled. Cylinder 3 not firing at all? What should I be looking at to fix this firts?

 

[racerone]

Explain clearly-----Is there no spark on #3 or when you pull the lead off with motor running there is no change in RPM

 

[benvan77]

This is a 2stroke 4cylinder. I pull the lead off of number three no change in rpms. I put my finger in the plug wire, feel nothing. Other plugs from the bottom up, 1,2, 4 I put my finger in the plug wire and outside of getting shocked can hear the spark.

 

[MH Hawker]

Sounds like a bad coil.

 

[benvan77]

anyway I can confirm it is indeed the coil?

 

[racerone]

Test it yourself-----Switch the #2 and the #3 coils and see what happens.

 

[benvan77]

Thanks. Once I do this and if for some reason I still have an issue. Where would I move to next for diagnosis.

 

[Faztbullet]

Replace switchbox........