Plug Wire Shock

[MotorlessCSJ16]

I have a 1998 Mercury 25 hp 2 stroke and it has been idling rough for quite a while. Top end seems okay.

When running some fresh fuel through it on the hose today I decided to investigate. Pulled out the bottom plug wire and the motor shut off. Put it back on, restarted, and went to pull the top plug wire and it shocked me. Used an insulator and pulled the top plug wire and the motor ran fine. Bad plug wire? What do you all think?

Also, if it has been doing this for a while, which I imagine it has, could this have caused any serious damage?

 

[mikeneal]

Re: Plug Wire Shock

IMO, anytime the plug wire insulation is bad enough to shock you it needs replaced.

 

[WrenchHead]

Re: Plug Wire Shock

If I understand, you are running smooth at high speed but rough on idle, you pull one plug wire off the plug and the engine idle doesn't change but you receive a shock. Sounds to me like one plug is not firing for some reason. The reason could be the plug wire, the plug gap, carboned up plug or just a bad plug. I would change both plugs and both wires. Also check the cylinder compression when you have the plugs out. Remember to ground the plug wires so you don't get bit during the compression test!

If it's just a bad plug or wire your motor probably hasn't been damaged.

Good luck!