Mercury 7.5 hp sparking sound from coil area?

[Mason Sowell]

Well I got the reverse shift cam put in and carb and fuel pump kits in, runs good mid range to wot, but when you get below mid range it sounds like the plug wire is jump firing to ground, I waited till it got dark out in hopes of seeing the spark. No luck! Just replaced the plug wires (solid core) in hopes that would remedy the spark sound along with the back fire and not idling. Didn't help! It only does it when you go below mid range it starts cutting out, with louder sparking sound. It has new perma gap NGK's in it. Has anyone else experienced this? If so what did you do to solve it? I pulled the coils no visible cracks I repositioned the little ground strap that pinches between coil rubber shock pad and mounting bracket. I'm out of ideas. Whats your thoughts? Thank you once again! 1974 mercury 7.5 hp 2 cycle

 

[water world]

Re: Mercury 7.5 hp sparking sound from coil area?

i KNOW THIS POST HA BEEN HERE FOR A WHILE.. TAKE COVER OFF START DARK IN AREA. SEE IF YOU CAN SEE ANY SPARKING. LOOK AROUND COILS. COULD BE CRACKED. OR COULD BE WIRING. IF YOU HERE SNAPPING NOISE IT HAS TO BE HIGH VOLTAGE...

 

[Texasmark]

Re: Mercury 7.5 hp sparking sound from coil area?

I have had them arc from the high voltage terminal down the side of the bakelike to the ground stud or the 12v stud. This is called surface creep and is caused by a dirty surface between the high voltage and ground. have also seen cracks in the coil bakelike in the same area cause problems.

Remove and inspect and then clean the coil, the wire and rubber boot with alcohol and then coat with silicone grease (Radio shack) to remove the air which forms ozone under high voltage and can cause these kinds of problems.

Other problem could be at the spark plug-cap wire interface or wire-coil terminal interface on the other end....but you just changed wires so the caps and covers should have come with the new wires so that shouldn't be a problem.

HTH,

Mark