GM 350, Mercruiser MIE 260, the spark coil arcs over to the coil nuts a lot

[sdowney717]

I saw it when finally getting engine running again. Frequent arc overs out the coil top. Also touching it may give you shocks. I wrapped electric tape around the wire and the plastic coil top and it helped a lot, but still may arc over. This engine has thunderbolt ignition, engine is 1984.

Does the spark coil leak the arc or is the coil spark wire gone bad.
Or both?

I told slipmate to try a new wire first, can you buy just a coil spark wire?

 

[Scott06]

Only time ive seen that is when i had the coil wire off the cap was testing spark and didnt have it grounded so coil energy had no where to go. Would look at your cap and rotor as i assume the spark is looking for somewhere to go

also inspect the wire replace as needed but i think u are loosing path to plugs in distributor

 

[sdowney717]

Only time ive seen that is when i had the coil wire off the cap was testing spark and didnt have it grounded so coil energy had no where to go. Would look at your cap and rotor as i assume the spark is looking for somewhere to go

also inspect the wire replace as needed but i think u are loosing path to plugs in distributor

Engine runs smoothly. Maybe the plugs wires have too high resistance, worn out? Engine has new NGK plugs.
The arc over was reduced by 90% after I wrapped electric tape around the coil top many times. I have had cap off and rotor and cap looks good inside. That spark jump is around an inch long down to the nuts, or more. It almost seems like it is arcing from the lower part of the spark wire connection, maybe thru the coil plastic. I have heard of carbon tracking forming in these plastic parts.

 

[Bondo]

Ayuh,...... I'd put a new coil in,....
Then ohm the wires, as you say the rotor, cap, 'n plugs are good,.....

Carbon trackin' is real, replacin' the coil fixes that,.....
Ohmin' the wires might lead to the why,.....