Spark arcing from ignition coil

[timharper89]

1987 4.3 mercruiser s/n 0B459735. Just put as new distributor and rotor and spark plugs in. Had it out on the water today and noticed it was as bit sluggish. Also heard a ticking noise. Then the boat wouldn't stay on plane without being at wot, so I decided to idle it back to the dock. Then it stalled at idle, so I had to keep it about 1200 rpm to keep from stalling. When everyone was off the boat I lifted the engine cover and saw the ignition coil arcing from somewhere under (or through) the boot to the ground screw on the coil. I'm grateful that there weren't enough fumes to cause a disaster. I did not change the wires this year. Is there any reason, other than an old wire, that this would be happening? Figured I'd change the wires, but maybe there is something else to check out. Thanks

 

[Bt Doctur]

either the spark plug is not firing and the voltage has to go somewhere or the coil tower has a crack

 

[achris]

Once a coil starts arcing, it develops a carbon track. Very difficult to stop. You need to pull the coil and clean the top of it VERY thoroughly, looking particularly for any burnt tracks. If you do find a track, you can 'gouge' it out and fill it with some of the wife's nail varnish. Or put a new coil in. Also check the coil end of the high tension lead to the distributor. Look for again, carbon tracking, and that it's tight and clean. Throwing a bit of grease in always help with keeping the angry pixies in the right pipe.

Chris.......

 

[timharper89]

Would this account for the power loss? How do I know which cylinder is not firing? Pull the wires until the arc stops?
​​It definitely happens at a steady, evenly paced interval. Since I just replaced the spark plugs and distributor, I'm going to double check the wires. Seems an odd coincidence that it would JUST start the arcing right when I do that.

What should I use to clean the coil? Parts cleaner? Soap and water? Just a wire brush?

 

[wellcraft-classic210]

Its likely not a coincidence-- The electrons are looking for the path of least resistance.

-- Sort of like lightening does when their is enough energy ( High Voltage) to jump across an air gap--

You probably have 1 or both of these problems ( as AChris mentioned )

1 A bad connection or a defect within your coil wire resulting in high electrical resistance.

2 A carbon track on you coil


Start cleaning with a rag. Them maybe ScotchBrite // Look for a line that could be a carbon track or crack at every step.

If you find one go to Achris's last post for a solution.

Good luck

 

[timharper89]

I'm assuming this gunk is not meant to be there? I ask because the protrusion where the bolt comes out is also black

 

[timharper89]

Looking at new coils, and it seems they are all black up top. Is this part of my problem? The black paint is definitely coming off, and is very gunky in texture.

 

[achris]

That sounds like the coil is leaking oil. Bin it and fit a new one...

 

[timharper89]

Thanks I'll do that.

 

[timharper89]

Would that be the cause of the arcing, or should I expect to see something else wrong?

 

[Bondo]

Would that be the cause of the arcing, or should I expect to see something else wrong?

Ayuh,...... It starts because a component downstream of it is breakin' down, causin' high resistance,.....

Coil wire, Distributor cap, rotor, plug wires, or the spark plugs,.....

As noted, once it starts, the coil's tower is pooched,....

 

[timharper89]

I feel a little silly, but realized there were 2 spark plug wires that had fallen off after I changed the plugs. I could have sworn they were all the way on. That is the obvious dead end for the spark. Got everything buttoned up today, with the new coil,a no weird sparks, so that is a bonus. Got new wires coming in tomorrow. Thanks, everyone.