Mercruiser 4.3 LXH Gen+ coil arcing to posts

[bluntinstrument]

So, I have a 1998 Merc i'm at wits end with
It's got 500 hours and always ran great
Recently, I noticed the coil arcing from the bottom of the tower to both posts
I changed the coil first, no change. I then changed the plugs, cap, rotor and wires, all with correct marine parts, and it's still arcing, even with yet another coil swapped in

Typically arcing seems like it would be from extra resistance, but i've addressed everywhere the spark goes

I changed the sensor to the corrosion resistant one 2 years ago

Is there something i'm overlooking? Could something be telling the coil to fire more often than it should? Or is there something causing resistance i'm not seeing? It looks like i've done everything that's solved the issue in similar threads.

All input greatly appreciated!

 

[Bondo]

Typically arcing seems like it would be from extra resistance, but i've addressed everywhere the spark goes

Ayuh,.... Welcome Aboard,...... I completely agree with yer conclusion,.....

1st thought readin' yer post is a bad ground, somewhere, somehow,..??.....

 

[bluntinstrument]

Ayuh,.... Welcome Aboard,...... I completely agree with yer conclusion,.....

1st thought readin' yer post is a bad ground, somewhere, somehow,..??.....

I have the sensor grounded to the riser, should I move it to where the battery cable grounds to the block?

 

[Bondo]

Ayuh,.... Donno's ya gotta change anything,.....

I'd start with removin', Cleanin', 'n reinstallin', with a slather of grease over each one myself,.....
Right from the battery, to the ignition,....

 

[Scott Danforth]

if the coil is arcing from the tower to the two connection points, then I suspect your coil wire isnt seated and you didnt use plug wire grease

 

[Maclin]

Triple check spark plug gaps to be sure they are set to factory. Be sure the coil wire boot is the proper shape for the coil's tower, and does not move around and slide up. Use the dilectric grease on inside of all sparkplug and coil high tension wire boots, dollop some on the coil terminals. If it keeps happening, and you are sure all connections and wires are factory spec are a-ok then look around for a coil with a much taller tower, like msd streetfire or blaster or similar, one that will fit in the location. Also again be sure the coil wire boot fits any new coil, sometimes the coil comes with a boot. Sometimes you need a different coil wire or change the end on what you have to fit a non-stock coil.

Good luck!

 

[bluntinstrument]

So I covered the coil terminals in dielectric grease... no more arcing at the coil!

Now the plug wires are arcing randomly wherever they pass by metal. They're brand new United Marine Mega-Mag, and the plugs are NGK BPR6EFS, gapped to .045

I'm guessing one of the two is the problem, unless there's something else? Could it be running rich and making it hard for the plug to fire?

I was thinking of closing the gap a bit to see if it makes any difference

 

[achris]

...I'm guessing one of the two is the problem, unless there's something else? Could it be running rich and making it hard for the plug to fire?...

Running rich makes it easier to fire. It's lean that is harder to fire...

Those seem to be the right leads, and the plugs are correct, with the correct gap... Check you have the positive and negative of the coil around the right way....

Chris.........

 

[bluntinstrument]

So i'm cautiously optimistic... at the risk of jinxing myself, I replaced the wires with OE Quiksilver wires, gapped to .037 and cleaned off the negative battery terminal. With some wire separators it's looking good - thanks for all the replies. Hopefully this ends the problem! You never know with that baja