Spark Plug Flashover

[brynifer]

I remember reading about this a while ago but cannot find it now. If this is already being discussed, please let me know.
1973 evinrude 135. Over the winter, I gave it a good going over. I replaced the charge coils,they were cracked and leaking,and the sparkplug coils which were cracked. They came with new wires and boots.
When it got a little warmer out, I set the engine up in a barrel of water to run it. I had it running mint, perfect idle. Soon afterward, it started missing. This is when I noticed the flashover. I installed a standard gap plug, L77JC4, this seemed to fix it.
Now the boat is in the water and after having used it a while, the flashover and missing came back worse then ever. I tried cleaning the plugs and boots, coated them with dielectric grease but after a short highspeed run, they still flashover to the point where it won't idle at all. Just to be clear, what I'm calling flashover is arcing from the boot of the plug to the hex base.
I remember someone mentioning replacing the sparkplug boots to fix this problem.
What else might i try to stop the flashover?
Thank You

 

[jonesg]

Re: Spark Plug Flashover

Do you have the correct plug wires?
Did you gap the sparkplugs to 0.30 ?

 

[ondarvr]

Re: Spark Plug Flashover

Change the boots and wires, cheap and easy fix.

 

[brynifer]

Re: Spark Plug Flashover

Well, I had assumed the wires were correct because they came with the coils, but you know what they say about assuming things. I started out with the flush gap plugs that the motor is supposed to have. They gave even more flashover, and yes, i gapped the ones I have now to 30
As far as replacing the wires and boots, is it just a matter of finding good quility, whether it be automotive or marine? Or should I go for original equipment? I believe that the only real requirement is that they be solid core.

 

[ezeke]

Re: Spark Plug Flashover

You might want to try cleaning the grease off the boots with alcohol.

Are the plugs gapped at .030?

The cylinder heads and the rack that holds the ignition coils need the grounding straps to be in good shape and solidly connected.

 

[brynifer]

Re: Spark Plug Flashover

Checking all the ground wires was part of my winter work. I think I fixed the problem though. I cut the boots shorter to expose more of the porcelen ribs. I took the boat for a ride and it ran quite well. I even reinstalled the flush gap plugs and it runs fine with them. It never liked those plugs from day one.
I'll know for sure when I'm able to take a longer run. I'll be looking for better quality wires and boots anyway, but for now I think I'm good.
Thanks guys.