Non conductive silicone

[Dave Hostetter]

I need to add insulation in the mag plate cavity under the coil on a Johnson A35. In 1927, the cavity was filled with a hard tar like material that was removed to put in new spark plug wires. Without new insulation, the coil arcs to the mag plate. Can anyone suggest a non conductive silicone or similar caulk? Thanks

Dave H

[dmbono]

I tucked a piece of rubber roofing sheet under mine.

[crosbyman]

the best would probably be high voltage silicone used to insulate the B+ high voltage coil in TV,s

electronic shops (Radio Shack ?) sell it for insulating the HV coils when the HV coils start to arc or screeech with a a high pitch wistle .

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[kerry]

Would dielectric grease, like used in light sockets, work? Just asking the experts just in case I run into the same situation.

If you have too many, AND not enough, you're a collector.

[vintin]

Anyone here ever used Ambroid cement on arcing coils, etc?

[joecb]

Be very careful about the indiscriminate use of "rubber material" as high voltage insulation. Many compounds of black colored rubber use carbon black as a filler, these compounds will conduct electricity. I found this out after trying to use a piece of black rubber automotive hose as a grommet on a spark plug lead. You can test for some level of conductivity with a normal VOM set on the highest resistance scale.
Joe B

[lotec]

Get all the bits of the tar you took out, heat them up in a metal can and re-pour it back in. If you are careful you can re-use about 80% of it – that stuff lasted 80-90 years, do you really think anything new will do as well? And there is no truth to the reports there are PCBs in there, however, I wouldn’t inhale the fumes.

[Tubs]

A "Boathouse Repair" is one that done without having tools or the skills to do it properly.

• This reply was modified 6 years, 6 months ago by Tubs.
• This reply was modified 4 years, 2 months ago by Tubs.

[cajuncook1]

Please take into consideration, that what ever you use as insulation, must have a certain heat tolerance. The heat of the power head and also the temperature of environment. The combination of the temperature of the power head, heat generated by the ignition, and the temperature of the metal in the summer may cause some insulator material to melt and get real messy. So, investigate the heat tolerances of the what ever you plan to use.

[crosbyman]

there is a special silicone for sealing stove pipes used with pellet stoves.

Since the exhaust of pellet stove is "pressurized" by an exhaust fan you neeed to seal joints with this silicone.

it is heat tolerant and likely a good insulator being clear silicone

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