Re: Johnson TD20 / TN26 etc. – T-shooting Part 2

[aquasonic]

legendre,

You are correct that there are no crankcase seals, so crankcase sealing relies on those close tolerances and proper use of the correct crankcase sealant.

I went back and read your original thread "Johnson 5hp TD20 ignition timing facts & figures?" and I read a couple of things that got my attention. One was that you saw evidence of someone splitting the crankcase halves with a screwdriver or chisel. I don’t know what kind of damage that could have caused to the mating surfaces.

Another thing was that you sealed up the crankcase with Permatex Ultra Gray. Although I have not used that product, I would question whether it is recommended for non-gasket applications where such tight tolerances are involved. It may have too many fillers, silicone, etc., that could prevent the crankcase halves from achieving the proper tolerances.

When I had questions about what sealant to use, I asked Mumbles, and he recommended Permatex 51531 Anaerobic Flange Sealant.

http://www.ebay.com/itm/Permatex-51531- … ad&vxp=mtr

This is a very thin purple sealant without fillers that is made for this application, and it has worked well for me. Permatex also makes a slightly thicker anaerobic sealant that is better adapted to gearcases and two piece tanks. That is no. 51813, and it is red in color.

Good surface prep and proper torque are very important. I think I am just about out of ideas here, hopefully someone else has an idea that will help.

Brent

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