The intake cover also handles exhaust on the “T” series Johnsons. The solid threaded inserts are good, but the ones I’ve seen are larger in diameter than the Helicoil insert. You may not have enough thickness at the mating surface on the motor side. The 10/24 Helicoil definitely works, but even that doesn’t have much extra room. I recall using 1 or 2 on a TD-20 intake/exhaust cover successfully. Use the exact size cobalt drill that the kit recommends.
For sealing/locking in the threads, red loktite works well. Make sure that the Helicoil threads are slightly below flush on the drilled hole so as not to interfere with the screw installation. Don’t over sink the Helicoil either. They are not designed to back out. Take your time, and check as you go. Once installed, don’t forget to break off the tang as per the instructions.
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