Upper casing threads stripped (in the lower unit end)

[BoatAddicti0n]

I have a Yamaha 70HP 2 stroke, year 1990 (Model/Serial 70BETO -6H3 L 47519 - D)

In the lower unit end, the upper casing (P/N 6H3-45111-10-EK) has 2 out of 5 threaded holes stripped, so that the lower unit is properly fixed to the upper casing only by 3 bolts (1 in the center and 2 in the lft side).

I am assuming it is possible to repair the threads in the upper casing, but also that it is beyond a simple thread repair.

Question
Would be recommended to repair the threads with helicoil or just cut new threads with an oversized tap?

(If not possible to repair the threads due to mechanical requirements, I have an spare engine and could replace the upper case, but seems a bit more work, at a first glace)

Thanks in advance for the feedback!

 

[99yam40]

Re: Upper casing threads stripped (in the lower unit end)

my vote is for the helicoils

 

[robert graham]

Re: Upper casing threads stripped (in the lower unit end)

Since those are some pretty good sized bolts, maybe not enough room/metal to tap for oversized bolts. The Helicoils would be my best guess. They should work fine if installed correctly. I've personally never installed one so would get some instruction/guidance before attempting it. Good Luck!