Heli coil in impeller housing? (pre-Alpha mercruiser 120)

[kd6nem]

Changing the impeller in my dad-in-law's Mercruiser 120 was going too well. As I was putting the impeller cover on, I noticed the one bolt in the back of the cover would never snug up. Now I know why part of the gasket was missing before and why it ran warm at lower RPM's. Now what? Will a helicoil be happy in there, or will it eventually see rust problems or something? I need an insert that will stay put and not have problems being dissimilar metal. I expect I'll lock it in with Loctite Red formula and use anti-seize on the bolt. Sound reasonable?

[achris]

BP,Heli-coils are stainless and it will corrode into the ali housing (eventually), but that would be a good thing. The bolt is also stainless so it wouldn't seize in. If you have the 'meat' in the housing to put a heli-coil, go for it.....Chris............

[Scaaty]

"I'll lock it in with Loctite Red formula and use anti-seize on the bolt. Sound reasonable?"I was a Machinist for 21 years, and thats what I would do. I just did the same to the prop zinc on my VP outdrive that broke and had to drill out. Didn't use any Locktite or anti-seize though as that needs to make a good "current" contact to work. But you can use it in your app.........

[kd6nem]

Thanks, guys!

[imported_Mike_M2]

The bolt in the back has a sheet metal looking thread to it, i doubt they even make a helicoil for it. What i did once was cut a little piece of wire tie and shoved it in the hole. The extra space of the plastic was enough to get it to tighten.

[rodbolt]

the easy way to fix that is to replace the water pump base. the aft sheetmetal looking screw screws into the plastic water pump base. if that is not acceptable then use a few strands of copper wire in the hole to act as a filler. good luck and keep posting

[kd6nem]

Uh, this bolt is a skinny one, takes a 7/16 socket (not sure about actual bolt diameter at the moment), and about 4" long. This one has SAE threads and goes through the base into aluminum underneath. I'm still looking at using a helicoil when I next get down there. I guess there were more than a few variations, which explains why I had so many o-rings left over, since this kit I used covered a wide variety of earlier units. Evidently not quite the same exact kind you fellas have seen. But I appreciate the help, just the same!!!