Will marine tex work on the exhaust plumbing that feeds the bottom of the manifiolds. I removed the stainless plumbing to have them powdercoated. A couple holes only have 2 or 3threads left. I don't care if they become permanent, because I will just replace the exhaust if I ever need to remove them again. What kind of sealant can I use on the rest of the fittings that have a decent amount of threads left?

If it's only missing threads and the manifolds are not completely ate up. I would take a die grinder with a rotary file, clean all the bad material out have someone tig weld alum back in, drill and re-tap pipe threads.

i think a better product is j b weld.clean the surface good w/carb cleaner and rough the surface up and seal her up.i have had good results.

Would it be possible to drill the hole for the next size larger NPT, and tap it? Then install a new fitting, or a bushing? I dont like the idea of "glueing" it.

+1 Stuff is amazing.

There are a couple threads left on half the hole and the other half has a few more threads than that. So I think it will screw in tight, just might not seal up. So that's why I'm leaning towards just using jb weld or marine tex. Also the manifolds were just powder coated so I don't really want to attempt any welding.

Marine Tex (Big Fan) The gray is stronger than the white Good luck, Greg