Broken stud-block damage

I've removed 6 broken studs out of my Suzuki DT85 exhaust cover with my drill and carbide dremel. All fixed with helicoils. One of the broken studs had a lot of corrosion around it and the seal face on the water jacket side of the power head casting has gone away. The motor is up and running but I had to use high temp RTV silicone to keep the bolt hole from squirting water out through the exhaust cover. I imagine this will eventually require having the sealing face on the block welded up. BIG QUESTION. Can this be done on the powerhead while it is still on the boat? If not, and I have to remove the sucker (powerhead) again, can it be done without disassembling the case? I really don't want to crack this engine if I don't have to. Any welders out there?

Re: Broken stud-block damage

i would try jb weld, if at all possible.