Broken Bolts In A Salt Water Engine

[CaptainJim]

I have taken apart a 15 HP 2 cycle engine, and when removing the six bolts for the power head, two of them broke. I spent several days applying PB Blaster, and Screwloose to the two broken bolts.

I went to work on the two bolts, and using vice grips, I was able to remove one of the bolts. The second one is still in there. I am back applying PB Blaster, and Screwloose to the remaining broken bolt. When removing the oil seal housing, I broke off two of the three bolts attaching it. I am also applying PB Blaster, and Screwloose to those broken bolts.

What are the thoughts about applying heat to the bolt or the casting around the bolt?

Being optimistic, when I assemble the engine with all new parts and bolts, should I use never seize on all of the bolts?

[rodbolt17]

typically I use either oxgen/acetylyne or a tap drill and correct size tap or drill and heli coil.
I dont use never seize I use pipe sealent with teflon.