Keel bolt issue
In a previous life I did plumbing and electrical maintenance in a factory. We used to use a product called spraysalvo from chesterton that was nothing short of amazing. You could spray it on a piece of black pipe that was rusted through the bottom and come back in a few hours and it would just fall apart.
I suspect that it would do a pretty good job on those keel bolts if you kept applying it. Might save you some pain.
Back then, they didn''t sell retail, but you might be able to get it through your marina or something. Anyway, i noticed that their still selling the stuff out of an office in Mass. The link is