I would lightly tap on a good quality 6-point socket over the painted bolts and use a good breaker bar to get a better feel of what/when the bolt breaks loose. Given their location, I can't imagine them being as bad as bolts in the lower unit can be. Doesnt take much effort to break them off, so it they don't break loose easily, a little heat may help. As for protection on the bolts when you reassemble, I'd recommend marine anti seize, stuff I use is made by Jet, and available on Amazon. Don't use automotive anti seize, it has copper in it, and just worsens the electrolysis issue in salt water.