Use the
electric cables for the
winch to heat the SS bolts. Put the positive side to the
head of the bolt and ground the negative to the nearest metal of the
winch. The leads will act like an
arc welder generating a bunch of heat directly on the bolt. Heat, saturate with penetrating oil, and repeat as often as necessary to break the
boats free. May take multiple applications over many days but should free up the bolts.
Used this trick via jumper
cables to remove all the fasteners from my 40+ year old
mast. Before someone turned me on to the trick, was having near zero luck removing the fasteners. 100% success using it