Our steel (carbon steel?) plates which serve as backing for the washers and nuts which tighten the keel bolts to the hull in the bottom of our bilge are corroded and falling apart. Removing the nuts and washers turned out to be easy but the corroded breaking apart rectangular plates are still firmly adhered to the bottom of the bilge. We don't have enough room to get a big prybar in there plus we don't want to damage the fiberglass. Any ideas on removing them? I don't know how long they have been there or what the adhesive is. Thanks!