Interesting, just assumed it was a steel keel. The bolts are about 6" across from each other which suggests its not steel. The water has been warming up in the river, I'll just dive underneath and take a look and get my trailer measurements at the same time. If it is a faired in lead keel, I guess I don't need to worry to much about the keel bolts. The nuts on top are all but rusted off but the bolts are intact? Still not clear how you extract the bolts to replace them? Do you have to drop the keel? If I put a monster wrench on the bolts, its looks like I would just break them. I wonder if there would be instructions at the Catalina site?