Can you get to the underside of the cleat? If you can I would clean out the whole thing and back up the bottom with several layers of glass. then fill in the top. Finish with gel coat and then re drill for the cleats. I would really back it up alot, long and wide. It may have not just pulled out but really weakened a wide section other than the obvious.
That derelict boat was another dream for somebody else, don't let it be your nightmare and a waste of your life.