I have an '85, and did the mast compression block replacement myself. If I had to do it over, I would pay large sums of $$ to have someone else do it. An awful project. BUT, that doesn't seem to be the issue here. As someone else has noted, Catalina stopped using wood as the material for the compression block. So, even if water has intruded, the block should be fine. Since there is no compression visible on the deck, and the head door opens and closes just fine, I'd look for another cause. The most likely one has been mentioned -- water seeping down from the mast step, along the electrical lines. This can be EASILY repaired. When the mast is unstepped, you will find a PVC pipe that goes through the deck, with the electrical connections routed through it. Two things need to be done. The opening in the pipe needs to be sealed up so that only the wires extend through, with no additional open space. Once this is done, you will have closed off one of the routes by which water intrudes. The next step is equally important, and often overlooked. Make certain the PVC pipe is thoroughly sealed to the deck, using a flexible polyurethane sealant. In addition, fill in the mast step with sealant, tapering it to the sides of the pipe. If you do not have water exit holes at the bottom of the mast, drill a couple of small ones. If these steps aren't done, any water that enters the mast will sit at the bottom of the mast, and will eventually find some small opening, allowing it to enter the compression post.