Crossing from Fort Myers Beach to Key West, the weather says leave this afternoon, pull an over night. All is well until at 4 am we pick something up in the prop and rudder, the boat is shaking, I am in the engine room. We radio Dream Weaver. It takes a while, crab pot? net? Dunno, eventually we are free and carry on. As we approach Key West the alternator burns up, we had symptoms early on but now it is serious. We grab a mooring and shut down the main.