Have bought a new generator for our 1988 3218. Logical location is toward the stern on a line between the engines. But, how are the factory installed gennys bolted to the bottom of the boat? There is a raised area here (thicker than immediately adjacent to it) but am unsure how thick it is, so am unsure how long screws can be. Or are factory installs on some sort of platform that are in turn screwed down? Any specific details and/or tricks on install will be appreciated.