I'm at work and trying to figure out the drain plug size for my boat. The guy who winterized my boat seems to have misplaced it and I've tried a 7/8" (just too big) and a 5/8" (way too small). Anyone have any idea of what size I need??? I'm guessing 3/4", but I'm tired of running the the marine shop that knows absolutely nothing about Reinells. Please help...