The centerboard trunk (in the cockpit) of my Mariner has two holes in the top of it - one (the more forward one) has the centerboard cable going down through it but the rear one (which is perfectly round and about 3/4" or so in diameter) is open. What is that one for ? The one with the cable running down through it seems to be not round and has some cuts,etc. in it from the cable. The reason for the questions is related to leaks that I have in the cabin-when rain goes into these two holes I end up with water seeping into the bottom of the cabin floor and I need to find a way to stop them.