I have a Merry Fisher 725 (2009). Recently I had an accident where wind knocked the boat from its stands and when it hit the ground it punctured the keel. That revealed other problem, keel was full of water. I suspect that water is coming from bilge, because when I pour water in it, it drains trough the hole in the keel.
In bilge I have three round holes trough stringers. I think that side holes were factory made to tie down the battery, and that the third hole (middle one) was made when additional battery was installed. I think that they moved the batteries to the back of the boat and the hole is drilled to tie both batteries to the boat.
Other option is that the holes are there so that water can move between bilge sections and that they are designed to be there.
Can somebody confirm are there any holes in stringers in bilge between gas tank and motor?