I dont trust any of them so I plug mine when I am on the water in addition to double clamping them. I hate any kind of through hull fitting that could take on water. I dont like that gurgle sound of water sloshing in and out when a couple of guys are fishing at the stern so unless its raining real hard I just plug em from the outside . The motor well drains I leave open as they ride higher..but if they were lower then I would plug them too..Frank