I got tired of constantly sponging water out of my keel stub and so drilled a 5/16" hole through the side of the keel stub at the bottom of sump to drain any water that collects. Water gets into the boat from somewhere and I have to keep monitoring it to keep it dry and free of ice. Now I need to decide what kind of drain plug to put in. I may just epoxy it closed each spring before launce and drill it open again in the fall at haul out. FYI the sidewall of the sump measured about 1 1/4" thick. That's pretty thick and robust for a production boat I would say.