Well that sucks. What you're looking at there is a pit that has corroded into the aft keel bolt (the one that is commonly under water). I have owned this boat for about five years and I've always manually pumped out the standing water whenever I left the boat. The plan is to haul out and sister in a new bolt (probably bronze) by drilling down from inside the bilge and then in from the side of the keel to intersect the first hole, then chiseling the intersecting hole into a square pocket large enough to get a backing plate and nut on, then after placing the new bolt and hardware in filling and fairing the pocket with thickened epoxy. This method was described by Don Casey in an article in Sail magazine.