Re: Help pinpointing a leak
Hmm! Tightening the keel boats only works if the boat is resting on its keel. Doing it in the water??? Not to be an alarmist but you are getting quite a bit of water with the boat not under any load. Put on the backstay, load up the rig and pound through a few of those nasty LM waves and you might have a much bigger leak than you thought. Best bet is to do it right. Have it hauled and checked. Tighten bolts and really have a good look inside that stringer. Was water trapped in there during the winter and then frozen. The freeze/thaw cycle with entrapped water can can cause fissures in the glass. If the PO had it on a mooring in saltwater it probably never was a problem.
Good luck. My current C&C with the same construction has a bone dry bilge. My previous one had fissures caused by a grounding and a freeze thaw cycle. It leaked constantly and more so when loaded up under sail.