How do I fix a seep in my sailboat. It has to be fixed from the inside.?

It is down on the area where the keel comes up into. No moving parts involved. It would not possible to go outside and fix it and the leak is washing away anything like 3m 5200 fast drying before it sets. I sold the boat with my house already but the new owner has not taken possession. The leak started a week after he bought it. I still feel responsible but I am not going to pay to haul it out and fix it now.