Made more cuts over the weekend. Transom pretty rotten, as is hull adjacent. Are we sure the exhaust pipe is the main culprit? It's hard to see how water works its way upward through the transom. Also, there is a LOT of water in the starboard hull, considering that the exhaust hole is only under water when on port tack and not moving very fast. I can't find another obvious source other than the chainplate bolt holes, but why would starboard be different from port if that were the case? It's puzzling.