With the boat on the trailer, I pumped in a lot of water out of a garden hose, crawled under and around and watched. The only place that developed a drip was at the lower rudder attachment fixture. Easy fix: I used flexable non-hardening Red RTV sealer. Hint: after coating the attachment fixture with RTV around the holes, also coat the head of the bolt where the shaft of the bolt meets the head (the part where the wrench or socket goes-on). Tighten the nuts on the inside of the boat, but do not allow the bolt itself to turn what-so-ever. If the bolt turnes, the seal is ruined and you'll have to start all over again! A good soft copper washer would probably be fine on the bolt....the typer of copper washer found on aircooled Volkswagen oil drains (if it'll fit). Another method of repair could be to use a very paper thin rubber washer on the bolts between the hull and the fixture, and the copper washer on the outside of the fixture between the bolt and the fixture. Any thought of using "O" rings wouldn't work. A chamfer would have to be cut into the mounting fixture for the "O" ring to compress into, both on the hull side and the bolt head side of the fixture. In doing that the chrome finish would be lost, and the attachment fixture would rust.