How to Repair an Old Wood Hull Leak

Visually inspect the leak. A leak appearing at a seam between two planks may be a caulking failure. Stick the point of a jackknife into the wood around the seam to determine whether or not the wood is soft. If the jackknife test reveals no soft wood, place a tube of polyurethane caulk in a caulking gun. Fill the seam with polyurethane caulk on both the inside and outside of the hull.

Remove the nails from any soft planks at the site of the leak, using nail pullers. Strip the caulking from the edges of the planks that remain in place. Sand the edges of the planks adjacent to the hole with 36-grit sandpaper.

Measure the old plank with a measuring tape. Cut replacement boards to the length of the old boards using a circular saw. Position the new board on the boat's rib nearest the end of the board. Dip new marine brass nails -- the same size as those you removed -- in adhesive marine caulk. Drive the nails through the plank and into the boat's rib using a wooden mallet.

Push the plank onto each successive rib and nail it into place. When you finally push the plank onto the final structural element across which it passes, nail it in place.

Apply a bead of polyurethane caulk with a caulking gun between the boards, both inside the hull and outside.