Few things will ruin your day on the water as fast as seeing your boat spring a leak and water seep in through the hull. All the bailing you will have to do in order to get back to shore could have been saved if you had sealed the cracks or holes in your wooden boat's hull. A few tips on how to seal your boat can save you from an open-water panic situation and get you back to enjoying the boating life.
Locate any spots on the hull where water may be leaking in and circle them with a marking pen. If the leak is not easy to find then a simple way to find it is to completely dry the hull and then lightly dust with chalk or flour. The leak will reveal itself in the dust.
Remove the boat from the water. Ideally you would put the boat up on blocks so that you can work underneath it. Let the boat dry for several days.
Locate the areas on the hull that are leaking. If the leak is in the seam between two boards then remove any loose caulk or wood and fill with silicone caulk. If the leak is in the middle of a board and small (less than 1/2 inch), then drill a hole through the leak and fill it with wood filler. Use a drill bigger than the leak in order to drill out the weak spot of the wood. If the hole is between 1/2 inch and an inch, use a large drill bit to drill out the hole, and then fill it in with a wood plug and wood filler. If the leak is bigger than this, you will need to replace the board(s).
Scrape the entire hull, inside and out, with a paint scraper. You want to remove any loose particles of paint or wood. Sand any rough spots. If you discover any dents, deep scrapes, or large cracks, fill these in with wood filler.
Paint the inside and outside hull of the boat with the marine grade primer. Allow to dry at least 24 hours. Paint at least one coat of marine grade paint over the primer. Allow to dry for at least 24 hours.