How to Patch an Aluminum Boat

A small aluminum boat takes a beating in transit to the water. It can receive puncture holes because it is manhandled so much. I have built and repaired boats, as a hobby, for more than fifty years and I don’t believe in throwing a boat away. Even a small aluminum boat can be expensive these days. Patch that old boat up and use it for a few more years.

Finding the leak
Put the aluminum boat up on some sturdy blocks in the back yard. Get it high enough so you can see under it. Fill it with about ten inches of water and look under the boat. Mark each leak you see with an odd color crayon. When all the leaks are marked, pull the drain plug in the back of the boat and drain out the water. Turn the boat upside down and mark each hole, plainly, with the crayon.

Preparing punctures and tears for patching
Punctures and tears in an aluminum boat should be closed as much as possible before patching. This will require a helper. The burr from a puncture in the bottom of an aluminum boat will be on the inside of the boat. Have your helper hold a piece of steel on the hole outside while you tap the metal together from under the inside. Aluminum is not hard to tap back into a flat position, so just tap it flat. With the boat still upside down, use a rotary wire brush, in an electric drill and clean a six-inch area around the hole. Be sure to remove all paint and foreign materials down to bare metal.

Patching
Patching your aluminum boat requires fiberglass resin and fiberglass batting that can be found in most auto parts stores. Once the hardener is mixed with the resin, you must work fast because the resin will start to set up and become unworkable. Cut a square of batting to fit the cleaned area around the hole. Mix six tablespoons of resin with one-half teaspoon of hardener, in a throw away container. Paint the mixture onto the cleansed patch area and lay the batting over the applied resin. Paint a coat onto the batting by brushing from the center, outward.

Some of the batting will fray and clump. Remove the clumps and smooth the batting. Allow the patch to dry for about an hour. Mix another small batch of resin and apply another coat. When the patch is dry, turn the aluminum boat right side up and apply the same technique to the inside. When the patch is dry, it can be smoothed out with a rotary wire brush and painted.

Loose rivets
Aluminum boats have keel struts that are riveted to the outside, bottom of the boat. These rivets will loosen at times and cause a leak. Finding the loose rivet on the outside of the aluminum boat is next to impossible because the leaking water will travel along the strut. To find the loose rivet, turn the boat upside down and lay a running hose on it while you’re under the boat. A drip will form around the loose rivet. The leak can be patched from the inside by cleaning the surface around the rivet and applying two to three coats of a fiberglass resin mixture.

Patching a hole in your aluminum boat, using fiberglass resin, can be hazardous. Eye protection and gloves should be worn. Read the warning label on the can before opening it.

Sources: Personal experience