How to Repair Leaks in Aluminum Boats

Aluminum boats are a staple of the boating industry and is exceedingly durable requiring a minimum of maintenance. They will tolerate being dragged out of lakes on the keel repeatedly and carried on the back of a pickup truck or gently pulled out of the water on a boat trailer. Aluminum boats are found in a variety of sizes and shapes both painted and unpainted. Typically, outside of routine maintenance, the only repair ever needed on an aluminum boat will be to stop a leak if one occurs. Like leaks in a house roof, leaks in aluminum boats can sometimes be hard to find since the location of the water inside isn’t always seen where the water is actually entering. Techniques for finding the site of the leak and methods to fix it will be discussed. The repair tips discussed in this article apply to most aluminum craft but for the sake of simplicity the comments will be specifically directed towards open V bow or flat bow jon boats.

Most leaks in aluminum boats occur at the rivets rather than punctures due to rocks or sharp objects. Rivet leaks are typically not a result of a manufacturing problem but rather due to the rough handling of the boat or impacts with submerged objects such as rocks. While the source of the leak may be hard to find, rivet leaks are typically easier to patch then gashes since usually only one or two rivets will be found to be leaking. Depending on the size of a gash type leak it may be determined that taking the boat to a shop that does aluminum welding is the quickest way to secure a durable lasting repair. A variety of home based approaches may be tried on gash leaks less than 1″ in length.

The first step in repairing an aluminum boat leak is pinpointing the source of the leak. If the boat is convenient to the water it is possible that the location may be spotted by merely placing the boat, with the interior dry, into the water and having several people stationed at the bow, mid ships, and the stern to detect where the water is starting to come in. They should be given directions and indelible markers to precisely mark exactly where the leak is located. If the water is appearing from under an enclosed seat, the seat should be marked with an appropriate note. If the leak is appearing at a seam rather than a specific rivet that should be bracketed and noted. The more accurate the marking the easier the job will become and the less chance for fixing what is thought to be the problem area only to find out it is somewhere else.

If the attempts to locate the leak by this method are inconclusive the next step would be to put the boat on raised supports where there is plenty of open area underneath. This could be a boat trailer or a series of supports such as sawhorses which have been appropriately blocked or padded to keep the boat from tilting on its keel. Once in position the marks made when the boat was in the water can be used as a general guide to filling the boat with water from a hose. Keep in mind that in most cases the leak will be near or at the keel thus do not overfill the boat or it could cause structural problems due to the weight of the water. As a boat owner keep this in mind and use your best judgment on the amount of water you put in since it is beyond the scope of this article to specify what a safe amount to use is. Start with a small amount and work your way up as necessary and as you feel comfortable.

The objective is to have observers with bright lights outside the boat looking for where water may appear. Obviously it is important that the boat bottom be dry when starting this test. It also may help visibility by doing it at night when the user held lights might reflect off tiny amounts of water forming on the bottom. As before, the objective is to determine where the water is first seen and to mark that clearly. Due to the weight of the water in the aluminum boat should anyone lay under the boat. In most cases this test will reveal the source of the leak or at least bracket the location where the leak is occurring.

Once found the location of the leak should be marked both on the outside and the inside of the boat. If you are fortunate the leak will be limited to one or two easily accessible rivets. The more challenging locations are when the leak appears to be under the hollow keel along the bottom center of the hull. The other difficult place is when the leak is under a seat that is riveted in place, especially if it is in the area of the keel where you need to do an inside repair.

Usually the best place to fix a leak is on the outside of the hull since water pressure presses against the patch. A patch inside the hull has to hold back the water. If it seems reasonable you can hedge your bets by patching both the outside and inside at the point of the leak. For a leak along the seam that is hidden beneath the keel on the outside you typically have no choice other than to patch it from the inside. If the leak is under a riveted seat your options are to fix it on the outside of the hull or to saw a access port in the side of the seat nearest where you think the leak is located.

Many procedures are discussed in the literature or online for repairing aluminum hulls. It appears to be generally agreed that fiberglass is not appropriate since it does not flex as the aluminum on the hull does. Aluminum brazing rods, which can be used with a regular propane torch, are also advertised. Feedback on boating forums seems to be divided on how well these work and what expertise is needed to accomplish the repair. I have not used these personally. Other approaches that could also be tried are JB Weld epoxy and applying paint on truck bed liner available in auto parts stores.

One compound that seems widely used is 3M 5200 sealant. The surface of the aluminum and rivet should be cleaned and the sealant is applied much like caulking. It forms a durable patch that should last years. It comes in a regular and fast cure format in 3 ounce and caulking tube sizes. One word of caution is to not buy more then you will use at one time since once opened it will cure in a day or two even if you reseal the tube.

Another approach to repairing a leaking boat is sold by Cabela’s Outfitters and is called Cabela’s Aluminum Boat Patch. It is applied to a clean aluminum surface with the use of a regular propane torch. It can be somewhat inconvenient if the leaking surface has been painted since this will have to be removed with sandpaper or a wire brush. The area is heated with the torch until the stick of solid sealant can be wiped on. It can fix small holes, leaking rivets and cracks. Once the boat is demonstrated to be leak free it is possible to paint over these patches if desired.

A leaking boat is a nuisance and reduces the enjoyment of boating or fishing. Several easy to apply sealing options are available that should provide durable patches when applied properly. Part of the challenge in repairing a boat is to find the exact place where it is leaking and being able to reach it to clean and apply the patch.

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