How to Get a Dent Out of a Boat

by Chris Stevenson
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Aluminum has several advantages over fiberglass, cement and wood when it comes to marine applications. It is light, with very good corrosion and weathering resistant qualities. Aluminum works well when used on small bass boats, dinghies, ski and sailboats and even some yachts. Aluminum typically dents when encountering an object, whereas wood will crush and fiberglass cracks. Removing a dent in an aluminum boat requires techniques very similar to auto repair, since many of the same tools can be used.

Step 1

Put your boat on a trailer and transport it to a suitable work location. Remove the engine: for outboards release the transom clamps, or use a socket to remove an engine from a jack plate. Remove any loose items in the boat, such as stand-alone bench seats, bait boxes and other gear. Have some assistants help you remove the boat from the trailer and flip it over, to rest on three saw horses. If the boat size does not permit removal, clear an area on the inside of the hull in the dent location.

Step 2

Slide underneath the boat. Use a felt pen to mark the perimeter of the dent area. Have your assistant do the same on the outside of the hull. Ignite a propane torch and begin to heat the surface of the dented area. You must be careful and not overheat the aluminum to the melting point. You only need to shrink the aluminum inward, and it will require 400 to 570 degrees Fahrenheit. Use a laser temperature sensing gauge to bring the metal to the correct heat range.

Step 3

Instruct your assistant to hold a hand anvil over the dented area. Use a plastic shot-filled hammer to firmly tap the dent, starting at its deepest point. Tap in a circular motion. Reheat the metal with the torch if it cools. Continue tapping the surface inside the marked area, while your assistant firmly holds the hand anvil against the other side. Tap the area until it appears completely flat. There will be some stretching and distortion in the aluminum, which will be normal.

Step 4

Use a drill for a deeper dent, where the metal has creased. Use a small 1/8-inch drill bit to drill a hole through the center of the crack. This will relieve stress. Heat the metal as you did before, then use the plastic hammer and anvil in the same fashion. Once the metal has flattened, fill in the drill hole with some plastic aluminum compound and let it dry according to directions. Place the boat back on the trailer and reinstall any hardware you removed. Re-clamp or re-bolt the engine to the transom.

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