Repair your aluminum boat instead of replacing it as they are a costly item. Aluminum boats luckily are pretty sturdy boats that rarely leak from gashes but tend to start leaking around rivets and seams. If you have a leaking aluminum boat, then follow the instructions below to learn how you can repair it yourself.
Place the boat in the water and mark with a marker where the water is leaking into the boat. It is important to do this so you know exactly where the repairs to the boat need to be made. It may help to have a couple of other people help you with this step.
Put the boat up on supports and slowly fill the boat with water to determine the location of the leak(s) if the previous method didn't work. Be careful not the ruin the structure of the boat by overfilling it; use extreme caution if anyone is beneath the boat as an aluminum boat filled with water will be rather heavy.
Patch the leak from the outside whenever possible so the pressure of the water actually works with the patch rather than against it. For leaks that are along a seam that is below the keel of the outside of the boat, you will generally have to repair that leak from the inside of the boat. Leaks that are beneath a riveted seat will require you to repair it on the outside of the hull or to saw access in the side of the seat nearest to where you think the leak is.
Clean the area where the patch is to be applied thoroughly.
Apply 3M 5200 sealant to the area to be patched much like you would apply caulking, make sure that you follow any instructions that come with this sealant or any other sealant that you may choose to try. This patch should last for years.