I purchased an aluminum boat a few years ago that had multiple repairs to the bottom with liquid nails. It didn’t leak, but decided to weld it. I tried knocking the liquid nails off with a hammer and chisel, but it didn’t budge. I had to burn that stuff off with a oxy-acetylene torch and wire brush. Underneath I discovered cracks up to 12” long. That stuff is really tough, the boat was previously used to jump over dams in the swamp, and it really held up.