I've used JB Weld on an aluminum boat (my buddy's TX17) as a "short term fix". And we applied it from the inside, where the broken or missing rivets were. One hole was plugged with a nut/bolt/JBW, as it was in the bilge area & was slightly bigger than the others. I don't remember how long the plugged holes lasted, but they were eventually TIG welded ( I believe). To the best of my knowledge, the boat is still being fished out of (by the latest owner).