I had an old Starcraft 21 footer that leaked. After pulling the floorboards, I filled her up with some water. Water was weeping from many places. I chiseled off the old rivets, picked up new larger rivets. I drilled out the old holes to fit the new rivets. I made a piece of steel up with a hole drilled in it to receive the tail of the rivet.With a helper we pounded the aluminum to tighten up the rivet so it would not spin in its hole. Then we peened it over. I thought I would replace 12 rivets but when we were done, it was 268 rivets replaced. The boat was tight again but a couple years later the transom brace cracked and my outboard was flopping around. I gave up on the boat.
I bought a Lund, it was fine for 18 years but rivets leaked where the trailers roller bolt cracked and the hull had a dent. I now have a Crestliner welded aluminum hull, no rivets.