Just find the leaks, loose rivets and such and fix it right the first time. It's an aluminum boat, don't be putting epoxy on it to fix it. You wouldn't screw aluminum patches to a fiberglass boat... well I guess some just might...
Rebuck any loose rivets, look for any cracks and patch with alum and a few more rivets. Sikaflex 1A, or 3M5200 for sealant. You can also go into RONA and buy Sikaflex construction adhesive in gray for about 7 bucks a caulking tube. It's the same, for all intensive purposes, as the 1A.