FWIW…..I have an aluminum flat bottom Jonboat that stays on my pond now (had a nice old 9.9 Johnson outboard for it but it got pilfered….another story.) Quite a few years ago I spent some time on it and replaced a number of rivets that had worked loose, painted it and replaced the transom wood with some mahogany that I had from other projects. Used 2 coats of marine grade varnish and it’s held up perfectly. Sits outside 100% of the time. Miss that 9.9 as the combo was the perfect little boat for fishing small rivers and lakes around here. Oh, also used all stainless steel hardware.