You say you really need a gas tank but some may wish they had yours, without seeing yours or you describing its issues. Is it rusted through or just dented. I’ve never seen an Evinrude tank for sale that didn’t need major repairs. I paid $25.00 for the tank on top for parts to make some of the repairs needed on the tank underneath. The 2nd tank only needed some straightening. There may be a nice straight tank out there for you but expect to pay hundreds of dollars. Tubs
A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.