My first thought would be "who would ever know?" I mean if you're doing the entirety of the project on your own, it's not like the USCG, fish and game or whomever is going to come up and inspect your boat, ask you to unscrew and pull up the panels on the floorboards to inspect your fuel tank to make sure it's certified or anything. I admittedly have very little knowledge or experience in this category, that being said if you do and you're confident behind your work, I don't see any reason why you wouldn't be able to make it on your own. Again, as mentioned above, I can't imagine anyone is going to ask to see your fuel tanks to prove you purchased it, that it's certified by the USCG and it's not like the boat needs to be surveyed or signed off by anyone before you run it again. My only other thought would be that it likely needs to be pressure tested or something similar, for peace of mind? Again, just my thoughts on the matter of course.
