If you search the posts on here, you will see most recommend an aluminum primer as it promotes a chemical reaction that bonds really well with bare aluminum. Having said that, you have to remember paint technology has also changed just within the lsst year. For example, I have a buddy who is a rep for Behr paints, and they have demonstrated to their reps through scientific testing ( ie control paints, large sample size, etc) that their new all in one paint and primer can be used effectively and is very robust on bare metals, including aluminum. They even guarantee it for pai ting bare aluminum siding. The specialty aluminum primers are really effective for harsh conditions where the metal will be exposed to salt and other corrosive salts like potassium. If youre putting your rig in salt or brackish waters, then your primer may flake sooner. If you are putting it in freshwater only, then itll last longer, and if you are not leaving it in water for weeks at a time (ie, docked), then I believe your primer will hold up for a number ofbyears, especially if you use a good topcoat too.