I can not speak for this brand of self etching primer as I have only recently used it for some bare metal areas on a welded up tailgate project, but the self etching primer is fantastic stuff. Rustoleum is a staple in my paint cabinet however. It should do fine as the only coat on an aluminum boat. It's flat, a color we like, resembling camo, and it really adheres to metals well. DO BE VERY AWARE of it's fumes. It is MORE aggravating to the breather than most paints! It is really meant to have a top coat, but many many boats have been rattle can'd with the cheap stuff with no primer and their owners have been happy. Painting a boat with only this primer would be a step up from regular ole' dollar store spray paint.
