I spray mine black a couple times a year with Rustolium.... No Problems.. (trailer boat)

5 years in Salt, I'd think you'll need some sort of Anti-fowling paint.....

Don't Strip all the paint.. Power wash it, scrub it, Clean it.... Then lightly sand it,+ Paint it..... any paint left after your preperation is Good paint, it's doing it's job.. leave it there... Bare metal should be primed with "metal etching primer"(zinc chromate)....