Go to nearest "Welding Supply Store", purchase/order "ALUMABRITE", is a mild etch/acid that is used for brightening aluminum. Is liquid as water, actually, dilute with water and wipe on, watch foam up, wash off, etc. (read directions). Lowe's, Home depot, might carry it. Then spray boat surface with
(can't remember what the name of it is) but, was a very light yellowish coating that permitted the paint to adhear to aluminum.
Check with any buisness that paints aluminum, etc, etc.
Tight lines !
"Teach a man to fish = he can feed himself "
"Teach the world to fish = you won't have any fish left to eat "