Cleaning painted aluminum hull

So the PO painted the hull with some kind of black paint, and used it mainly in the ocean. It has whit I think is salt on the bottom. Just wondering how I should clean this off on

If it were just salt, it would dissolve with water. Any chance that those are small barnacles? If so, lots of scraping in your future.

and, if that is spray on bed liner, If so, lots of scraping in your future.

You both say lots of scraping. But one because they may be small barnacle other says because bed liner.

I don't think they are small barnacles but I could be wrong.

Not sure if it is spray on bed liner or not, and if it was why would I scrape it all off?

salt washes off just like it would wash off your hands.
it is extremely hard to tell from the photos of what is
actually going on..... just start washing with a degreaser
and brush - progress to more aggressive measures until
you understand what is going on.
Do a vinegar wash in a test spot to see if the spots go away.
If they do, then it is surface corrosion which can be dealt with.
Many members here just don't like bed liner on their hulls.
Matter of choice - your boat - your call

marine growth such as clams, oysters, barnacles, etc mostly
just die and drop off after coming out of the salt water.
If they stick, they are easily scraped off with a blade of some sort.

Shucks, those barnacles on my sailboats cost many hundreds of dollars,, to be scraped off.

ok, and if it is oxidation, how is that dealt with?

i really do not think they are barnacles, but who knows

try the search feature - CORROSION

and, IF that is spray on bed liner, the corrosion is more than likely
trapped under it . . . thus, it must come off to properly treat the metal.
prime and paint.

or, slap some more bed liner on it and sell it quick.

so i just went and checked out the boat a bit and tried what i could. First i tried just a shop rag with water, and then a shop rag with vinegar. nothing.
I then tried a rough sponge with water, and nothing.
Next was the vinegar, well the vinegar and sponge started to remove the black coating/paint or whatever it is from the hull. So i tried just regular water and some simple green with some more elbow grease, same results.
Now upon further inspection i believe the white is just where black paint has chipped off in tons of tiny places. I was able to get through in a couple places. and the aluminum underneath looked to be in decent condition. here are some before/after pics

BEFORE


AFTER

Why not just run it for a while and see what happens?

If it is slowing you down appreciably, then perhaps it must be removed. if it is just cosmetic, leave it on and don't worry about it. Go fishing.

If you want a pristine bottom on your boat, keep trying various chemicals until something dissolves it. Mostly, removing "stuff" on a surface can be accomplished by chemicals....or.....abrasion. Abrasion brings you back to scraping; sanding; etc.

Your boat. Make it the way YOU want it.

richg99