1974 Bonito Tri-hull Saltwater Black Spots

[JoeyLeppien]

Hey everyone, I've had this 1974 Bonito tri-hull for about 9 months now. I live on a saltwater canal in Florida and sometimes keep the boat in the water for a week or so. I'm usually real good about taking it out frequently and giving the hull a good clean.
I just pulled my boat out and after cleaning the hull, these black spots remain. I've been told that it may be the barnacles permeating my gelcoat.
Does anyone have any input on what I should do to remove the spots and get the hull back to looking decent? My friend who details boats for a living told me that it wouldn't hurt to add an epoxy barrier coat and some bottom paint to it as well.

Thanks in advance, this is my first boat so I'm still doing my best to learn about all of this!

 

[silverbul]

if it were me, i would try a green wet scuffy pad, try it on a spot not well seen. lmo