Protective coating or just a stain

[Lonepiper]

On the very bottom surfaces of my MFG Gypsy, there is a dark coating of some sort. It doesn't seem to be a natural forming stain as it is only on the bottom surfaces, not on the sides. Is this something I should leave alone when refinishing or should I sand this surface also for repainting? I have tried to show it in the image below but it's difficult.

 

[Bob_VT]

Re: Protective coating or just a stain

Been there - done that

Get a sponge and some good cleaner..... scrub a spot...... is it like tar? Looks black? I would really bet it is lake scum from never being cleaned.

I had that on an old tri-hull and I spent days getting it off. I asked people what it was and one friend told me it was grease from being in the water

 

[Lonepiper]

Re: Protective coating or just a stain

I have been using a orbital sander with 120 grit to work on the top side. I tapped the back area with that and it came right off. What puzzles me is that it's only on the bottom, not on the sides.

 

[Bob_VT]

Re: Protective coating or just a stain

Well.... if I were you and you sand it off lightly ...... I will bet you pick up 1-3 mph in your top end.