Cracking bottom paint help

[TheSeanicRoute]

First time doing a bottom job on our boat and I need some advice. We have cracking in the paint that easily comes off to expose this brown bumpy layer. Is this down to the fiberglass or some kind of barrier coat? I was sanding with 60 grit paper on the remainder of the hull and it was looking good until this section. Do I need to patch gelcoat, sandblast, or chemically peel all this away? I don't want to do any damage! Thanks

[neilpride]

I see that you were removing the blue from the stern until you got there, so keep removing the blue because it seems to me that there is a patch of some repair, you will see more clearly when you have reached the third jack stand.

[tkeithlu]

I have the sneaky feeling that you are looking at fairing "mud," applied to smooth over a repair. If so, it has edges as neilpride suggests. I recommend that you take a look at the inside of the hull in the same area, see if it has been damaged/repaired, and make sure that if your boat did get torpedoed some time in the past that you are happy with the repair. Look particularly for any cracked structural members.

[boatpoker]

I think it may be multiple layers of patchy, very crudely applied, different types and different colour paints.
Sand that area til' smooth or til' the colour changes and post more photos.