Bottom paint

[MikeSchinlaub]

@Chris1956 I'm not trying to sound like a know it all or anything, but this Bullet I'm working on shows what I'm talking about.
It's a bit hard to see the little ones at the front of the bunk, but they're all over the bunk areas.

 

[Chris1956]

Blisters are often caused by uncured resin in the hull mixing with water. I cannot tell from the photo what caused the damage you are seeing.

However, I have simple topside paint on the hull of my boat, and it sits on bunks on a lift, and I do not have any blisters in the paint, and gelcoat is much less susceptible than my paint to blisters. The OEM of the paint I used cautioned me not to leave the boat in the water for more than 3 days, as the paint would likely blister.

Furthermore, I have never seen blisters on trailered boats which sit on bunks.

Newer boats often have vinyl ester resin as the outermost layer of their hull. It is supposed to be more water resistant than polyester resin.