Blisters common
People seem to be avoiding this topic. You have a big job on your hands. Looks like paint adhesion has failed over a lot of the bottom. You also have blisters. In the fall, get somebody to blast off all old paint down to gelcoat. Puncture the blisters and allow them to dry out then fill them. In the spring, apply barrier coat then new bottom paint. Reminds me of the script instruction for a movie. "House implodes." Two words. Implementing them is something else.
Blisters are a common boat bottom problem.
I would vary the aforementioned procedure to sand hull to gel coat and not sand blast. Blisters ground out then soap and water wash, then acetone wash, then leave on stands for several months for hull to dry. Heaters inside of cabin help dry out hull.
During the drying time, it would be good to wash hull as described above and wash as above before filling blister holes. Blisters leach or bleed an aciditic liquid and soap and water washes away residue while acetone sucks residue causing blisters from frp.
Blister holes can either be filled with epoxy paste or vinyl ester paste. I have gotten impression that vinyl ester paste sticks best. Then hull should be faired.
Since your boat has a history of paint not adhering, consider painting hull first with penetrating epoxy a.k.a. thin epoxy as base coat as in several coats. Then apply barrier coats as in several coats, then your choice bottom paint.
Thin epoxy is used as a primer for problem finishes to allow for epoxy barrier coating to adhere.
With blister repair getting the hull dry is important.
If you want to sail this season, I would just clean hull as best you can and apply one coat of bottom paint. Then come fall do as above to fix serious issues. Life is to short not to sail for a summer.
Fair Zyphyrs,
Ed K
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