Blisters are for newbies...
The old timers have to deal with hydrolysis and dry laminates that is the bane of these poorly made Far East trawlers from the 70's and 80's..
Seriously...your boat can be a hit or miss situation...but you just don't know the extent of the problem without coring or grinding deep.
Taking off the paint and barrier coating over gel coat can be an expensive mistake if you really have a severe blister or hydrolysis problem.....as they will just return with a vengeance.
Many boats can have severe hydrolysis without blisters...usually ones where the gel was so bad that water passes freely in and out of the laminates without enough pressure building to cause a blister.