I repaired a blistering problem on my boat this winter. The blisters were small, due to air bubbles in the gel coat finally blistering out. The job involved removing baltoplate, grinding the blisters, sealing (interprotect 1000), filling (Watertite), 2 coats of Interprotect 3000, 2 coats of 2000, and fresh Baltoplate (4 coats). Threw in a keel template job. Labor was about 200 hours (I did the work). Materials is roughly
$1,200. Note, baltoplate is not supposed to be sanded for environmental reasons, which might affect your decision. I bought a vacuum random radial sander and power planer for the job. You could also chose to just grind and fill the blisters (much less work) - which is what I'll do going forward if more appear.
