I recently aquired a 1972 O'DAy Mariner 2+2. After a severe storm I noticed water had entered along the seem between the uper and lower hulls. I estimated that over 100 gallons of water was inside. I also noticed blisters along the waterline of the outside of the hull. The bottom paint when I got the boat was in bad shape. There was thick areas and areas where it had worn off. Also you could tell that the last time it was painted the owner just painted over the old paint. The collor was dull and rough so I never noticed if Blisters were already present but I do know they were not along the waterline and now there is. I stripped the bottom paint and did a sanding with 100 grit sandpaper to highlight the high and low spots due to scratches, where bernicles had been scrapped off, and Gelcoat blisters. There are thousands of small marks that look like blisters that are smaller than a pencil eraser, but there are many that are bigger than a silver dollar. I do not plan on leaving the boat in water and trailer it every where I go. I was hoping someone with expertise could answer some of my questions. Some blisters are empty some filled with fluid and some are hard as a rock, Do I need to grind all of the blisters to allow them to dry? Do I have to grind the small ones? How deep do I grind (just through the Gelcoat or until I reach the seperation in the fiberglass)? What do you recommend to fill the holes? What should I use to seal the patches (gelcoat)? What would happen if I continued trailering the boat and didn't fix the blisters? Would a couple of coats of topside paint help seal some of the smaller blisters?