I have a friend who recently purchased an '88 MacGregor D that sat on its trailer most of its life. It still had the original 3 year state registration decal on the hull ('91). The hull had a beautiful mirror finish. The bunks had rotted and were temporarily with replaced with 2x4s, blanket strips, and zip ties to get the boat home. After putting the boat on blocks to refinish the trailer, blisters were discovered only where the bunks were.
Evidently, over the years, the weight of the boat had pushed the water (rain water) from the carpeted bunks into the fiberglass. The boat appears to have be parked in a shaded area while stored. This is the only conclusion we have been able to come up with.
BTW, after a month of detailing, we put the boat in the water and the performance was unreal. Roger nailed it with this design. Almost makes me want to trade my X for a D. (Nope, can't give up the 140 hp yet. But maybe a 2nd Mac?)
May want to check the bunk areas in your bottom one day.
