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large areas of the hull below the waterline are covered with hundreds of small blisters.<<

WOW!!! Dunno what's happened unless there's been a change in materials. My former Stargazer a 1979 M-17 was in the water for 4 years ( Lake Lanier, Ga) and in the Gulf for about a year before I bought her. No blisters either time. Harvey/ Ga