I just took the boat cover off of my pontoon boat(yes I know its not a performance boat but it keeps my St Bernard of my miller) and the seats were all dark in color. I thought it was just dirt but it would not clean. after removing the cover for 2 days the dark color went away. When I covered it again and took it off to use the dark color returned only to go again in a couple of days. I'm going to sell the boat but won't stick someone with a problem. I understand this is common here in havasu in boats stored outside with covers. Does anyone have a cure other then new interior. Oh by the way my St Bernard will just have to play in the pool but don't think it's smart enough to swim.