To John Kivel;We have the other 170 berthed on the other side of Dave and Debbies boat. I was searching for a way to get the dark stains off our deck and came across your post regarding the boat next to yours. She (Debbie) uses 409 to clean the hull each time they finish sailing. I had a good laugh and knew instantly it had to be Debbie. I have tried to get her to do mine but Dave insists on my buying his beer while she works and he says she takes a long time (lot of beer). I didn't think I could afford it. Anyway, we tried the 409 treatment and it cleaned the boat but didn't do much for the dark stains and streaks. Guess you have to do it every time. In any case we are going to move on to the wax method. Midwest Sailing has a good wax with a very fine abrasive cleaner. I'll let you know how it works. Trouble is, as long as there is wind, who wants to be cleaning in lieu of sailing. Especially the 170 as it is a lot of fun to sail. Best boat I have had.