I was looking through the latest issue of Boating magazine and learned that Meridian Yachts uses internal gutters on the topsides of their 441 motor yacht to pipe the rain water overboard via a drain under the swim platform, specifically to prevent black streaks. Thought it was clever and it sort of answers the question: "Has anybody found a way to prevent or reduce black streaks on their boats?"
I also learned that the 441 will plane at only 11 MPH. I imagine it would be awesome for wakeboarding up in quiet coves, like Winter Harbor.