The story with VC-17
I've used only VC-17 since I had my boat, which I kept it in fresh water for the first three years I owned it. Three coats of VC-17 lasted about 18 months. However, it wore faster near the waterline where the algae was growing. Now I sail in salt water but I store the boat on the trailer so the paint will last longer.VC-17 is a thin teflon-based paint designed for use in fresh water or salt water where the potential for fouling (barnacles) is low. The hard, smooth finish is supposed to allow the boat to slip faster through the water. It holds off the barnacles OK, but it won't resist algae, slime or other aquatic plant growth.It sounds like you had a pretty decent growth of slime. You didn't say how many coats you had applied so it's hard to say whether or not you got your money's worth. Because VC-17 is so thin and soluble, you need at least three coats for some durability. Five coats is probably better at the bow, the leading edges of the keel and rudder and other high flow areas. That's actually pretty easy to do, because the paint dries so fast; in fact I mix it in a 44 oz plastic ketchup bottle and squeeze it onto the roller as I need it just to keep it from drying out. If you put the boat on a sling, the whole thing can be done in a day. I set the boot top about two inches above the actual waterline, so I can repaint or touch up at any time without ever having to retape.One more thing...don't let the paint come in contact with the rudder bracket, as the copper in the paint will cause galvanic corrosion and pit the aluminum (guess how I figured that one out). Good luck.PeterH23 "Raven"