RE: method of keeping thru hull valves working smoothly, especially the forespar marelon models Before relaunching each year my wife goes around to each valve on the outside of the hull and sprays in Mclube Sailkote spray while I have each thru hull valve in the open and then closed position. I then exercise the valve and open and close a few time to ensure smooth operation. This process seems to work well for us. Pete Braveheart AT-34