What material are your thru hulls?
Before you do anything, you need to determine of what material your existing thru hulls are constructed.If you have brass thru hulls and you place bronze valves upon them, you set up a marvelous electrolysis between the two different metals, exasperated by the presence of salt water.If you have bronze thru hulls, the same applies if you use brass valves, although generally there are few of these used with thru hulls.I do not know of any fashion in which one may ascertain bronze as opposed to brass thru hulls when they are positioned on a vessel as both have non-magnetic properties.Hence, the general popularity and broad acceptance of the “plastic” or glass reinforced nylon or Marlon valves that avoid the electrolysis issues.However, the handles on these valves are subject to breaking unless disciplined greasing maintenance is performed on theses valves at least before launch and then at haul out. Further these valves should be opened and closed at least several times a week during the sailing season.The best fashion I know of to grease these valves is to use a spray can of Super Lube (yellow top) that is a synthetic lubricant that will not react poorly with the “plastic” parts of the valve as lubrications with petroleum distillates may have the tendency to do so.Close the valve, remove the hose on it, and then spray down onto the top part of the ball valve. Then go out side and spray onto the bottom side of the ball valve through the thru hull. Note that you could also use the solid form of Super Lube that comes in a can, however, this may be difficult to apply from the bottom without removing the valve.