Mismatching valves or other fittings on thru-hulls is not good practice and when done below the maximum heeled waterline, it increases the odds for failure and water intrusion. It is this risk to boats that provided the impetus for the American Boat and Yacht Council (ABYC) to develop standards for the installation of thru-hulls. They state, “When installed below the maximum heeled waterline, a thru-hull must have a valve mounted so that the system will withstand a 500-pound static force applied for 30 seconds to the inboard end of its connecting fitting.” But where exactly is the “maximum heeled waterline?”…