Claims

Backing plates for through-hull fittings are required when flanged seacocks must be bolted to the hull per ABYC rules; they are typically composite fiberglass plates bonded to the inside of the hull to provide attachment points without drilling additional through-holes, or older installations may use threaded machine screws on the exterior that are sealed and hidden under bottom paint.

Through-hull fittings and seacocks are required to pass a 500-pound load test per ABYC standards, likely because a person falling from above would generate forces far exceeding body weight, creating a safety margin against structural failure.

ABYC standards require two hose clamps on only two specific applications: flexible exhaust system component junctions and fuel fill hose connections (both at the deck fitting and at the tank); double clamping is NOT required on seacocks or most through-holes per ABYC rules, though ISO European standards differ.