On board small passenger vessels the minimum fill pipe size for a gasoline or diesel tank is __________.

Correct Answer: Option D — 1 1/2 inches nominal pipe size

Per 46 CFR 182.440, the minimum nominal pipe size for gasoline or diesel fuel fill pipes on small passenger vessels is 1 1/2 inches. This diameter is specified to ensure adequate flow rates during refueling, preventing backpressure that could lead to fuel spillage or dangerous overflows on deck.