In accordance with 46 CFR 61, for a passenger vessel, what is the interval in years between when hydrostatic tests must be performed on an oil-fired water-tube auxiliary boiler as witnessed by a marine inspector?

Correct Answer: Option C — 2.5

Under 46 CFR 61.10-5, passenger vessels must undergo hydrostatic testing for oil-fired water-tube auxiliary boilers at intervals not exceeding 2.5 years. This testing, witnessed by a marine inspector, ensures the pressure boundary integrity of the boiler, which is critical for the safety of the vessel and its passengers.