46 CFR 120.312: Power sources on vessels of more than 19.8 meters (65 feet) in length carrying more than 600 passengers or with overnight accommodations for more than 49 passengers.

A vessel of more than 19.8 meters (65 feet) in length carrying more than 600 passengers or with overnight accommodations for more than 49 passengers must have:

(a) Two generator sets;

(b) An electrical power system that complies with the requirements of §§ 111.10-4, 111.10-5, and 111.10-9, in subchapter J of this chapter;

(c) A final emergency power source, as defined by § 112.01-20 in subchapter J of this chapter, with sufficient capacity to power the loads listed in § 112.15-5 in subchapter J of this chapter for three hours; and

(d) The final emergency power source located outside the machinery space.