(a) The provisions of this subpart shall apply to the following vessels:
(1) All vessels of 100 gross tons and over.
(2) All vessels which carry more than 150 passengers.
(3) All vessels on an international voyage.
(b) The provisions of this subpart, with the exception of Sec. 72.05-90, shall apply to all vessels noted in paragraph (a) of this section contracted for on or after May 26, 1965. Such vessels contracted for prior to May 26, 1965, shall meet the requirements of Sec. 72.05-90.