(a) There must be an individual holding an MMC endorsed as Chief Engineer or other credential authorizing service as Chief Engineer employed onboard the following mechanically propelled inspected vessels:

(1) Seagoing or Great Lakes vessels of 200 GRT and over;

(2) Offshore supply vessels of more than 200 GRT;

(3) Inland (other than Great Lakes) vessels of 300 GRT or more, if the OCMI determines that an individual with a license or the appropriate MMC officer endorsement responsible for the vessel's mechanical propulsion is necessary.

(b) On vessels subject to STCW, the individual meeting the requirement of this section must also hold an STCW endorsement as Chief Engineer with the appropriate propulsion power for the vessel upon which they are operating, except as noted in § 15.105(g) for vessels on domestic near-coastal voyages.

(c) An individual engaged or employed to perform the duties of Chief Engineer on a mechanically propelled, uninspected, seagoing, documented vessel of 200 GRT or more must hold an appropriately endorsed MMC authorizing service as a Chief Engineer.