46 CFR §15.865

1. (a)Every person serving under the authority of a rating endorsement as Qualified Member of the Engine Department (QMED) on any United States vessel requiring QMED must hold an endorsement as QMED.
2. (b)On vessels subject to STCW, certain seafarers meeting the requirement of this section must also hold either an STCW endorsement as Able Seafarer-Engine or Rating Forming Part of an Engineering Watch (RFPEW) or designated to perform duties in a periodically unmanned engineroom (according to § 15.404(c) and (d)), except as noted in § 15.105(g) for vessels on domestic near-coastal voyages.