46 C.F.R. § 15.915

The following MMC officer endorsements authorize the holder to serve as noted, within any restrictions on the MMC, and as provided by § 15.401:

(a) A Designated Duty Engineer (DDE) endorsement authorizes service as Chief or Assistant Engineer on vessels of less than 500 GT in the following manners:

(1) A DDE limited to vessels of less than 1,000 horsepower or less than 4,000 horsepower may serve only on near-coastal, Great Lakes, or inland waters.

(2) A DDE with no horsepower limitations may serve on any waters.

(3) When serving on a vessel to which STCW applies, the appropriate STCW endorsement must also be held.

(b) A Chief Engineer-Limited endorsement authorizes service as Chief or Assistant Engineer on vessels of any gross tons on inland waters and of less than 1,600 GRT on ocean, near-coastal, or Great Lakes waters.

(c) An Assistant Engineer-Limited endorsement authorizes service on vessels of any gross tons on inland waters and of less than 1,600 GRT on ocean, near-coastal, or Great Lakes waters.