Straight off the national maritime website.
Looks like you need 50 percent of days over 1600, then the rest over 100 tons.
Recency – 90 days in the past 3 years on vessels over 100 GRT to include 45
days on vessels over 1,600 GRT.
11.201
MSM
3rd MATE 46 CFR
1080 days of service in the deck department on Ocean/NC or Great Lakes self-
propelled vessels, OF WHICH
- 180 days of bridge watchkeeping duties under the supervision of the
master or a qualified officer.
11.407
Experience gained in the engine department on vessels of appropriate tonnage
may be creditable for up to 90 days of the service requirements OR
11.407
Graduation from a maritime academy:
USMMA (deck curriculum),
USCGA / USNA (with qualification as DWO or OOD),
Deck class of:
California Maritime Academy, Maine Maritime Academy, State
University of NY Maritime College, Texas Maritime Academy of
Texas A&M University of Galveston, Massachusetts Maritime
Academy or GLMA w/ocean option program (GLMA w/o ocean
service will be allowed to test for NC); OR
11.407
Satisfactory completion of a comprehensive apprentice mate training program
approved by the Coast Guard, OR
11.407
360 days as master on vessels of more than 200 GRT upon Ocean/NC waters
while holding an Officer endorsement as Master less than 1600 GRT
Ocean/NC (tonnage limitation WILL apply)
11.407
NOTE: Service towards an Oceans, NC endorsement will be credited as
follows:
-
-
- Service on GL will be credited day for day.
Service on inland waters, other than GL, may substitute for up to 50%
of the total required service.
Service on vessels to which STCW applies (inland or NC) will be
credited day for day.
11.401
A Master or Mate of GL &/or Inland of AGT, may obtain this endorsement by
completing the prescribed examination.
11.407
Unlimited Tonnage 46 CFR
All required service is on vessels of 100 GRT or more AND 11.402
50% of the required service is on vessels 1600 GRT or more or a tonnage
limitation may apply (see Tonnage Limitation below).
Any sea service on ATB’s, dual or push mode ITB’s or any towing vessel with
barges, refer to 46 CFR 11.211 (d) and NVIC 2-81 for tonnage calculation.