Able Seaman (AB) and Ordinary Seaman (OS) Information

With only a few exceptions an Ordinary Seaman or an Able Seaman
rating is required to work on all ocean going commercial vessels of
greater than 100 gross tons.

Ordinary Seaman (OS) is a rating that applies to both deck and
engine departments. This is an entry level rating that does not
require any sea service experience or training courses.

Able Seaman (AB) (46 CFR 12.401 through 12.409) is a deck
rating that requires qualifying sea service experience and training.
The AB rating that you receive will be based on your qualifying sea
service experience. All AB ratings require the mariner to complete an
approved Lifeboatman (Proficiency in Survival Craft) Course.
  • AB Unlimited requires 1080 days of qualifying sea service
    experience on the deck of vessels operating on ocean waters.
  • AB Limited requires 540 days of qualifying sea service
    experience on the deck of vessels greater than 100 gross tons
    operating on ocean waters.
  • AB Special requires 360 days of qualifying sea service
    experience on vessels operating on the federally navigable
    inland waters of the US or on ocean waters.
  • AB Fishing requires 180 days of qualifying sea service
    experience on the deck of vessels operating on ocean waters
    or the federally navigable inland waters of the US.
  • AB OSV (Offshore Supply Vessel) requires 180 days of
    qualifying sea service experience on the deck of vessels
    operating on ocean waters or on the federally navigable inland
    waters of the US.
  • AB Sail requires 180 days of qualifying sea service experience
    on the deck of sailing vessels operating on ocean waters or on
    the federally navigable inland waters of the US.
Advancement

A mariner can advance from OS to either the deck department as AB
(Able Seaman) or to the engine room as QMED (Qualified Member of
the Engine Department). Advancement requires both sea service
and either an approved course or completion of exams at a Coast
Guard Regional Exam Center (REC).

Advancement from one AB rating to another higher AB rating can be
accomplished with qualifying sea service experience alone.

Able Seafarer Deck

The 2010 Manila Amendments to the STCW convention established
an STCW endorsement equivalent to the MMC Rating Endorsement
of Able Seaman. This endorsement is called Able Seafarer Deck. US
mariners holding a the rating endorsement AB should check to see if
they also qualify for this new STCW endorsement.

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