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Able Seaman (AB) General, Sea Service and Other Requirements by U.S. Coast Guard

able seaman ab

An Able Seaman (AB) is a merchant marine rating of the deck department of a merchant ship and is a crew member who is below the Officer who holds a Merchant Mariner Credential (MMC) in the deck department. An AB can work as a watchstander or a day worker. The AB can apply to become an Officer after sufficient sea service. USCG specifies different kind of rating in accordance with the duties involved and seagoing experience -

AB Unlimited: AB Unlimited is qualified for unlimited service on a vessel on any waters, is at least 3 years service on deck on board vessels operating at sea or on the Great Lakes. Unlimited means an annotation on an MMC authorizing service on vessels of any tonnage or any propulsion power.

AB Limited: AB Limited is qualified for limited service on a vessel on any waters, is at least 18 months service on deck on board vessels of at least 100 gross tons or an alternate tonnage prescribed operating on the oceans or navigable waters of the United States (including the Great Lakes).

AB Special: AB Special is qualified for special service on a vessel on any waters, is at least 12 months service on deck on board vessels operating on the oceans or the navigable waters of the United States (including the Great Lakes).

AB OSV: For service on a vessel of less than 500 gross or an alternate tonnage prescribed and engaged in support of exploration, exploitation, or production of offshore mineral or energy resources. An individual may be rated as able seaman-offshore supply vessels (OSV) if the individual has at least 6 months service on deck on board vessels operating on the oceans or the navigable waters of the United States (including the Great Lakes).

AB Sail: For service on a sailing school vessel on any waters, an individual may be rated as able seaman-sail if the individual has at least 6 months service on deck on sailing school vessels, oceanographic research vessels powered primarily by sail, or equivalent sailing vessels operating on the oceans or navigable waters of the United States (including the Great Lakes).

AB MODU: The Ordinary Seaman with an experience of one year on vessels at least 65 feet in length is eligible to be an AB-MODU for use in a mobile offshore drilling unit (MODU) for well operations.

ableseaman deck duties

You may also read: International Maritime Organization (IMO) STCW requirements for Able Seafarer (Deck)


General Requirements for USCG National Able Bodied Seaman

  • Age: 18 years of age.
  • TWIC (Transportation Workers Identification Card)
  • Medical Certificate
  • Drug testing compliance (within 6 months)
  • Sea Service letters or discharges (Must verify vessels in MISLE)

USCG AB Seaman Sea Service Requirements

  • AB Unlimited - 1080 days deck service on Oceans or Great Lakes
  • AB Limited - 540 days deck service on vessels of 100 GRT or more, not exclusive to rivers & smaller inland lakes of the United States
  • AB Special - 360 days deck service on navigable waters of the U. S.
  • AB OSV - 180 days deck service on navigable waters of the U. S.
  • AB Sail - 180 days of deck service on sailing school vessels, oceanographic research vessels powered primarily by sail or equivalent sail vessels on any navigable waters of the U. S.
  • AB MODU - 360 days of service on vessels 65 feet or over on any navigable waters of the U.S.

Other Requirements and Exams

  • Qualify as Lifeboatman or Lifeboatman-Limited
  • Exams or Course Completion Certificate

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