AB Rating Requirements: Earning Your Able Seaman Endorsement
The Able Seaman endorsement is the senior unlicensed deck rating in the US merchant marine. This guide explains the AB classes, their sea-time requirements, training, and the exam.
The Classes of AB
The USCG recognizes several classes of Able Seaman scaled by sea time and route. AB-Special generally requires the least sea time and is the common first target; AB-Limited and AB-Unlimited require progressively more service on larger vessels and broader routes. There are also endorsements like Able Seafarer-Deck that align the rating with STCW for international service.
Sea-Time Requirements
AB sea time is measured in documented days of qualifying service aboard vessels of appropriate size and route, with AB-Special requiring the fewest days and AB-Unlimited the most. A day of service is generally tied to watchstanding or equivalent shipboard duty, and service on smaller vessels may count at reduced rates. All of it must be recorded on Sea Service forms signed by your employer.
Training Requirements
AB applicants typically need survival craft / lifeboatman training appropriate to the endorsement. Mariners intending to sail internationally will also need STCW Basic Safety Training. Confirm which specific training your target AB class and intended trade require before scheduling courses.
The AB Exam
The NMC administers the AB examination, which you can schedule through a Regional Exam Center. It covers seamanship, cargo handling, safety, and watchstanding competencies. Study guides are available from the NMC and commercial publishers, and many mariners prepare with a review course before testing.
Special Endorsements to Add
AB is also a launchpad for valuable add-on ratings: Tankerman-Assistant for tank-vessel cargo work, Lifeboatman-Limited for survival craft duties, and others. Stacking endorsements on your MMC increases the range of vessels and roles you can fill and directly improves employability.
A note on requirements
Credentialing rules change and often depend on your specific vessel, route, tonnage, and history. Nothing here is legal advice. Always confirm the current requirements with the USCG National Maritime Center (NMC) and with your employer or vessel operator before making career or hiring decisions. When a rule seems to conflict with your situation, an NMC deficiency letter or a call to the NMC Customer Service Center is the fastest way to get an authoritative answer.