USCG Merchant Mariner Officer License (100 GT) Practice Test

To qualify, you typically need at least 360 days of relevant deck service on vessels. Of this, at least 90 days must be served on vessels of 50 GRT or more, and at least 90 days must have been within the last three years. Specific requirements can vary based on your experience (e.g., service on Great Lakes or inland waters vs. oceans). It is crucial to consult the latest USCG National Maritime Center (NMC) guidelines and have your sea service verified using the official CG-719S form to ensure you meet the precise, current regulatory standards.

Yes, the 100 GT License is a critical stepping stone. With additional sea service, completed assessments, and passing more advanced exams, you can upgrade to licenses such as Master 200 GT, Master 500 GT, and ultimately Unlimited Tonnage licenses. The experience and knowledge gained while holding and operating under your 100 GT License provide the foundational practical experience required for these upgrades. Each upgrade path has specific service time requirements at your current license level, which are detailed in the USCG's regulations.

The geographic scope of authority differs significantly. A 100 GT Near-Coastal license authorizes service up to 100 miles offshore from the U.S. coastline (including the Great Lakes). A 100 GT Inland license restricts service to inland waters, such as rivers, intracoastal waterways, and certain lakes, with no offshore authority. The exam modules are largely the same, but the chosen route will be endorsed on your license. Your qualifying sea service must correspond to the route you are applying for.

The merchant mariner credential (MMC), which includes your license, is typically valid for five years. To renew, you must meet specific requirements, including: (1) Submitting a complete application within 12 months before expiration, (2) Passing a comprehensive physical examination, (3) Providing proof of recent sea service (at least 90 days in the past five years) or completing a USCG-approved refresher training course, and (4) Meeting drug testing and background check standards. Timely renewal is essential to maintain your legal status to serve.

You must be proficient in fundamental stability concepts critical to vessel safety. Key topics include understanding the vessel's center of gravity (CG) and center of buoyancy (CB), the metacenter (M) and metacentric height (GM), and the factors affecting righting arms. You will be tested on calculating the effect of weight additions, removals, and shifts on vessel trim and list, using the TPI/MTI and moment-to-trim methods. A thorough grasp of these principles is non-negotiable, as stability is a core responsibility of the officer in charge.