USCG Master 100 Ton License — Requirements, Exam, and Prep Guide

Rules of the Road — 90% required

International COLREGS and Inland Rules. This is a closed-book section with no reference materials. Topics include: right of way between vessel types, lights and shapes requirements, sound and light signals, restricted visibility rules, narrow channels, traffic separation schemes, and definitions. Requires 45 out of 50 correct answers.

Study resource: COLREGS Study Guide

Deck General and Safety — 70% required

Broad coverage of practical seamanship and vessel safety. Topics include: lifesaving appliances (life rafts, EPIRBs, immersion suits), firefighting equipment and techniques, stability theory, anchor handling, mooring, line types, knots, engine room basics, distress signals, marine law, and passenger safety procedures.

Navigation General — 70% required

Applied navigation theory and practice. Topics include: buoyage systems (IALA-B), chart symbols, compass deviation and variation, tidal calculations, current effects, GPS and electronic navigation concepts, VHF radio procedures and DSC, weather interpretation, and aids to navigation.

Chart Plotting — 90% required

Hands-on practical navigation using paper charts, parallel rulers or plotter, and dividers. Problems include: plotting a course from point A to B, applying variation and deviation, determining speed-time-distance, fixing position using bearings, calculating set and drift from current, and identifying danger bearings. You must score 9 out of 10 correct. The exam is open chart but closed to outside reference materials.

First aid certification

Must be current at time of application. Accepted from American Red Cross, American Heart Association, American Safety and Health Institute, and most accredited first aid training programs. Standard course is approximately 8 hours. Certification valid for 2 years.

CPR certification

Basic CPR/AED certification required. Can be combined with first aid in a single course. Many marinas, fire departments, and community centers offer one-day combined first aid and CPR courses. Certification valid for 2 years.

Physical examination

Conducted by any licensed physician using USCG Form CG-719K or equivalent. Examines vision (corrected or uncorrected), color vision (required for navigation light recognition), hearing, and overall fitness for sea duty. There is no USCG-approved physician list — any licensed MD or DO can perform the exam. Valid for 2 years.

Drug screening

DOT 5-panel urine drug test through a SAMHSA-certified laboratory and DOT-qualified collection site. Must be within 185 days of application submission. The test screens for marijuana, cocaine, amphetamines, opioids, and PCP. Results from employer-required random testing programs are not accepted — must be an applicant-initiated pre-employment test for MMC purposes.

Timeline — building sea time

If you are starting from zero, reaching 720 days of sea service is the longest phase. Working full-time on a commercial vessel you may accumulate 250 to 300 documented days per year. Working part-time or seasonally it may take 5 to 8 years. For those already in the industry, many Master candidates have the sea time before they begin the paperwork.

Timeline — exam prep

Most Master candidates spend 6 to 12 weeks on focused exam prep. OUPV holders upgrading to Master only need to prepare for Master Deck and Master Navigation, which can take 3 to 5 weeks with consistent daily study. First-time applicants without a prior OUPV need to cover all 6 sections and should plan 8 to 12 weeks minimum.

Timeline — NMC processing

After submitting a complete application, current NMC processing takes 4 to 12 weeks. Rush processing is not available. Applications with missing documents are returned, resetting the clock — verify your package is complete before submitting.

Sea service for renewal

Must document at least 360 days of sea service during the validity period, or pass the relevant exam sections again. Captains who have been inactive can renew by reexamination rather than sea service.

Physical and drug test

Updated physical examination and drug test are required at each renewal. First aid and CPR certifications must also be current.

Expiration and reactivation

If your MMC expires, it can generally be reactivated within one year of expiration with the renewal documentation. After one year lapsed, you may be required to reexamine. An expired MMC cannot be used for commercial operation.

Do I need the Master 100 ton license to run a charter boat?

It depends on passenger count and vessel type. If you carry 6 or fewer paying passengers on an uninspected vessel, the OUPV (Six-Pack) is sufficient for most operations. If you carry 7 or more passengers, operate an inspected vessel (one with a USCG Certificate of Inspection), or work on certain vessel types like ferries or crew boats, you need the Master. When in doubt, contact your local USCG Marine Safety Office.

Is the Master 100 GRT the same as a 100-ton license?

Yes — the terms are interchangeable. The official USCG designation is Master 100 GRT (Gross Register Tons), but it is commonly called the 100-ton license or Master 100-ton in the industry. The tonnage refers to the vessel size limit, not the weight of cargo.

Can I use time on a sailboat toward sea time?

Yes. Time on sail-propelled vessels counts toward sea time requirements. The vessel must be 26 feet or longer and you must be underway for at least 4 hours to count a day. If you are seeking the Sailing endorsement, your sailing sea time also counts toward that endorsement.

What happens if I fail an exam section?

You must wait 30 days before retaking a failed section. You are allowed up to 3 attempts total for each section within the application validity period (typically 1 year). After 3 failures you must restart the application process. This makes solid exam preparation critical before you schedule your REC appointment.

Does recreational boating time count toward sea service?

Yes, recreational time on your own vessel counts if it is properly documented. You must maintain a contemporaneous log with dates, waters, vessel name, and hours underway. The NMC accepts self-certified recreational sea service statements. Commercial sea service documented by employer letters is generally preferred and less likely to be questioned.

How do I find my nearest Regional Examination Center?

The USCG maintains a list of RECs on the NMC website at uscg.mil/nmc. Major RECs are located in Boston, New York, Baltimore, Miami, New Orleans, Houston, Seattle, San Francisco, Honolulu, and other maritime cities. Some RECs accept walk-in appointments; others require advance scheduling. Call ahead.