OUPV, Master 25 GRT, Master 50 GRT, Master 100 GRT — compared side by side so you know exactly which license to get and why.
All federal captain licenses are governed by 46 CFR Part 11 and issued by the National Maritime Center (NMC) as endorsements on your Merchant Mariner Credential (MMC). The main categories are deck officer licenses (OUPV and Master), engineering licenses (Designated Duty Engineer, Chief Engineer), and a few specialty ratings.
For most people getting into charter fishing, sailing instruction, water taxi, or recreational guiding, the relevant licenses are OUPV and the various Master tonnage levels. The license you need depends on: how many passengers you carry, the size of your vessel, whether the vessel is inspected, and the waters you operate on.
6
Max passengers on OUPV (6-Pack)
100
GRT ceiling for most near-coastal licenses
5 yrs
License validity before renewal
| License | GRT Limit | Passengers | Vessel Type | Sea Service |
|---|---|---|---|---|
| OUPV (6-Pack) | < 100 GRT | Max 6 | Uninspected | 360 days |
| Master 25 GRT | ≤ 25 GRT | Unlimited | Inspected | 360 days |
| Master 50 GRT | ≤ 50 GRT | Unlimited | Inspected | 360 days |
| Master 100 GRT | ≤ 100 GRT | Unlimited | Inspected | 360 days |
| Mate 200 GRT / Master 200 GRT | ≤ 200 GRT | Unlimited | Inspected | 720 days |
Waters column omitted for brevity — see the Waters section below. All licenses require TWIC, physical, drug test, CPR, and application fee.
Gross Register Tons (GRT) is a measure of a vessel's total enclosed internal volume — expressed in units of 100 cubic feet. It is not displacement, weight, or how heavy the boat feels. A 35-foot sport fisher might measure only 18–22 GRT. A 50-foot catamaran charter boat might measure 45–60 GRT.
The GRT figure that matters for your license is the measurement on the vessel's USCG documentation certificate or state registration. Most recreational and light charter boats are comfortably under 100 GRT, which is why the Master 100 GRT license covers the vast majority of near-coastal commercial operations.
Rule of thumb
If the boat looks like a charter fishing boat, day-sailor, or water taxi you have seen at a marina, it is almost certainly under 100 GRT. Very large expedition yachts, ferries, and commercial vessels start pushing into 200 GRT and above.
Rivers, lakes, bays, harbors, and waters inside the baseline (the line connecting outermost headlands). If you are in a protected harbor or river, you are on inland waters.
Waters from the baseline out to 200 nautical miles offshore. However, OUPV and most entry-level Master licenses are limited to 100 nautical miles offshore. This covers the vast majority of charter and commercial activity.
The five Great Lakes and connecting waters. Treated as a separate category under CFR Part 11 with some distinct requirements from the Inland and Near-Coastal routes.
Unlimited — any ocean waters, any distance offshore. Requires more sea service and more exam content. Most near-coastal operators never need an Oceans endorsement.
A base OUPV or Master license authorizes operation of a power vessel. Endorsements extend what you are authorized to do. They appear on your MMC alongside your base license.
Authorizes operation of uninspected vessels propelled primarily by sail. Required to carry passengers for hire aboard a sailboat. Added to any OUPV or Master license after demonstrating sailing proficiency.
Authorizes commercial towing operations. Requires completion of the TOAR (Towing Officer Assessment Record) and dedicated sea service in towing. Available as a full towing or limited towing endorsement.
A lighter version of the towing endorsement for incidental towing on day trips — think Sea Tow or TowBoatUS-type operations. Fewer requirements than the full towing endorsement.
Five common scenarios — find the one that matches your situation.
I want to take fishing parties out (6 or fewer people)
OUPV (6-Pack)The standard 6-Pack is all you need for charter fishing with up to six paying passengers on an uninspected vessel.
I want to operate a charter boat with more than 6 passengers
Master 100 GRTOnce you exceed six paying passengers you need an inspected vessel and a Master license. Master 100 GRT is the most practical choice for most operators.
I want to captain a sailing charter
OUPV + Sailing Endorsement or Master + Sailing EndorsementA base license alone does not authorize operation under sail. You must add the sailing endorsement to carry passengers aboard a sailing vessel.
I want to do commercial towing
OUPV or Master + Towing EndorsementTowing requires completion of the TOAR (Towing Officer Assessment Record) and additional sea service in towing. Add this endorsement to any base license.
I want maximum flexibility and career options
Master 100 GRTThe Master 100 GRT near-coastal license is the most versatile entry-level Master credential. It covers inspected and uninspected vessels, any passenger count, and qualifies you for a wide range of commercial positions.
If you already hold an OUPV license, you can upgrade to a Master license without starting from scratch. The NMC gives credit for your existing sea service and allows you to test only the additional exam sections required for the Master endorsement.
Accumulate additional sea service
An upgrade from OUPV to a Master license requires documentation of the requisite sea service days in the appropriate capacity. Sea service forms must be signed by a vessel owner or supervisor.
Pass additional exam sections
Master license exams include additional sections beyond the OUPV exam — covering topics such as stability, cargo operations, and advanced navigation at the applicable tonnage level.
Submit an upgrade application to the NMC
Submit a complete upgrade application through the Merchant Mariner Credentials portal. Your existing MMC credential is surrendered and a new one issued with the upgraded endorsement.
OUPV stands for Operator of Uninspected Passenger Vessel — commonly called the 6-Pack license because it limits you to carrying a maximum of six paying passengers. It is issued under 46 CFR Part 11 and allows operation of uninspected vessels under 100 gross register tons on near-coastal or inland waters. It is the entry-level federal captain's license and the most commonly obtained.
The OUPV limits you to six paying passengers on uninspected vessels. The Master 100 GRT allows you to carry any number of passengers on inspected vessels up to 100 gross register tons on near-coastal waters. If you want to operate a charter boat with more than six passengers — such as a party boat, ferry, or large sailing charter — you need at least a Master license. The Master 100 GRT also opens doors to more commercial employment opportunities.
Gross Register Tons (GRT) is a measure of a vessel's total enclosed internal volume — roughly the cargo capacity — expressed in units of 100 cubic feet. It is not the same as the vessel's weight or displacement. For most recreational and light charter boats, GRT is much lower than you might expect. The majority of center consoles, sport fishers, and day-charter sailboats are well under 100 GRT. Your license's GRT limit determines the maximum size vessel you are authorized to operate.
Deep dive into the differences, when to upgrade, and what each license actually lets you do
How to document sea service days, what counts, and how to fill out the NMC forms
Section-by-section study strategy and exam-day advice for first-time candidates
All four exam sections, passing scores, prerequisites, and what to bring to the test center
1,628+ USCG exam questions, spaced repetition flashcards, and section-by-section progress tracking — free to try, no account required.
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