- What This Certification Actually Is
- Who Issues It and Who Decides Your Modules
- Great Lakes and Inland vs. Inland: The Route Split
- The Six Preparation Groups in Detail
- Alternatives, Raises of Grade, and What Not to Count Twice
- Who Hires Masters of Vessels Under 500/1600 GRT
- Sequencing Your Preparation by Module
- Reading the Published Sources Correctly
- Frequently Asked Questions
- The National Maritime Center, part of the U.S. Coast Guard, issues this credential; your individual module list comes from your approval to test.
- The Great Lakes and Inland route uses six modules: Q100, Q320, Q321, Q322, Q323 and Q324.
- The Inland-only route uses five modules and omits Q324; Q100 or Q300 serves as the Rules module.
- Q100 and Q300 are alternatives. Never count both as simultaneous requirements.
What This Certification Actually Is
National Master 500/1600 GL and Inland, abbreviated NM51GI throughout this site, is a U.S. Coast Guard mariner credential for the person in command of a vessel operating on the Great Lakes and inland waters. The title describes the tonnage ceiling and the route. Unlike a vendor certificate you can earn from a training company, this is a federal licensing outcome, and the examination component is one gate among several the Coast Guard evaluates.
That distinction shapes how you should prepare. There is no single branded exam with one overall question count and one clock. Instead, the Coast Guard publishes a set of examination modules, each covering a defined subject area, and the combination you sit depends on your route and your circumstances. If you are still orienting yourself, the explainers What Is NM51GI? and What Does NM51GI Stand For? cover the naming, and this article focuses on how the exam structure actually works.
Who Issues It and Who Decides Your Modules
The governing body is the United States Coast Guard National Maritime Center (NMC). The NMC publishes its examination information on its public site, including module headings and topic matrices for Great Lakes and Inland endorsements. The relevant scope for this credential is identified in NMC materials as GLI03, covering master of vessels of less than 500/1600 gross register tons on Great Lakes and Inland routes.
Crucially, the NMC determines the individual applicant's assigned modules. Your approval to test is the authoritative document. Two mariners studying for the same title can sit different module sets, because prior endorsements, route choice and raise-of-grade status all feed into what you are actually required to pass. Before you invest weeks in any one subject, confirm the module list on your own approval.
For the eligibility side of the process, including sea-service and documentation prerequisites, see NM51GI Requirements 2026: Eligibility, Prerequisites & How to Qualify. For money questions, NM51GI Certification Cost 2026: Complete Pricing Breakdown discusses the cost picture; current fees should always be checked against NMC and Coast Guard fee schedules rather than assumed.
Great Lakes and Inland vs. Inland: The Route Split
The single most important structural fact about this credential is that it comes in two full-route variants, and they differ by exactly one module, plus a choice of Rules module on the restricted route.
| Route | Full-Route Module Set | Module Count |
|---|---|---|
| Great Lakes and Inland | Q100, Q320, Q321, Q322, Q323, Q324 | 6 |
| Inland | Q100 or Q300, Q320, Q321, Q322, Q323 | 5 |
Note the "or" in the Inland row. On the Inland route, Q100 (Rules of the Road: Inland and International) and Q300 (the Inland-only Rules module) are alternatives. You are not expected to pass both. The Great Lakes Topics module, Q324, is exclusive to the Great Lakes and Inland route and is not part of the Inland-only set.
These module counts describe the full-route structure. They are not a universal count of examinations for every applicant, since upgrades and route extensions change the picture. The domain-by-domain walkthrough is also covered in NM51GI Exam Domains 2026: Complete Guide to All 6 Content Areas.
The Six Preparation Groups in Detail
This site organizes the published modules into six route-aware preparation groups. They are unweighted: the sources do not assign percentages, so no domain should be treated as "worth" a particular share of your result. Each group below maps to published NMC module headings.
Domain 1: Rules of the Road: Inland and International (Q100)
Q100 is the Rules module that spans both inland and international rules. On the Inland route, the Inland-only Q300 is the applicable restricted-route alternative. Which one applies depends on whether a COLREGS limitation is in play for you, so check your approval.
- Right-of-way relationships, give-way and stand-on duties
- Lights, shapes, and day signals for the vessel types you will encounter
- Sound and light signals, including maneuvering and warning signals
- Differences between inland and international rules, and where each applies
- Conduct in restricted visibility and in narrow channels
Domain 2: Deck General (Q320)
Q320 covers broad deck seamanship and vessel knowledge expected of a licensed master. Expect applied material rather than trivia.
- Vessel terminology, construction basics and equipment familiarity
- Mooring, anchoring and line handling concepts
- General deck operations and shipboard routine
- Practical seamanship judgment
Domain 3: Deck Safety (Q321)
Q321 centers on safety management aboard. Candidates should be comfortable reasoning through scenarios rather than reciting lists.
- Emergency procedures and shipboard safety practices
- Firefighting, lifesaving and damage-related response concepts
- Safety equipment knowledge and its proper use
- Prevention-oriented thinking about hazards on deck
Domain 4: Navigation General: Great Lakes and Inland (Q322)
Q322 is the navigation theory module tuned to Great Lakes and inland operating conditions. It pairs naturally with the practical plotting module that follows.
- Aids to navigation and how they are used on these waters
- Chart interpretation and publications
- Navigation instruments and their limitations
- Route-specific piloting considerations
Domain 5: Navigation Problems: Chart Plot (Q323)
Q323 is the hands-on plotting module. This is where speed and accuracy with the tools matter, and where candidates who only read theory tend to struggle.
- Plotting positions, courses and distances on a chart
- Working time, speed and distance problems
- Applying variation and deviation to convert between true, magnetic and compass courses
- Interpreting set and drift in track-keeping
Domain 6: Great Lakes Topics (Q324), Great Lakes-and-Inland route only
Q324 is the module that separates the Great Lakes route from the Inland route. Published topics include piloting, compass error, meteorology and oceanography, maneuvering and handling including ice, stability, construction and damage control, and cargo handling.
- Piloting and compass error on large open-water lakes
- Meteorology and oceanography relevant to lake weather behavior
- Maneuvering and ship handling, including operations in ice
- Stability, construction and damage control
- Cargo handling
If you only read one deeper resource on how to attack these areas, make it NM51GI Study Guide 2026: How to Pass on Your First Attempt, which is built around the same module structure.
Alternatives, Raises of Grade, and What Not to Count Twice
The module list becomes confusing when upgrade and extension modules enter the discussion. Keep these rules straight.
- Alternative Rules modules are alternatives. Q100 and Q300 are never simultaneous requirements. Likewise, alternative Navigation General modules must never be counted together.
- Q326 is separate. Q326, Navigation and Deck General/Safety, is a raise-of-grade module for a mariner moving from a towing endorsement to Master under 500 GRT. It is not part of the original full-route set for most candidates.
- Route extensions are listed separately. The published guide lists Inland-to-Great-Lakes/Inland extension through Q324, and Q100 where a COLREGS limitation applies, as its own item.
- Upgrades are not extra domains. Separate upgrade, raise-of-grade and route-extension modules are not additional full-original-exam domains. They belong to a different applicant pathway.
Key Takeaway
Build your study plan from the module list on your approval to test, not from a forum post or a general module table. A mariner extending an Inland endorsement to the Great Lakes may need Q324 and little else, while a first-time applicant faces the full set.
Who Hires Masters of Vessels Under 500/1600 GRT
A Master 500/1600 GL and Inland credential opens command roles on vessels that operate within its route and tonnage limits. In practice, employers in this space tend to be operators of commercial vessels working Great Lakes and inland waterways, including passenger, excursion, ferry, charter, workboat and towing-adjacent operations, as well as harbor and utility services depending on the vessel's inspected or uninspected status and the specific endorsements held. The exact roles available to you depend on your sea service, your other endorsements and the operator's requirements.
This site does not publish salary figures for this credential because the sources reviewed do not establish them, and pay varies widely by operator, vessel type, seasonality and region. For a qualitative discussion of earning potential and career direction, see NM51GI Jobs, NM51GI Salary Guide 2026: Complete Earnings Analysis and Is the NM51GI Certification Worth It? Complete ROI Analysis 2026.
Sequencing Your Preparation by Module
Rather than a generic weekly template, here is a module-aware ordering that follows how the subject matter builds on itself. Adjust it to your assigned modules; if you are on the Inland route, simply drop the Q324 weeks.
Rules of the Road (Q100 or Q300)
- Start here because the rules vocabulary appears in nearly every other module's scenarios
- Drill lights, shapes and signals until recognition is instant
- Confirm whether your approval calls for Q100 or the Inland-only Q300
Navigation General (Q322) then Chart Plot (Q323)
- Study the theory first, then immediately practice plotting
- Repeat plotting problems until your tool handling is fast and clean
- Practice true/magnetic/compass conversions until they are automatic
Deck General (Q320) and Deck Safety (Q321)
- Work scenario-style reasoning rather than memorizing lists
- Link safety procedures to the vessel types you expect to command
Great Lakes Topics (Q324), if on your route
- Cover piloting, compass error, meteorology and ice handling
- Review stability, damage control and cargo handling
Integrated review
- Mix modules in timed practice to expose weak transitions
- Revisit your weakest module, not your favorite one
The reason Rules comes first and Chart Plot comes right after the navigation theory is that these two skills are the most hands-on and benefit most from repetition over time. Test your recall with the realistic question styles on the NM51GI practice test site, and keep a quick-reference sheet using NM51GI Cheat Sheet 2026: One-Page Review of Must-Know Facts.
Reading the Published Sources Correctly
The module structure described here comes from the NMC's public pages for Great Lakes and Inland endorsements, the GLI03 Master less than 500/1600 GRT page covering Q323 and Q326 materials, and the NMC Deck and Engineering examination guide. These sources were reviewed on October 11, 2026. A few cautions follow.
- The examination guide is the published document effective March 24, 2014, not a newly issued 2026 blueprint. Current indexed NMC matrices corroborate the module headings used here, but you should always verify against the live NMC pages.
- The relevant guide reference is section 2.1.2.2, printed page 25.
- These are issuer-published examination modules. This site organizes them into unweighted, route-aware preparation groups for study purposes only, and does not imply endorsement by the Coast Guard or the NMC.
- No percentages, single overall question count or duration, current fees or population pass rate are established by the reviewed materials.
That last point matters for expectations. If you want to understand what is and is not known about results, read NM51GI Passing Score 2026: Exactly What You Need to Pass and NM51GI Pass Rate 2026: What the Data Shows, and keep in mind that this article does not assert a population pass rate. For scheduling realities, see NM51GI Exam Dates 2026: Testing Windows, Deadlines & Scheduling, and for a candid look at difficulty, How Hard Is the NM51GI Exam? Complete Difficulty Guide 2026.
Frequently Asked Questions
For the full Great Lakes and Inland route, the published set is six modules: Q100, Q320, Q321, Q322, Q323 and Q324. For the Inland route it is five, with Q100 or Q300 serving as the Rules module and Q324 omitted. These counts describe the full-route structure, not every applicant's individual requirements.
No. Q100 and Q300 are alternatives, and alternative Rules modules must never be counted together as simultaneous requirements. Your approval to test indicates which one applies to your route and any COLREGS limitation.
Generally no. Q326, Navigation and Deck General/Safety, is a separate raise-of-grade module for moving from a towing endorsement to Master under 500 GRT. Upgrade, raise-of-grade and route-extension modules are not additional domains of the full original exam.
The National Maritime Center determines each individual's assigned modules. Your approval to test is the authoritative record, so confirm it before building a study plan.
The materials reviewed for this article do not establish current fees, a single overall question count or duration, or a universal passing percentage. Check the National Maritime Center's public pages and Coast Guard fee schedules directly for current figures, and see the site's articles on certification cost and passing score for context.