- What National Master 100 GL and Inland (NM1GI) Actually Is
- Who Governs It and Where the Rules Live
- Why Your Route Changes the Exam
- The Five Preparation Groups
- Rules of the Road: Choosing Q100 or Q300
- Deck General (Q347): Seamanship and Ship Handling
- Deck Safety (Q348): Stability, Fire, and Emergencies
- Navigation General (Q349) and Chart Plot (Q350)
- Where Q352 Fits for Raise of Grade
- Sequencing Your Preparation
- Where This Credential Gets Used
- Frequently Asked Questions
- NM1GI here means National Master 100 GL and Inland, a U.S. Coast Guard National Maritime Center credential for vessels under 100 GRT.
- The exam is built from five route-aware preparation groups, not one fixed universal test.
- Your NMC approval to test, not a study guide, determines your assigned modules and any credit.
- Heavy-weather and lifeboat/liferaft launching topics are flagged as Great-Lakes-specific in the NMC table.
What National Master 100 GL and Inland (NM1GI) Actually Is
NM1GI refers to the National Master 100 GL and Inland credential: a mariner's license endorsement authorizing service as Master or Mate on vessels of less than 100 gross register tons (GRT) operating on the Great Lakes and inland waters. The NMC tracks the examination for this endorsement under the code GLI06, titled Master or Mate Less Than 100 GRT.
For this article, the identity is fixed: this is a Coast Guard mariner credential, not a vendor certification, not an IT or finance designation, and not any other credential that happens to share the acronym. If you arrived here from a search for a different NM1GI, the details below will not apply to you. The sibling pages on what NM1GI stands for and the meaning of NM1GI cover the naming question in more depth.
The word "Master" matters. Candidates in this route are preparing for the Master identity, which is the senior deck authority for a small vessel: the person responsible for navigation, safe operation, crew, and compliance. The exam reflects that responsibility by combining navigation rules, seamanship, emergency response, and chart work into one assessment path.
Who Governs It and Where the Rules Live
The governing body is the United States Coast Guard National Maritime Center (NMC). Everything about what you are tested on flows from NMC publications, and three sources anchor this article:
- The NMC exam page for GLI06, Master or Mate Less Than 100 GRT, covering modules Q100 through Q352.
- The NMC Examination Guide for deck and engineering, reflecting regulations effective March 24, 2014.
- The NMC's Q352 document on Navigation and Deck General/Safety for raise-of-grade candidates.
This distinction is the single most common source of confusion for new candidates. A candidate on one route and a candidate on another may be assigned different modules, so two people can both be "studying for NM1GI" and still prepare for different content mixes.
Why Your Route Changes the Exam
The credential name includes both "GL" (Great Lakes) and "Inland," and the NMC's topic table distinguishes between them. Some topics apply specifically to Great Lakes service and are marked with a footnote in the NMC table. Two clusters carry that Great-Lakes-specific marking:
- Heavy weather operations and handling.
- Maneuvering for launching of lifeboats and liferafts in heavy weather.
If your approved route is Inland only, those topics may not apply to you the same way. If your route covers the Great Lakes, you should expect them. This is why it pays to confirm your route in writing before you build a study plan, and why the NM1GI requirements guide is worth reading alongside this one.
| Route Factor | What It Changes |
|---|---|
| Rules of the Road | Q100 (International and Inland) or Q300 (Inland) depending on approved route |
| Heavy-weather handling | Marked as Great-Lakes-specific in the NMC table |
| Lifeboat/liferaft launching in heavy weather | Marked as Great-Lakes-specific in the NMC table |
| Raise of grade | May involve Q352 as a separately listed module |
The Five Preparation Groups
The NMC does not publish official percentage weights for these modules, so any site claiming exact domain percentages is inventing them. What is published is the module and topic catalog. Organized for preparation, it forms five route-aware groups. The Rules choice (Q100 or Q300) counts as a single group, because you only prepare for the one assigned to your route.
- Rules of the Road: International and Inland (Q100) OR Inland (Q300), according to approved route.
- Deck General (Q347).
- Deck Safety (Q348).
- Navigation General: Great Lakes and Inland (Q349).
- Navigation Problems: Chart Plot (Q350).
These are unweighted preparation groups. They are not one common mandatory examination that every candidate takes in identical form. For a deeper walkthrough of each content area, see the complete guide to all five NM1GI content areas.
Rules of the Road: Choosing Q100 or Q300
Rules of the Road (Q100 or Q300)
The NMC lists three topic headings under this group: Watchkeeping, COLREGS, and Inland Navigational Rules. Which rules you are examined on depends on your approved route.
- Q100 covers International and Inland rules; Q300 covers Inland rules.
- Watchkeeping is listed here as well as in Deck Safety, so expect the subject to surface in both places.
- Know which rule set governs which waters, because applying the wrong one is the classic mistake.
Candidates often underestimate this module because the rules feel familiar from daily boating. The exam, however, tests precise application: right-of-way relationships, signals, lights, and responsibilities in specific encounter situations. Memorizing the general idea is not enough; you need to apply the right rule set to a described scenario.
Deck General (Q347): Seamanship and Ship Handling
Deck General is the broadest practical module, and the catalog shows why. It spans hands-on seamanship, vessel handling, and regulatory knowledge.
Seamanship and Marlinspike
Core seamanship, marlinspike seamanship, and purchases, blocks, and tackle form the traditional rope-and-rigging foundation.
- Know knots, splices, and line handling at a working level.
- Understand mechanical advantage in blocks and tackle.
Vessel Maneuvering and Handling
This is where Master-level judgment shows up. The catalog lists vessel handling in rivers and estuaries, maneuvering in shallow water, interaction with banks and passing ships, berthing and unberthing, anchoring and mooring, and dragging or clearing fouled anchors.
- Understand turn circle, pivot point, advance, and transfer.
- Know how bank effect and passing-ship interaction change handling.
- Be ready for wake reduction considerations.
- Heavy weather operations and lifeboat/liferaft launching maneuvers carry the Great-Lakes-specific marking.
Maritime Law and Shipboard Management
The general topics include national maritime law, credentialing of seamen, ship sanitation, vessel alteration, repair, and hot work, safety, ship's business, and the certificates and documents a vessel must carry.
- Learn which certificates and documents are required aboard.
- Understand the Master's responsibilities for training and shipboard management.
Deck Safety (Q348): Stability, Fire, and Emergencies
Deck Safety rewards candidates who think like a person responsible for lives aboard. The catalog groups its content into construction and stability, power plants, firefighting, emergency procedures, and communications.
Stability, Construction, and Damage Control
Principles of vessel construction, and trim and stability, underpin how a small vessel behaves when loaded, damaged, or caught in rough conditions.
- Understand how weight placement affects trim and stability.
- Connect stability knowledge to damage control decisions.
Fire Prevention and Firefighting
Topics include organization of fire drills, classes and chemistry of fire, firefighting systems, and basic firefighting and prevention.
- Match fire classes to appropriate extinguishing approaches.
- Know how a drill is organized and what the Master is responsible for.
Emergency Procedures
The emergency list is long and practical: collision, temporary repairs, passenger and crew safety in emergencies, fire or explosion, abandon ship procedures, rescuing survivors from a ship or aircraft in distress, man overboard procedures, and emergency towing.
- Know the sequence of actions for each emergency, not only the definitions.
- Small engine operation and maintenance also appears under vessel power plants.
Communications and signals, including storm, wreck, distress, and special signals, close out this module. Learn the meaning of each signal category rather than treating them as one blob of flags and sounds.
Navigation General (Q349) and Chart Plot (Q350)
The navigation side is split into a knowledge module and a practical plotting module. Candidates frequently find the plotting module the most demanding, which is a theme in the difficulty guide.
Navigation General: Great Lakes and Inland (Q349)
This module covers the theory and publications behind safe navigation:
- Navigation and position determination, including piloting, distance off, bearing problems, fix or running fix, chart navigation, and dead reckoning.
- Electronic navigation, instruments and accessories, and aids to navigation.
- Charts, navigation publications, and Notices to Mariners.
- Magnetic and gyro compasses, including magnetic compass principles, error and correction, and determination of compass error.
- Terrestrial observation.
- Meteorology and oceanography: weather system characteristics, weather charts and reports, and tides and tidal currents.
Navigation Problems: Chart Plot (Q350)
Chart plotting is retained as its own module. Its catalog overlaps heavily with the position-determination topics above, but here you must actually work problems: piloting, distance off, bearing problems, fix or running fix, chart navigation, dead reckoning, electronic navigation, instruments and accessories, aids to navigation, and charts and publications.
Where Q352 Fits for Raise of Grade
Q352, Navigation and Deck General/Safety, is listed as a separate raise-of-grade route module. It is not a sixth required section of the full original exam, and it is not a second Rules subject. If you are a first-time applicant for the original endorsement, your preparation centers on the five groups above. If you are raising the grade of an existing credential, your approval to test may assign Q352, and the NMC's Q352 document describes it.
Key Takeaway
Do not add Q352 to your study plan unless your approval to test assigns it. Preparing for modules you will not sit wastes time you need for Q350 plotting and the Rules.
Sequencing Your Preparation
Rather than a generic schedule, sequence by dependency. Navigation theory feeds chart plotting, and Deck General seamanship connects to Deck Safety emergencies. An example order that respects those links:
Rules of the Road
- Confirm whether your route uses Q100 or Q300 before starting.
- Learn the rule set that governs your waters first.
Navigation General (Q349)
- Build compass, charts, publications, and weather foundations.
Chart Plot (Q350)
- Drill fixes, running fixes, and dead reckoning on paper charts.
Deck General and Deck Safety
- Cover vessel handling, law, stability, firefighting, and emergencies.
- Add the Great-Lakes-specific heavy-weather topics only if they apply to your route.
For a broader planning framework, the NM1GI study guide expands on this, and you can test yourself on the NM1GI practice test site as you finish each block.
Where This Credential Gets Used
A Master or Mate endorsement for vessels under 100 GRT on Great Lakes and inland waters is a working credential for the operators of smaller commercial vessels. Typical settings include towing and barge work, small passenger and charter operations, harbor and fleeting work, and other commercial service on the lakes and rivers. Employers in these sectors look for a valid Coast Guard credential matched to the vessel and route, plus documented sea service.
Earnings and demand vary by region, vessel type, and employer, and this article does not quote figures, because none are published in the NMC sources it relies on. If you are weighing the investment, see the pages on NM1GI jobs, the salary analysis, and whether the certification is worth it.
Frequently Asked Questions
It is the National Master 100 GL and Inland credential, a U.S. Coast Guard National Maritime Center endorsement for Master or Mate of vessels under 100 GRT on the Great Lakes and inland waters, tracked under the NMC exam code GLI06.
Five route-aware preparation groups: Rules of the Road (Q100 or Q300), Deck General (Q347), Deck Safety (Q348), Navigation General (Q349), and Chart Plot (Q350). Your approval to test controls what you actually sit.
No. The Rules module is Q100 (International and Inland) or Q300 (Inland), depending on your approved route. It counts as one group in your preparation.
Q352, Navigation and Deck General/Safety, is a separately listed raise-of-grade module. It is not a sixth group in the full original exam and not a second Rules subject.
This page does not quote them because they should come from current NMC sources and your approval to test. See the guides on certification cost, passing score, and exam dates for what to verify, and the pass rate page for how to read any published outcomes.