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Key Facts: USCG Master Unlimited Exam

ONC01

NMC Exam Code

USCG National Maritime Center

~330 questions

Oceans Module Battery

USCG NMC ONC01

90%

Rules of the Road Pass Mark

USCG NMC Q100

70%

Most Module Pass Mark

USCG NMC ONC01

46 CFR 11.404

Master Service Requirement

Code of Federal Regulations

5 years

Credential Validity

USCG Merchant Mariner Credential

The USCG Master / Chief Mate of Unlimited Tonnage exam (NMC ONC01) is the highest U.S. national deck license test, taken by merchant marine officers qualifying under 46 CFR 11.404. The oceans battery runs roughly eight modules totaling about 330 questions: Q100 Rules of the Road (50 questions, 90% to pass), Q101 and Q102 Deck General (50 each, 70%), Q103 Deck Safety (70, 70%), Q104 Deck Safety Stability Problems (15, 70%), Q106 Navigation General Oceans (70, 70%), Q107 Chart Plot (10, 90%), and Q108 or Q109 Navigation Problems. Content spans the COLREGS and Inland Rules; shiphandling, anchoring, cargo stowage and securing, maritime law and ship's business; ship construction, damage control, firefighting and lifesaving; stability and trim including GM, free surface, and loll; and navigation general plus problems in sailings, tides, current, and celestial sights. A Chief Mate endorsement raises to Master without a further professional exam.

Sample USCG Master Unlimited Practice Questions

Try these sample questions to review concepts for the USCG Master Unlimited exam. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1Under the International Rules (COLREGS), what does a power-driven vessel underway exhibit at night when not constrained or restricted in any special way?

A.Sidelights and a sternlight only

B.An all-round white light and sidelights

C.Masthead light(s), sidelights, and a sternlight

D.Two all-round red lights in a vertical line

Explanation: Rule 23 requires a power-driven vessel underway to show a forward masthead light, sidelights, and a sternlight (vessels 50 m or more must also show a second, after masthead light higher than the forward one).

2Two power-driven vessels are meeting head-on at night. Under the International Rules, what is each vessel required to do?

A.Both vessels shall stop their engines until the situation is resolved

B.Each shall alter course to port and pass starboard to starboard

C.The vessel to the other's starboard side shall hold course and speed

D.Each shall alter course to starboard and pass port to port

Explanation: Rule 14 states that when two power-driven vessels meet head-on so as to involve risk of collision, each shall alter course to starboard so that each passes on the port side of the other.

3Under the International Rules, in a crossing situation between two power-driven vessels where risk of collision exists, which vessel is the give-way vessel?

A.The vessel that has the other on her own port side

B.The faster of the two vessels regardless of bearing

C.The vessel that has the other on her own starboard side

D.The vessel with the greater draft

Explanation: Rule 15 makes the vessel that has the other on her own starboard side the give-way vessel; she shall keep out of the way and, if circumstances permit, avoid crossing ahead of the other vessel.

4Under the International Rules, a vessel constrained by her draft may, in addition to her normal lights for a power-driven vessel, exhibit which signal?

A.A black diamond shape by day only

B.Two all-round red lights in a vertical line, or a ball by day

C.An all-round red light over an all-round white light

D.Three all-round red lights in a vertical line, or a cylinder by day

Explanation: Rule 28 provides that a vessel constrained by her draught may exhibit three all-round red lights in a vertical line, or a cylinder by day, in addition to the lights prescribed for a power-driven vessel in Rule 23.

5Under the International Rules, what sound signal must a power-driven vessel make in or near an area of restricted visibility when making way through the water?

A.One short blast at intervals of not more than 2 minutes

B.Two prolonged blasts at intervals of not more than 2 minutes

C.One prolonged blast at intervals of not more than 2 minutes

D.Three short blasts at intervals of not more than 1 minute

Explanation: Rule 35(a) requires a power-driven vessel making way through the water to sound one prolonged blast at intervals of not more than 2 minutes.

6Under the Inland Navigation Rules, when two power-driven vessels are crossing and the give-way vessel intends to pass astern of the stand-on vessel, what whistle signal exchange initiates the maneuver?

A.The give-way vessel sounds one short blast; agreement is one short blast in reply

B.The give-way vessel sounds five short and rapid blasts

C.The give-way vessel sounds two short blasts; agreement is two short blasts in reply

D.No whistle signal is exchanged; the rule operates silently

Explanation: Under Inland Rule 34, a proposed maneuver to leave the other vessel on the proposing vessel's port side (passing astern in this crossing) is signaled by two short blasts, with agreement indicated by two short blasts in reply.

7Under both the International and Inland Rules, which statement about the overtaking situation is correct?

A.An overtaking vessel becomes the stand-on vessel once abeam of the other vessel

B.Any subsequent alteration of bearing between the two vessels relieves the overtaking vessel of her duty to keep clear

C.The overtaking vessel must keep out of the way until finally past and clear

D.A vessel is overtaking when approaching from more than 22.5 degrees forward of the other vessel's beam

Explanation: Rule 13 provides that an overtaking vessel shall keep out of the way of the vessel being overtaken, and this duty continues until she is finally past and clear.

8Under the International Rules, a vessel at anchor of 100 meters or more in length is required to do what regarding her lights?

A.Show a single all-round white light forward only

B.Show two all-round red lights in a vertical line

C.Show all-round white lights forward and near the stern, and use working or equivalent lights to illuminate her decks

D.Show sidelights and a sternlight as if underway

Explanation: Rule 30 requires a vessel at anchor to show an all-round white light forward and one at or near the stern; vessels of 100 m or more shall also use available working lights to illuminate their decks.

9Under the International Rules, a vessel engaged in towing where the length of the tow exceeds 200 meters shall exhibit what additional day signal?

A.A black ball where it can best be seen

B.A cylinder where it can best be seen

C.A diamond shape where it can best be seen

D.Two black balls in a vertical line

Explanation: Rule 24(a) requires a vessel towing, when the length of the tow exceeds 200 m, to exhibit a diamond shape where it can best be seen (and three masthead lights in a vertical line at night).

10Under the International Rules, when a vessel is in doubt whether a close-quarters situation is developing or risk of collision exists, she shall:

A.Sound the danger signal and stop

B.Maintain course and speed and continue observing

C.Immediately make a substantial alteration to port

D.Assume risk of collision exists and act accordingly

Explanation: Rule 7(a) provides that if there is any doubt, such risk shall be deemed to exist; the mariner must err on the side of caution and act as though collision risk is present.

About the USCG Master Unlimited Exam

The USCG Master / Chief Mate of Unlimited Tonnage examination (NMC exam code ONC01) is the top-level U.S. national deck-officer license examination for ocean or near-coastal self-propelled vessels of unlimited tonnage. It is taken by experienced merchant marine officers who meet the sea-service requirements of 46 CFR 11.404 (Master) and 11.407/11.305 for the officer-of-the-watch path, and a Chief Mate endorsement raises to Master without a further professional exam under 46 CFR 11.903(c)(1). The exam is a modular battery covering Rules of the Road, deck general, deck safety, stability, navigation general, and navigation problems.

Exam sponsor: U.S. Coast Guard National Maritime Center (NMC). The requirements and fees below concern the certification or admission exam, separate from our free practice resources.

Assessment

Question count not published by the exam provider

Time Limit

Several hours per module per the NMC exam schedule

Passing Score

70% on most modules; 90% on Rules of the Road and chart-plot modules

Exam / Certification Fees

Evaluation and credentialing fees apply per the MMC application (confirm on NMC)

Exam sponsor website

Fees, eligibility, and exam policies can change. Confirm them with the exam sponsor before applying or paying.

Official sources

Our practice resources: topics covered

We aim to reflect publicly available exam outlines and topic information in our study resources. Coverage, format, and difficulty may differ from the actual exam, and we cannot guarantee that every detail is accurate or current. Confirm exam requirements, fees, and policies with the official exam sponsor.

20%

Rules of the Road (COLREGS & Inland)

Steering and sailing rules, the head-on, crossing, and overtaking situations, lights and shapes for each vessel type, sound and maneuvering signals, the five-short-blast danger signal, restricted-visibility fog signals, narrow channels and Western Rivers, and the responsibilities-between-vessels hierarchy (90% required to pass)

24%

Deck General

Shiphandling including pivot point, transverse thrust on a single right-hand screw, turning circle and tactical diameter, squat and interaction, anchoring and shots of chain and scope, cargo stowage and securing and stowage factor, dunnage and ventilation, maritime law, bills of lading and general average, ship's business and the certificate of inspection, and ship construction

20%

Deck Safety

The fire triangle and fire classes A through D, fixed CO2 flooding precautions, lifesaving appliances, liferafts and hydrostatic release units, immersion suits, GMDSS EPIRB and radar SART, the muster list and SOLAS drill requirements, watertight integrity and subdivision, man-overboard turns, and emergency procedures

10%

Stability

Metacentric height (GM) and the relationship of G and M, negative GM and the angle of loll and its correction, free surface effect and minimizing slack tanks, the curve of static stability and angle of vanishing stability, reserve buoyancy and freeboard, counter-flooding cautions, and damage-control stability problems

16%

Navigation General

Variation, deviation, and compass error; the nautical mile; sextant altitude corrections and refraction greatest near the horizon; amplitude and meridian altitude observations; Mercator rhumb lines and great-circle distance; radar range and bearing resolution and plotting; meteorology including Buys Ballot's Law and barometric trends; and electronic navigation

10%

Navigation Problems & Chart Plot

Time-speed-distance, set and drift and current-sailing triangles, course to steer, tides and tide-table secondary stations and chart datum, celestial sight reduction and the altitude intercept, lines of position, running fixes from two bearings of one object, and chart plotting (90% required on the chart-plot module)

Preparing for the USCG Master Unlimited Exam

What You Need to Know

Passing score: 70% on most modules; 90% on Rules of the Road and chart-plot modules
Assessment: Question count not published by the exam provider
Time limit: Several hours per module per the NMC exam schedule
Exam / certification fees: Evaluation and credentialing fees apply per the MMC application (confirm on NMC) Official sources

Using Our Practice Resources

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USCG Master Unlimited: Suggested Study Strategy

1Drill Rules of the Road to mastery: you must score 90%, so memorize the lights and shapes (Rule 23-31), the head-on/crossing/overtaking actions (Rules 13-15), and the fog signals at intervals of not more than 2 minutes (Rule 35)

2Know the stability fundamentals cold: GM as the distance between G and the metacenter, the virtual rise in G from free surface effect, and correcting an angle of loll by lowering G with low ballast rather than pressing up high side tanks

3Memorize anchoring numbers: a shot of chain is 15 fathoms (90 feet) and good holding generally needs a scope of about 5:1 to 7:1 of chain length to water depth

4For deck safety, learn the fire classes A-D (Class C is energized electrical), the seven-or-more-short-then-one-prolonged general alarm, monthly SOLAS fire and abandon-ship drills, and that a 406 MHz EPIRB alerts via satellite while a radar SART replies to X-band radar

5In navigation general, remember refraction is greatest near the horizon, an amplitude is observed on the celestial horizon for compass error, and a meridian altitude at local apparent noon gives latitude

6Practice navigation problems with worksheets: time-speed-distance, set-and-drift triangles, tide-table secondary stations, and celestial sight reduction laying the altitude intercept (Ho minus Hc) perpendicular to the body's azimuth

Frequently Asked Questions

What is the USCG Master / Chief Mate Unlimited Tonnage exam?

It is the top-level U.S. national deck-officer license examination (NMC exam code ONC01) for ocean or near-coastal self-propelled vessels of unlimited tonnage, taken by experienced merchant marine officers who meet the sea-service requirements of 46 CFR 11.404.

How many questions are on the exam and what are the passing scores?

The oceans battery is a modular set of about eight modules totaling roughly 330 questions. Most modules require 70% to pass, but Rules of the Road and the chart-plot module require 90%, and the oceans navigation-problems module requires 80%.

What subjects are tested?

The modules cover Rules of the Road (COLREGS and Inland), deck general (shiphandling, anchoring, cargo, maritime law, ship's business), deck safety (stability, firefighting, lifesaving, damage control), navigation general (terrestrial, celestial, meteorology, electronic), and navigation problems including chart plot.

Do I have to retake the exam to go from Chief Mate to Master?

No. Under 46 CFR 11.903(c)(1) a Chief Mate of unlimited tonnage endorsement raises to Master of unlimited tonnage without a further professional examination once the required sea service is met.

How is this different from the Master 1600 GRT exam?

Master 1600 GRT is a tonnage-limited license examined under a different NMC module battery (exam code ONC03). The unlimited-tonnage exam (ONC01) is broader and more demanding, with no upper tonnage limit on the resulting endorsement.

Is the exam multiple choice?

Most modules are multiple choice. The chart-plot and navigation-problems modules also require plotting and computation work (sailings, set and drift, tides, and celestial sight reduction) carried out on charts and worksheets.

Free Practice Questions for USCG Master Unlimited

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