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Second/Third Mate of Unlimited Tonnage, Revision & Practice Exams

Second/Third Mate of Unlimited Tonnage. Built from official USCG NMC sample examinations (public domain).
Content last updated 12 June 2026

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The real exam is passed module by module: Rules of the Road requires 90%, most other modules 70%. Chart-plotting modules are taken on paper and not included.

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Frequently asked questions

What score do I need to pass the Second/Third Mate of Unlimited Tonnage exam?

You must pass each module separately. Most modules require 70% to pass.

What modules are on the Second/Third Mate of Unlimited Tonnage exam?

The exam covers 4 modules: Deck General, Deck Safety, Navigation General – Near Coastal, Navigation General – Oceans.

How many practice questions are available for Second/Third Mate of Unlimited Tonnage?

This page includes free sample questions drawn from the official USCG sample examinations, with a full bank of around 262 questions across all modules available with lifetime access.

Are these real USCG exam questions?

Every question comes from the U.S. Coast Guard National Maritime Center's published sample examinations, which are U.S. government works in the public domain. Wheelhouse Prep is not affiliated with or endorsed by the U.S. Coast Guard.

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Sample Second/Third Mate of Unlimited Tonnage practice questions

A selection of free questions from the official USCG sample examinations. Use the interactive modules above for timed, scored drills.

How long must a "Declaration of Inspection" be kept on board?

  1. One week
  2. Two weeks
  3. One month ✓
  4. Three months

Which international body is responsible for drafting the MARPOL convention prohibiting marine pollution?

  1. The Maritime Advisory Council
  2. The International Maritime Organization ✓
  3. The Association of Seafaring Nations
  4. The International Association of Shipping

What best describes for how long a gas-free test is good?

  1. For the instant that it is made ✓
  2. Until valves in line with the tank or compartment are reopened
  3. Until changes in temperature or pressure affect the vapor content in the space
  4. For as long as is indicated on the gas-free certificate
Show all 40 sample questions with answers & explanations

What is NOT required as special safety equipment on a tankship carrying hazardous cargoes in bulk?

  1. Shower and eyewash fountain
  2. Two portable vapor detectors suitable for the cargoes carried ✓
  3. Equipment to lift an injured person from a pumproom
  4. A safety locker adjacent to the emergency shutdown station

Which statement is TRUE concerning a motor lifeboat?

  1. It is propelled by engine or hand-propelling gear.
  2. It must be able to maintain a loaded speed of 6 knots. ✓
  3. It has a sufficient fuel capacity, if motorized, for 48 hours of operation.
  4. All of the above

A vessel's bottom will be subjected to tension when weight is concentrated in which location(s)?

  1. Aft
  2. Amidships ✓
  3. Forward
  4. At both ends of the vessel

Which is TRUE of a distress signal?

  1. It shall consist of 5 or more short blasts of the fog signal apparatus
  2. It shall consist of the raising and lowering of a large white flag
  3. It is used to indicate doubt about another vessel's intentions
  4. It may be used individually or in conjunction with other distress signals ✓

A situation has occurred where it becomes necessary for you to be towed. What action should be taken to prevent your vessel from yawing?

  1. Shift weight to the center of the boat
  2. Shift weight to the bow
  3. Throw excess weight overboard
  4. Shift weight to the stern ✓

Why: Shifting weight aft sets the stern deeper, increasing drag aft so the towed vessel trails straight behind the towline like a weathervane instead of sheering from side to side.

How should latitude 54°18.9'N be written when preparing an AMVER report?

  1. 0543N
  2. 5419N ✓
  3. 54.3N
  4. 54°N

The SS AMERICAN MARINER has drafts of: FWD 28'-00", AFT 30'-04". Use the white pages of the Stability Data Reference Book to determine the drafts if you ballast the forepeak with 110.8 tons of seawater.

  1. FWD 28'-08.2", AFT 29'-11.6"
  2. FWD 28'-09.0", AFT 29' 11.0"
  3. FWD 28'-09.8", AFT 29' 10.4" ✓
  4. FWD 28'-10.6", AFT 29' 09.8"

How are chart legends which indicate a conspicuous landmark printed?

  1. In italics
  2. With underlined letters
  3. In boldfaced print
  4. In capital letters ✓

What is the purpose of the "reference hand" on an aneroid barometer?

  1. To adjust the barometer
  2. To indicate any change in the reading of the barometer ✓
  3. To provide a correction for height above sea level
  4. To provide a correction for temperature changes

You take a bearing of 176° of a lighthouse. Which bearing of another object would give the best fix?

  1. 079° ✓
  2. 151°
  3. 176°
  4. 292°

Which is the reference datum used in determining the heights of land features on most charts?

  1. Mean low water
  2. Half-tide level
  3. Mean sea level
  4. Mean high water ✓

Which term is given to the mechanical lifting of air by the upslope slant of the terrain?

  1. Vertical lifting
  2. Convective lifting
  3. Topographic lifting ✓
  4. Advective lifting

At 0000 you fix your position and plot a new DR track line. At 0200 you again fix your position, and it is 0.5 mile east of your DR. Which statement is TRUE?

  1. The current is westerly at 0.5 knot.
  2. The current cannot be determined.
  3. The drift is 0.25 knot. ✓
  4. You must increase speed to compensate for the current.

Your vessel is on course 150°T, speed 17 knots. The apparent wind is from 40° off the starboard bow, speed 15 knots. What is the speed of the true wind?

  1. 9.0 knots
  2. 10.2 knots
  3. 11.0 knots ✓
  4. 12.0 knots

When trying to sight a lighthouse you notice a glare from a town in the background. How does this affect the range at which the light may be sighted?

  1. Increased if the light is red or green due to contrast with the glare
  2. Considerably reduced and difficult to distinguish ✓
  3. Unchanged
  4. Increased slightly due to extra lighting

The new Moon cannot be seen because the Moon is __________.

  1. In the opposite direction of the Sun
  2. Below the horizon
  3. Between the Earth and the Sun ✓
  4. At quadrature

You are plotting a running fix. The LOP to be run forward is an arc from a radar range, what technique should be used?

  1. The distance between LOP's should be added to the radar range and a new arc swung.
  2. The arc should be converted into a straight line using offsets and then run forward.
  3. An arc should never be run forward.
  4. The position of the object observed should be advanced to the new time and a new arc swung using the radius of the old arc. ✓

What must the owner or Master do if any of the towing vessel's required navigational safety equipment fails during a voyage?

  1. Repair it at the earliest practicable time
  2. Enter its failure in the log or other on-board record
  3. Consider the state of the equipment in deciding whether it is safe for the vessel to proceed
  4. All of the above ✓

At about GMT 1436, on 3 December, the lower limb of the Moon is observed with a sextant having an index error of 2.5' on the arc. The height of eye is 32 feet. The sextant altitude (hs) is 3°38.8'. What is the observed altitude?

  1. Ho 4°18.6'
  2. Ho 4°29.1' ✓
  3. Ho 4°36.3'
  4. Ho 4°42.2'

Under the IALA-A Buoyage System, a buoy indicating the preferred channel is to port would have __________.

  1. a pillar shape
  2. horizontal bands ✓
  3. an even number
  4. an odd number

Which theoretical minimum number of measurements from satellites does a GPS receiver need in order to provide an exact three-dimensional position?

  1. Five
  2. Four ✓
  3. Three
  4. Two

You are underway in heavy weather and your bow is into the seas. Which action should you take to prevent pounding?

  1. Secure all loose gear on your vessel
  2. Increase the speed of the vessel
  3. Decrease the speed of the vessel ✓
  4. Put the seas on a 85-degree angle from the bow

If your propeller is racing in rough weather, which action should you take?

  1. Stop your engine until the rough weather passes
  2. Ignore it, this is acceptable in rough weather
  3. Decrease your engine speed ✓
  4. Increase your engine speed

Why: Racing happens when pitching lifts the propeller near or out of the water, letting it overspeed and shock-load the shaft and engine. Reducing engine speed limits the overspeeding while keeping steerageway, unlike stopping entirely.

When the period of beam seas equals the natural rolling period of a vessel, what will most likely occur?

  1. Excessive rolling ✓
  2. Excessive yawing
  3. Excessive pitching
  4. No change should be evident

Which term describes the distance a vessel moves in the direction of the original course from the point where the rudder is put over to any point on the turning circle?

  1. Pivoting point
  2. Transfer
  3. Advance ✓
  4. Drift angle

Why is a VLCC (100,000 DWT+) with a 30,000 Shaft Horsepower Steam Turbine slow to respond to engine movements, and has less stopping power than normal ships?

  1. They have a bigger propeller
  2. They have smaller power to weight ratio ✓
  3. They have larger power to weight ratio
  4. They possess smaller propellers

Why: A loaded VLCC has enormous displacement but comparatively modest horsepower, a small power-to-weight ratio, so the engine has little leverage over the ship's huge momentum, making her slow to respond and hard to stop.

Which states the requirements for the access to a cargo pumproom in a tank vessel carrying grades C or D liquid cargo?

  1. The pumproom access shall only be from enclosed areas free from sources of vapor ignition
  2. The pumproom access shall be from within the vessel
  3. The pumproom access shall be from areas equipped with power ventilation
  4. The pumproom access shall be from the open deck ✓

Why: Regulations require pumproom access on these tankships to be from the open deck, so personnel never pass through enclosed spaces where cargo vapors could accumulate and escape or rescue is direct.

Great Lakes vessels, using liferafts, must have sufficient liferaft capacity on each side of the vessel to accommodate how many persons onboard?

  1. 50% of the persons on board
  2. 100% of the persons on board ✓
  3. 150% of the crew
  4. 100% of the persons normally assigned to those spaces

According to the Lifesaving regulations in Subchapter W, fire and abandon ship drills must be held within 24 hours of leaving port if the percentage of the crew that has not participated in drills aboard that particular vessel in the prior month exceeds which percentage?

  1. 5%
  2. 10%
  3. 25% ✓
  4. 40%

Why: Subchapter W requires fire and abandon-ship drills within 24 hours of leaving port whenever more than 25 percent of the crew did not participate in drills aboard that vessel during the previous month.

What should you do if you have transmitted a distress call a number of times on channel 16 and have received no reply?

  1. Turn up the volume on the receiver before transmitting again.
  2. Repeat the message using any other channel on which you might attract attention. ✓
  3. Key the microphone several times before transmitting again.
  4. Report the problem to the head electrician.

You are calling another vessel by radiotelephone using the International Code of Signals. He responds with the words "Alpha Sierra". What does this indicate?

  1. You should send your message in plain language
  2. You should proceed with your message
  3. He cannot accept traffic immediately ✓
  4. You should send your message in International Code

Which fog is produced by warm moist air passing over a cold surface?

  1. Conduction fog
  2. Frontal fog
  3. Radiation fog
  4. Advection fog ✓

Buoys which only mark the left or right side of the channel will never exhibit a light with which characteristic?

  1. Quick flashing
  2. Equal interval (isophase)
  3. Composite group flashing ✓
  4. Flashing

In which country would you expect the channels to be marked with the IALA-B Buoyage System?

  1. Peru ✓
  2. Poland
  3. Saudi Arabia
  4. Morocco

How is an occluded front represented on a weather map?

  1. A dashed blue line
  2. An alternate red and blue line
  3. A blue line
  4. A purple line ✓

If a weather bulletin shows the center of a low-pressure system to be 100 miles due east of you, what winds can you expect in the Southern Hemisphere?

  1. North-northeasterly
  2. South-southwesterly ✓
  3. South-southeasterly
  4. North-northwesterly

An orange and white buoy with a rectangle on it displays what information?

  1. distances
  2. directions
  3. locations
  4. All of the above ✓