Wheelhouse Prep USCG Mariner Exam Prep

Master or Mate < 200 GRT Rivers, Revision & Practice Exams

Master or Mate < 200 GRT Rivers. Built from official USCG NMC sample examinations (public domain).
Content last updated 12 June 2026

Revision Mode

Revise with instant feedback: the moment you pick an answer you see whether it was right, with the explanation where available. Untimed — ideal before you sit a mock exam. Questions you miss keep coming back until you know them.

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Exam Mode

Exam-day conditions: no feedback until you submit, each module scored separately so you can see your weak areas, plus an overall score against the pass mark, with a full question-by-question review at the end.

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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.

Modules & your progress

Unlock the full question bank

The free sample is 30 questions, spread across every module in the same proportions as the real exam. The full bank contains every question from the NMC's current published sample examinations for this credential, with written explanations on the popular small-vessel credentials, one-off $29, lifetime access on up to 3 devices, all credentials included.

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Score history

The real exam: key facts

Delivered byUS Coast Guard National Maritime Center; exams are sat at Coast Guard Regional Exam Centers (RECs)
Official examMerchant Mariner Credential (MMC) endorsement examinations
QuestionsSet per credential in your Approval to Test letter; the NMC does not publish module question counts
TimeEach module is sat in a 3½-hour examination period; modules are taken in consecutive periods
Passing scoreRules of the Road 90%; Deck General and Deck Safety 70% (NMC notice, January 2018)
Exam feeSet by 46 CFR 10.219: for an original officer endorsement, evaluation $100, examination $95 (lower level) or $110 (upper level), issuance $45
Pre-licensing or eligibilityApply to the Coast Guard first; you need the NMC's Approval to Test letter before you can book. The application stays valid for 12 months
Book your examdco.uscg.mil/nmc/Examinations

Checked 11 October 2026 from the official sources below. Rules and fees change, so confirm with US Coast Guard National Maritime Center; exams are sat at Coast Guard Regional Exam Centers (RECs) before you book.

Official sources

How Wheelhouse Prep compares

Wheelhouse is a $29 question bank built from the Coast Guard's own sample exams, not an approved course. Here is how it compares with the courses and tools mariners usually consider, including where they are the better choice. See the comparison with Mariners Learning System, Sea School, MPT and others.

Frequently asked questions

What score do I need to pass the Master or Mate < 200 GRT Rivers exam?

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

What modules are on the Master or Mate < 200 GRT Rivers exam?

The exam covers 2 modules: Deck General – Safety, Navigation General – Rivers.

How many practice questions are available for Master or Mate < 200 GRT Rivers?

This page includes free sample questions drawn from the official USCG sample examinations, with a full bank of around 116 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.

Do I need to create an account?

No. The free practice tests work in your browser with no signup. Your score history is saved on your own device.

When were these Master or Mate < 200 GRT Rivers questions last updated?

Last updated 12 June 2026. The bank is refreshed whenever the Coast Guard publishes revised sample examinations.

Sample Master or Mate < 200 GRT Rivers practice questions

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

A fire in electrical equipment should be extinguished by using which type of extinguishing agent?

  1. CO2 ✓
  2. Salt water
  3. Foam
  4. Low-velocity fog

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 ✓

As a warm front approaches how does barometric pressure change?

  1. Pressure falls ✓
  2. Pressure is steady
  3. Pressure rises
  4. Pressure is uncertain
Show all 30 sample questions with answers

What can be done to prevent small oil spills on deck from going overboard?

  1. Plugging the sounding pipes
  2. Plugging the drains and scuppers ✓
  3. Closing the lids on the vents
  4. Driving wooden plugs into the vents

Which U.S. agency assigns an official number to a vessel?

  1. Collector of Customs
  2. Treasury Department
  3. Coast Guard ✓
  4. American Bureau of Shipping

What is the purpose of a striking plate?

  1. It provides a surface for applying force on machinery
  2. It prevents valve stem over-travel
  3. It provides a landing surface for the sounding bob ✓
  4. It absorbs machinery vibration

Safe water buoys may show ONLY which type of light?

  1. flashing green lights
  2. yellow lights
  3. white lights ✓
  4. flashing red lights

Which is TRUE of echo-sounders?

  1. They measure the average depth from waterline to hard bottom
  2. They measure the actual depth of water below keel ✓
  3. They measure the actual depth of water
  4. They measure the average depth of water to soft bottom

Advection fog is most commonly caused by __________.

  1. warm moist air being blown over a colder surface ✓
  2. saturation of cold air by rain
  3. air being warmed above the dew point
  4. a rapid cooling of the air near the surface of the Earth at night

Which statement is TRUE concerning River currents?

  1. A current will hug the inside of a bend
  2. Currents cause the greatest depth of water on the outside of a bend ✓
  3. The currents pick up speed where the channel widens
  4. The currents run slower in the center of the channel as opposed to the sides

Which mooring line has the most elastic elongation?

  1. Dacron
  2. Manila
  3. Nylon ✓
  4. Polypropylene

For small angles of inclination, if the KG were equal to the KM, which is TRUE concerning the vessel?

  1. The vessel possesses neutral stability ✓
  2. The vessel possesses positive stability
  3. The vessel possesses maximum stability
  4. The vessel possesses negative stability

How are buoys which mark isolated dangers painted?

  1. Alternating green and black bands
  2. Alternating red and black bands ✓
  3. Alternating green and white bands
  4. Alternating red and white stripes

On a small boat, if someone fell overboard and you did not know over which side the person fell, which action should you take?

  1. Immediately reverse the engines
  2. Increase speed to full to get the vessel away from the person
  3. First put the rudder hard over in either direction
  4. Stop the propellers from turning and throw a ring buoy over the side ✓

When cleaning up an oil spill in U.S. waters you must obtain the approval of the Federal On-Scene Coordinator before using which of the following?

  1. Skimmers
  2. Straw
  3. Chemical agents ✓
  4. Sawdust

A sylphon cell is a part of which instrument?

  1. A barograph ✓
  2. A thermograph
  3. A maximum thermometer
  4. A hygrometer

In general, how often are sanitary inspections of passenger and crew quarters made aboard passenger vessels in river service?

  1. Once each day
  2. Once each week
  3. Once each month ✓
  4. Once each trip

The dry bulb temperature is 78oF and the wet bulb temperature is 62oF. What is the relative humidity?

  1. 16%
  2. 24%
  3. 39% ✓
  4. 79%

If you observe a rapid fall of barometric pressure, which action should you take?

  1. Call the Coast Guard to verify the change
  2. Contact the NWS or a local radio station
  3. Know that the barometer is not working properly
  4. Prepare for an onset of stormy weather with strong winds ✓

Under the U.S. Aids to Navigation System on the Western Rivers, which is TRUE of a preferred channel buoy?

  1. It shall be solid red
  2. It shall be horizontally-banded red and green ✓
  3. It shall be vertically-striped red and white
  4. It shall be solid green

The Coast Guard Captain of the Port has excluded all traffic from a section of a port, while a regatta is taking place. Which describes the buoys marking this exclusion area?

  1. A nun- or can-shaped to conform to the overall direction of navigation
  2. An orange and white can ✓
  3. Marked with a spherical topmark
  4. A yellow can

When shall an Operator of an Uninspected Passenger Vessel be required to produce his/her MMC?

  1. Immediately, when requested by a USCG boarding officer ✓
  2. Only when the vessel has at least 6 passengers for hire and requested by a USCG boarding officer
  3. Only when the vessel is involved in a marine accident
  4. An Operator of an Uninspected Passenger Vessel is not required to carry his/her MMC

You are picking up a conscious person that has fallen overboard in one of the vessels motor boats. Recovery is easier in a light breeze if you approach from which direction?

  1. Leeward with the victim to windward
  2. Approach with the wind on your starboard side
  3. Windward with the victim to leeward ✓
  4. Approach with the wind on your port side

A mariner whose credential has been revoked shall not be issued another credential without which of the following?

  1. Approval of the Commandant ✓
  2. Approval of the Officer-in-Charge, Marine Inspection
  3. Approval of an administrative law judge
  4. Taking a new examination

You are picking up an unconscious person that has fallen overboard in a fresh breeze. For safety reasons how should a small craft approach?

  1. With the victim to leeward
  2. With the wind on your port side
  3. With the wind on your starboard side
  4. With the victim to windward ✓

In illustration D044DG below, what is the mooring line labeled "F" called?

  1. Forward spring line
  2. Bow breast line ✓
  3. Bow line
  4. Bow shore line

If ignited, which material would be a class B fire?

  1. Paper
  2. Diesel Oil ✓
  3. Magnesium
  4. Wood

In relation to cargo gear, what does "SWL" mean?

  1. Ship's working lift
  2. Safe working load ✓
  3. Starboard wing lift
  4. Stress, weight, load

The place where a channel moves from along one bank of the river over to the other bank of the river is known by which term?

  1. Cutoff
  2. Draw
  3. Draft
  4. Crossing ✓

The magnetic compass magnets are acted on by the horizontal component of the Earth's total magnetic force. Where is this magnetic force the GREATEST?

  1. At the north magnetic pole
  2. At the south magnetic pole
  3. At the magnetic prime vertical meridian
  4. At the magnetic equator ✓