Wheelhouse Prep USCG Mariner Exam Prep

Master < 100 GRT to Master or Mate < 200 GRT Great Lakes and Inland, Revision & Practice Exams

Master < 100 GRT to Master or Mate < 200 GRT Great Lakes and Inland. 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.

Modules to include
Number of questions

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.

Modules to include
Exam length
Timer (optional)

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 12 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.

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

Frequently asked questions

What score do I need to pass the Master < 100 GRT to Master or Mate < 200 GRT Great Lakes and Inland exam?

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

What modules are on the Master < 100 GRT to Master or Mate < 200 GRT Great Lakes and Inland exam?

The exam covers 1 module: Navigation and Deck General – Safety.

How many practice questions are available for Master < 100 GRT to Master or Mate < 200 GRT Great Lakes and Inland?

This page includes free sample questions drawn from the official USCG sample examinations, with a full bank of around 46 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 < 100 GRT to Master or Mate < 200 GRT Great Lakes and Inland questions last updated?

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

Sample Master < 100 GRT to Master or Mate < 200 GRT Great Lakes and Inland practice questions

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

Regulations require that prior to departure on a three-day voyage, the steering gear, whistle, and communications system between the bridge and engine room must be tested prior to departure no earlier than __________.

  1. 1 hour
  2. 4 hours
  3. 8 hours
  4. 12 hours ✓

What quality of a diesel fuel is most significant for efficient combustion?

  1. Volatility ✓
  2. Flash point
  3. Specific heat
  4. Viscosity

On an inspected vessel, when may a stability test be dispensed with?

  1. Coast Guard does not have a qualified inspector available
  2. Coast Guard has the approved stability test results of a sister vessel ✓
  3. The projected cost is unreasonable
  4. The vessel is of a proven design
Show all 12 sample questions with answers

Which agency must approve the safety equipment on board inspected vessels?

  1. The U.S. Coast Guard ✓
  2. The Occupational Safety and Health Administration (OSHA)
  3. The Safety Standards Bureau
  4. The National Safety Council

What is the reaction of a gyrocompass to an applied force known as?

  1. Earth rate
  2. Precession ✓
  3. Gyroscopic inertia
  4. Gravity effect

Regulations require that cargo pumprooms handling grades D and/or E liquid cargo only shall be fitted with ducts extended to the weather deck. How many ducts are required?

  1. 1
  2. 2 ✓
  3. 3
  4. 4

All marine low-speed diesels are of what design?

  1. Two-stroke ✓
  2. Forced exhaust
  3. Electronic ignition
  4. Four-stroke

Which statement is TRUE concerning CO2 cylinders which protect the small space in which they are stored?

  1. The cylinders can NOT contain more than 200 pounds of CO2
  2. The cylinders shall have an audible alarm
  3. The cylinder shall be automatically operated by a heat actuator ✓
  4. All of the above

In reference to accidental oil pollution, the most critical time during bunkering is when __________.

  1. Final topping off is occurring ✓
  2. Hoses are being disconnected
  3. You first start to receive fuel
  4. Hoses are being blown down

What are the three most common basic types of diesel engine starters?

  1. Metered, hydraulic, automatic
  2. Air, emergency, hydraulic
  3. Air, water, electric
  4. Air, hydraulic, electric ✓

In illustration D041DG below, which of the following is the symbol for the reference from which transverse measurements are made?

  1. 5 ✓
  2. 4
  3. 3
  4. 1

By regulation, cargo tank atmosphere must be inert before and during which operation?

  1. crude oil washing
  2. stripping
  3. topping off
  4. All of the above ✓