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USCG Motor Plants Practice Test

492 Motor Plants questions from 12 of the National Maritime Center’s published sample exams, each with the NMC’s answer key. Questions that need an illustration, a chart or a reference book are left out.

140 of them come with the closest regulation or reference section, shown with the answer.

Take a quiz of 10 drawn at random, or read the 10 sample questions and answers below.

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10 sample Motor Plants questions with answers

The same 10 on every visit. A related section is the closest match RegKnot found in the regulations and references; it is not part of the NMC’s answer key.

Question 1 · Third Assistant Engineer
Which of the following actions takes place in the control circuit of an automatically fired auxiliary boiler when the desired steam pressure is obtained?
- A.A temperature sensing device opens the circuit breaker in the burner motor.
- B.The stack relay actuates the low limit control which breaks the ignition circuit.
- C.The high limit control secures power to the entire oil firing system. (correct answer)
- D.The stack relay secures power to the high voltage side of the ignition transformer.
Answer: C. The high limit control secures power to the entire oil firing system.
Related regulation: NVIC 01-69 Encl.1 — Automated Main and Auxiliary Machinery — Enclosure (1)
Question 2 · UFIV – Assistant Engineer
Assuming the use of ultra-low sulfur content diesel fuel, what combination of conditions associated with uninspected fishing industry vessel engine room operations would require the most frequent draining of exhaust systems of condensation?
- A.Winter operations with lengthy ship escort transit times.
- B.Winter operations with prolonged idling on station. (correct answer)
- C.Summer operations with prolonged idling on station.
- D.Summer operations with lengthy ship escort transit times.
Answer: B. Winter operations with prolonged idling on station.
Related regulation: NVIC 05-86 Encl.1 — Voluntary Standards for U.S. Uninspected Commercial Fishing Vessels — Enclosure (1)
Question 3 · OSV – Chief Engineer
Due to the questionable mineral content of fresh water taken on from shore as a source of make-up water for diesel engine closed, recirculating cooling water systems, besides chemical treatment and coolant testing, what is the best line of defense in minimizing cooling system problems?
- A.Maintaining a tight system and promptly repairing leaks (correct answer)
- B.Increasing the frequency of draining, flushing, and re-filling the system
- C.Maintaining cooling water temperatures at lower-than-normal values
- D.Maintaining cooling water temperatures at higher-than-normal values
Answer: A. Maintaining a tight system and promptly repairing leaks
Related regulation: NVIC 05-86 Encl.1 — Voluntary Standards for U.S. Uninspected Commercial Fishing Vessels — Enclosure (1)
Question 4 · Assistant Engineer – Limited
The primary function of a flame safeguard system, as used on an automatically fired auxiliary boiler, is to prevent what condition?
- A.Accidental dry firing and overpressure
- B.Uncontrolled fires in the furnace
- C.Explosions in the boiler furnace (correct answer)
- D.Overheating of the pressure parts
Answer: C. Explosions in the boiler furnace
Related regulation: NVIC 01-69 Encl.1 — Automated Main and Auxiliary Machinery — Enclosure (1)
Question 5 · Chief Engineer – Limited
Burner ignition failure in an automatically fired auxiliary boiler would be caused by __________.
- A.a burned-out solenoid in the oil supply valve (correct answer)
- B.high temperature excess air
- C.incorrectly setting the hotwell dump valve
- D.an incorrectly positioned burner snubber relay
Answer: A. a burned-out solenoid in the oil supply valve
Related regulation: NVIC 01-69 Encl.1 — Automated Main and Auxiliary Machinery — Enclosure (1)
Question 6 · UFIV – Assistant Engineer
The turbocharged, four-stroke, main propulsion diesel engines on your fishery research vessel are protected with dry-type air intake filters. The engines are fitted with dial-type restriction indicators measuring the pressure in the air duct between the air intake filter and the turbocharger blower inlet. Under what conditions should the air intake filters be evaluated using the restriction indicators?
- A.The engine should be running at rated RPM with full load (propulsion clutch engaged). (correct answer)
- B.The engine should be running at idle RPM with minimal load (propulsion clutch engaged).
- C.The engine should be running at rated RPM with no load (propulsion clutch disengaged).
- D.The engine should be running at idle RPM with no load (propulsion clutch disengaged).
Answer: A. The engine should be running at rated RPM with full load (propulsion clutch engaged).
Related regulation: 46 CFR 182.465 ↗ — Ventilation of spaces containing diesel machinery
Question 7 · OSV – Assistant Engineer
The diesel engines on your general-purpose supply vessel are all protected with dry-type air filters. The air filters should be inspected and replaced in accordance with manufacturer instructions. What is the generally accepted criteria that would dictate when filter replacement becomes necessary?
- A.The air filter element should be replaced when the pressure drop across the element increases above the specified maximum. (correct answer)
- B.The air filter element should be replaced when the pressure rise across the element decreases below the specified minimum.
- C.The air filter element should be replaced when the pressure drop across the element decreases below the specified minimum.
- D.The air filter element should be replaced when the pressure rise across the element increases above the specified maximum.
Answer: A. The air filter element should be replaced when the pressure drop across the element increases above the specified maximum.
Related regulation: 46 CFR 143.255 — Fuel system requirements
Question 8 · DDE – 1000/4000 HP
Concerning the diesel fuels used for the auxiliary and main propulsion diesel engines used on board the towing vessel to which you are assigned, what fuel property is directly a measure of the ignition quality of the fuel?
- A.Heating value
- B.Cetane rating (correct answer)
- C.Viscosity
- D.Density
Answer: B. Cetane rating
Related regulation: MARPOL Amendments MEPC.328(76) Ch.8 — MARPOL Amendments Chapter 8 — The bunker delivery note shall be accompanied by a representative sample of the fuel
Question 9 · MODU – Chief Engineer
While bunkering heavy fuel, what quick/easy test can one perform onboard to determine the compatibility of 'old' with 'new' fuel?
- A.Take equal samples of both fuels, elevate their temperature, and mix them vigorously. If no frothing occurs, they are compatible.
- B.Perform a running viscosity test of both fuels, at the same temperature, if the viscosities are equal, they should be compatible.
- C.Mix two equal samples of the two fuels at elevated temperatures and determine if they become a homogeneous mixture.
- D.Use blotter paper with a single concentric drop of 'old' and 'new' fuel, if they do not form separate circles, the fuels may be deemed compatible. (correct answer)
Answer: D. Use blotter paper with a single concentric drop of 'old' and 'new' fuel, if they do not form separate circles, the fuels may be deemed compatible.
Related regulation: MARPOL Amendments MEPC.328(76) Ch.8 — MARPOL Amendments Chapter 8 — The bunker delivery note shall be accompanied by a representative sample of the fuel
Question 10 · Third Assistant Engineer
Which internal combustion engine starting system uses a vane type fluid motor?
- A.Jet flow
- B.Compressed air (correct answer)
- C.Electric
- D.Centrifugal
Answer: B. Compressed air
Related regulation: 46 CFR 112.50-7 ↗ — Compressed air starting

Exams these questions come from

Choose one when you start the quiz. A question can appear in more than one exam, so these add up to more than 492.

Third Assistant Engineer99 questions
MODU – Chief Engineer54 questions
Assistant Engineer – Limited52 questions
Chief Engineer – Limited47 questions
First Assistant Engineer44 questions
OSV – Chief Engineer43 questions
MODU – Assistant Engineer38 questions
DDE – Unlimited HP34 questions
UFIV – Chief Engineer34 questions
OSV – Assistant Engineer33 questions
UFIV – Assistant Engineer23 questions
DDE – 1000/4000 HP21 questions

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Offshore Installation Manager (OIM) · 288

The questions and answer keys are from the U.S. Coast Guard National Maritime Center’s published sample exams. RegKnot is not affiliated with the U.S. Coast Guard or the National Maritime Center. A practice score does not predict your exam result; check the NMC for current exam requirements.

USCG Motor Plants Practice Test

Take a 10-question quiz

10 sample Motor Plants questions with answers

Which of the following actions takes place in the control circuit of an automatically fired auxiliary boiler when the desired steam pressure is obtained?

Assuming the use of ultra-low sulfur content diesel fuel, what combination of conditions associated with uninspected fishing industry vessel engine room operations would require the most frequent draining of exhaust systems of condensation?

Due to the questionable mineral content of fresh water taken on from shore as a source of make-up water for diesel engine closed, recirculating cooling water systems, besides chemical treatment and coolant testing, what is the best line of defense in minimizing cooling system problems?

The primary function of a flame safeguard system, as used on an automatically fired auxiliary boiler, is to prevent what condition?

Burner ignition failure in an automatically fired auxiliary boiler would be caused by __________.

The diesel engines on your general-purpose supply vessel are all protected with dry-type air filters. The air filters should be inspected and replaced in accordance with manufacturer instructions. What is the generally accepted criteria that would dictate when filter replacement becomes necessary?

Concerning the diesel fuels used for the auxiliary and main propulsion diesel engines used on board the towing vessel to which you are assigned, what fuel property is directly a measure of the ignition quality of the fuel?

While bunkering heavy fuel, what quick/easy test can one perform onboard to determine the compatibility of 'old' with 'new' fuel?

Which internal combustion engine starting system uses a vane type fluid motor?