Examination Practice Questions And

Coast Guard Able Seafarer–Engine Examination Practice Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• What is the primary function of a ship’s main engine?
• Generate electricity
• Provide propulsion
• Control ship navigation
• Operate auxiliary machinery

Rationale: The main engine’s primary purpose is to provide

propulsion to move the vessel through the water.

• What type of fuel is commonly used in large marine diesel engines?
• Gasoline
• Heavy fuel oil (HFO) 1 / 4

• Kerosene
• Ethanol

Rationale: Large marine diesel engines typically run on heavy fuel oil

due to its high energy content and cost-effectiveness.

• Which component of a diesel engine compresses air before fuel

injection?

• Cylinder liner
• Piston and cylinder
• Turbocharger
• Fuel injector

Rationale: The piston compresses air in the cylinder, raising its

temperature to ignite fuel.

• What is the purpose of a ship’s auxiliary engine?
• Propulsion during maneuvering
• Generate electricity for shipboard systems
• Reduce main engine load
• Operate lifeboat engines

Rationale: Auxiliary engines are primarily used to produce electrical

power for onboard systems.

• Which device is used to remove impurities from fuel before it enters

the engine?

• Heat exchanger
• Fuel purifier 2 / 4

• Bilge pump
• Centrifugal governor

Rationale: A fuel purifier (or centrifuge) removes water and solid

impurities to prevent engine damage.

• What is the normal operating temperature range for a ship’s main

engine cooling system?

A. 20–40°C

B. 50–70°C

C. 80–95°C

D. 100–120°C

Rationale: Most marine diesel engines operate with cooling water

temperatures around 80–95°C for optimal efficiency and engine life.

• Which type of lubrication system is commonly used in marine

engines?

• Splash lubrication
• Forced-feed (pressure) lubrication
• Gravity lubrication
• Wick lubrication

Rationale: Marine diesel engines use a pressurized lubrication system

to ensure all moving parts receive adequate oil.

• What is the primary purpose of a turbocharger in a marine diesel

engine?

• Reduce exhaust emissions 3 / 4

• Increase engine power by forcing more air into cylinders
• Lower engine temperature
• Purify fuel

Rationale: A turbocharger increases the engine’s efficiency and

power by compressing air into the cylinders.

• How is engine speed typically controlled on a marine diesel engine?
• By adjusting turbocharger blades
• By using a fuel cutoff valve
• By a governor regulating fuel injection
• By changing cooling water flow

Rationale: The governor adjusts fuel delivery to maintain a constant

engine speed.

• What type of pump is commonly used for circulating cooling

water in marine engines?

• Gear pump
• Centrifugal pump
• Centrifugal pump
• Reciprocating pump

Rationale: Centrifugal pumps are commonly used to circulate

seawater or freshwater in engine cooling systems.

• What does the term “scavenge air” refer to in a diesel engine?
• Exhaust gas recirculation
• Air in the fuel line
• / 4