Or Motor Unlimited Examination

Coast Guard Assistant Engineer (Steam Or Motor) Unlimited Examination Practice Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• What is the primary purpose of a lube oil cooler in a propulsion engine?
• Reduce scavenge air temperature
• Increase oil viscosity
• Maintain proper operating oil temperature
• Prevent fuel dilution

Rationale: Proper oil temperature ensures lubrication quality and protects

engine parts.

• Which component controls steam pressure in a fire-tube boiler?
• Steam drum
• Economizer 1 / 4

• Safety valve
• Air preheater

Rationale: The safety valve automatically relieves excess pressure to

prevent boiler explosions.

3. In a diesel engine, the purpose of the governor is to:

• Control fuel atomization
• Regulate jacket water flow
• Maintain engine speed under varying loads
• Adjust intake air pressure

Rationale: Governors modulate fuel delivery to keep RPM constant.

• What does an auxiliary condenser typically do?
• Heats feedwater
• Cools main steam
• Condenses auxiliary exhaust steam
• Maintains vacuum

Rationale: Auxiliary condensers handle exhaust from auxiliary turbines and

equipment.

• Sludge in lube oil is normally removed by which equipment?
• Evaporator
• Purifier/clarifier
• Bilge pump
• Deaerator 2 / 4

Rationale: Purifiers separate contaminants like sludge, water, and solids

from lube oil.

6. Low water in a boiler can result in:

• Soot buildup
• Overheating and potential boiler explosion
• High superheat
• Excessive priming

Rationale: Low water exposes boiler tubes, causing overheating and

catastrophic failure.

7. The primary function of an air start motor is to:

• Provide combustion air
• Regulate engine timing
• Rotate the engine to starting speed
• Cool pistons

Rationale: Compressed air rotates the engine for starting in large diesel

systems.

8. The main purpose of a fuel injector nozzle is to:

• Meter intake air
• Preheat fuel
• Atomize fuel for combustion
• Increase fuel viscosity

Rationale: Fine atomization ensures efficient and complete combustion. 3 / 4

9. The economizer in a steam plant recovers heat from:

• Feedwater
• Main steam
• Boiler flue gases
• Makeup water

Rationale: Economizers reclaim heat from exhaust gases to warm

feedwater.

10. A purifier bowl speed that is too low will result in:

• Oil overheating
• Poor separation efficiency
• Loss of water seal
• Excessive sludge discharge

Rationale: High centrifugal force is needed for proper oil-water-solid

separation.

11. Cylinder glazing occurs due to:

• High sulfur fuel
• Low engine loading for extended periods
• Excess lube oil consumption
• High jacket water temperatures

Rationale: Light loads prevent proper ring seating and lead to smooth

glazed cylinder surfaces.

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