Examination Questions And Correct

Coast Guard Designated Duty Engineer (DDE) – 1,000 Horsepower Practice Examination Questions And ( Answers) Plus Rationales 2026 Q&A Instant Download Pdf

• The primary purpose of a cylinder lubricating oil in a diesel engine is

to:

• Cool the piston rings
• Reduce friction between moving parts
• Seal the combustion chamber
• Increase fuel efficiency

Rationale: Cylinder lubricating oil primarily reduces friction and wear

between moving engine components, ensuring smooth operation.

2. A centrifugal pump is classified as:

• Positive displacement
• Dynamic pump 1 / 4

• Reciprocating pump
• Rotary pump

Rationale: Centrifugal pumps impart velocity to the fluid, converting

it to pressure energy, which classifies them as dynamic pumps.

3. The boiler water level should never fall below the:

• Gauge glass top
• Lowest permissible water level line
• Safety valve
• Steam drum top

Rationale: Maintaining water above the minimum level prevents

boiler tube overheating and potential failure.

• A ship’s main engine has a maximum continuous rating (MCR) of 1,200

HP. For continuous operation, it should be run at:

• 50% of MCR
• 75% of MCR
• of MCR
• 110% of MCR

Rationale: Maximum continuous rating defines the highest output

the engine can sustain continuously under normal conditions.

5. The purpose of a bilge alarm is to:

• Prevent flooding
• Start the bilge pump automatically
• Warn the crew of excessive water accumulation 2 / 4

• Activate fire suppression systems

Rationale: Bilge alarms alert crew to excessive water in the bilge,

allowing timely corrective action.

6. In a diesel engine, pre-combustion chambers are used to:

• Increase fuel economy
• Improve combustion efficiency
• Reduce engine weight
• Reduce exhaust temperature

Rationale: Pre-combustion chambers promote better fuel-air mixing,

resulting in more complete combustion.

7. The purpose of a turbine governor is to:

• Stop the turbine in emergencies
• Maintain desired speed under varying load
• Reduce fuel consumption
• Increase turbine efficiency

Rationale: A governor automatically adjusts fuel or steam supply to

maintain constant turbine speed despite load changes.

8. When starting a diesel engine, it is important to:

• Open the main fuel valve fully
• Ensure proper lubrication and pre-lubricate if necessary
• Load the engine immediately
• Close all air intake valves 3 / 4

Rationale: Proper lubrication prevents dry-start wear and damage to

engine components.

• The main advantage of a two-stroke diesel engine over a four-stroke

is:

• Lower maintenance
• Higher power-to-weight ratio
• Better fuel efficiency
• Lower exhaust temperature

Rationale: Two-stroke engines produce power every revolution,

giving a higher power-to-weight ratio.

10. The function of the crankcase ventilation system is to:

• Cool the engine
• Supply air to the cylinders
• Remove blow-by gases and prevent pressure buildup
• Increase engine efficiency

Rationale: Ventilation removes gases that escape past piston rings to

prevent crankcase pressure and oil contamination.

11. The flash point of diesel fuel is typically:

A. 38°C

B. 50°C

C. 52–96°C

• 100°C
• / 4