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USCG OIM practice questions

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Question 1Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

In a four-stroke diesel engine, during which stroke is the intake valve normally open?

  1. The compression stroke
  2. The intake stroke Correct answer.
  3. The exhaust stroke
  4. The power stroke

Explanation

The intake valve opens as the piston moves down on the intake stroke to admit fresh air. It is held closed through compression, power, and exhaust to seal the cylinder.

Question 2Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

What is the primary purpose of lube oil in a marine diesel engine?

  1. To raise the cetane number of the fuel
  2. To reduce friction and carry away heat Correct answer.
  3. To increase compression ratio
  4. To cool the combustion air

Explanation

Lube oil forms a film between moving surfaces to reduce friction and wear while also removing heat from bearings and pistons. It does not affect compression ratio, fuel cetane, or intake air temperature.

Question 3Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

A vessel's main engine is running and the low lube oil pressure alarm sounds. What is the most appropriate immediate action?

  1. Ignore the alarm until the next watch change
  2. Add fuel to the day tank
  3. Increase engine speed to raise pump output
  4. Reduce load and investigate the lube oil system Correct answer.

Explanation

Low lube oil pressure threatens bearing damage, so the engine load should be reduced and the system investigated promptly. Raising speed increases demand on the oil system and worsens the condition.

Question 4Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

What does the term 'dead slow' typically describe in engine order telegraph usage?

  1. The minimum ahead speed setting Correct answer.
  2. Full astern power
  3. A standby condition
  4. A stopped propeller

Explanation

Dead slow is the lowest ahead speed command on the telegraph, used for maneuvering in confined waters. It is not a stop, full astern, or standby order.

Question 5Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

Which device removes water and solid contaminants from fuel oil before it reaches the engine?

  1. The air receiver
  2. The turbocharger
  3. The expansion tank
  4. The fuel oil purifier Correct answer.

Explanation

A fuel oil purifier uses centrifugal force to separate water and solids from the fuel. The turbocharger, air receiver, and expansion tank serve unrelated functions.

Question 6Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

What is the function of a sea water cooling system on a diesel engine?

  1. To reject heat from the fresh water cooling circuit Correct answer.
  2. To supply combustion air
  3. To pressurize the fuel system
  4. To lubricate the cylinder liners

Explanation

Sea water passes through heat exchangers to remove heat picked up by the closed fresh water circuit. It does not lubricate liners, feed combustion air, or pressurize fuel.

Question 7Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

In a watchkeeping routine, how often should engine room log readings normally be recorded?

  1. At regular intervals set by standing orders Correct answer.
  2. Only at the end of each voyage
  3. Only when an alarm occurs
  4. Once per month

Explanation

Engine room logs are kept at regular intervals specified in standing orders to track machinery trends. Recording only at voyage end, on alarm, or monthly would not provide adequate monitoring.

Question 8Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

What is the purpose of the starting air system on a large marine diesel engine?

  1. To cool the exhaust gases
  2. To rotate the engine until it fires Correct answer.
  3. To filter the lube oil
  4. To supply fuel to the injectors

Explanation

Compressed starting air is admitted to the cylinders to turn the engine over until combustion begins. It does not cool exhaust, filter oil, or deliver fuel.

Question 9Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

A diesel engine's exhaust gas temperature rises sharply on one cylinder while the others remain normal. Which condition is most likely?

  1. A clogged sea water strainer for the whole engine
  2. A low level in the expansion tank
  3. A faulty fuel injector on that cylinder Correct answer.
  4. A worn starting air valve

Explanation

A single-cylinder exhaust temperature deviation most often points to a fuel injection fault such as a dribbling or partially blocked injector. System-wide cooling or air faults would affect all cylinders.

Question 10Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

What does a rising trend in lube oil consumption most likely indicate?

  1. A blocked fuel filter
  2. Low starting air pressure
  3. Worn piston rings or liners Correct answer.
  4. A faulty tachometer

Explanation

Increasing lube oil consumption commonly signals worn piston rings or cylinder liners allowing oil past into the combustion space. Fuel filters, starting air, and tachometers do not consume lube oil.

Question 11Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

Why is it important to warm the engine before applying full load after a cold start?

  1. To reduce the fuel's cetane number
  2. To allow oil to reach all bearing surfaces and clearances to stabilize Correct answer.
  3. To increase the starting air pressure
  4. To lower the sea water temperature

Explanation

Gradual warming lets lubricating oil circulate fully and allows thermal expansion of components to stabilize before high loads are applied. It does not alter fuel cetane, starting air pressure, or sea water temperature.

Question 12Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

What is the purpose of the crankcase breather on a diesel engine?

  1. To supply oil to the bearings
  2. To drain fuel from the injectors
  3. To vent blow-by gases and prevent pressure build-up Correct answer.
  4. To admit starting air

Explanation

The breather relieves pressure from blow-by gases entering the crankcase and prevents seals from being stressed. It does not deliver oil, admit air, or drain fuel.

Question 13Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

During a maneuvering watch, the engine order telegraph is tested before arrival primarily to:

  1. Warm the fuel oil
  2. Confirm reliable communication between bridge and engine room Correct answer.
  3. Charge the starting air bottles
  4. Test the steering gear

Explanation

Testing the telegraph before maneuvering confirms the bridge and engine room can exchange orders reliably in confined waters. It does not warm fuel, charge air, or test steering gear.

Question 14Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

A high exhaust temperature on all cylinders with normal cooling water temperatures most likely indicates:

  1. Engine overload or excessive fuel delivery Correct answer.
  2. A faulty starting air valve
  3. Low lube oil pressure
  4. A single failed injector

Explanation

Uniformly high exhaust temperatures across all cylinders with normal cooling typically reflect overload or over-fueling. A single injector fault would affect only one cylinder, and lube oil or starting air faults do not cause this pattern.

Question 15Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

What is the function of a turbocharger on a marine diesel engine?

  1. To filter the fuel
  2. To reduce engine noise
  3. To cool the lube oil
  4. To increase the mass of air delivered to the cylinders Correct answer.

Explanation

The turbocharger uses exhaust gas energy to drive a compressor that increases charge air density, allowing more fuel to be burned. It does not cool oil, filter fuel, or primarily reduce noise.

Question 16Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

An engine room watchkeeper notices the bilge level rising slowly in the engine room. What is the correct first action?

  1. Identify and stop the source of the leak Correct answer.
  2. Open the sea water injection valve
  3. Increase the fuel transfer rate
  4. Reduce the lube oil pressure

Explanation

The priority is to find and stop the source of the ingress while ensuring bilge pumping keeps pace. Opening sea water injection, increasing fuel transfer, or reducing lube oil pressure do not address the leak.

Question 17Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

Why must fuel oil be heated before atomization in some diesel engines?

  1. To increase its sulfur content
  2. To raise its flash point
  3. To reduce viscosity for proper injection and atomization Correct answer.
  4. To increase its cetane number

Explanation

Heavy fuel oils are viscous and must be heated to lower viscosity so the injectors can atomize them properly. Heating does not change cetane number, flash point, or sulfur content.

Question 18Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

What is the purpose of the cylinder liner cooling water in a diesel engine?

  1. To lubricate the piston rings
  2. To supply combustion air
  3. To remove heat and maintain proper clearances Correct answer.
  4. To clean the fuel injectors

Explanation

Cooling water removes heat from the liner to maintain metal temperatures and clearances within design limits. It does not lubricate rings, supply air, or clean injectors.

Question 19Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

During a routine watch, the lube oil filter differential pressure rises steadily. What does this indicate and what action is appropriate?

  1. High oil temperature; bypass the cooler
  2. A clogging filter; switch to the standby filter and clean it Correct answer.
  3. Low oil level; add oil to the sump
  4. A failing lube oil pump; increase engine speed

Explanation

Rising differential pressure across a filter signals increasing restriction from accumulated contaminants, so the standby filter should be placed in service and the clogged one cleaned. Increasing speed, adding oil, or bypassing the cooler do not address filter restriction.

Question 20Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

What is the primary reason for conducting regular crankcase oil analysis?

  1. To measure the engine's fuel consumption
  2. To detect wear metals and contamination trends early Correct answer.
  3. To set the engine's timing
  4. To check starting air pressure

Explanation

Oil analysis detects wear metals, water, and other contaminants so developing problems can be addressed before failure. It does not measure fuel consumption, set timing, or check air pressure.

Question 21Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

A diesel engine fails to start on air. Which condition would most directly prevent rotation?

  1. Insufficient starting air pressure Correct answer.
  2. Dirty fuel oil
  3. Low sea water temperature
  4. High lube oil temperature

Explanation

Starting air must have sufficient pressure to turn the engine; low pressure prevents rotation. Oil temperature, fuel cleanliness, and sea water temperature do not directly prevent cranking.

Question 22Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

How does a governor control a marine diesel engine?

  1. By varying the cooling water flow
  2. By adjusting fuel delivery to maintain the set speed Correct answer.
  3. By changing the valve timing
  4. By regulating starting air pressure

Explanation

The governor senses engine speed and adjusts fuel rack position to hold the desired speed under varying load. It does not control cooling flow, valve timing, or starting air.

Question 23Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

What is the significance of a rising piston cooling oil outlet temperature on one unit?

  1. A sign of low starting air pressure
  2. An indication of high fuel cetane
  3. A normal condition at all loads
  4. Possible blockage or reduced flow in that piston's cooling circuit Correct answer.

Explanation

A localized rise in piston cooling oil outlet temperature points to restricted flow or a blockage in that circuit, risking piston overheating. It is not a normal condition, and starting air or fuel cetane do not cause it.

Question 24Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

A watchkeeper must decide whether to run the standby generator during a heavy maneuvering evolution. The most important consideration is:

  1. Reducing fuel consumption to a minimum
  2. Increasing the starting air pressure
  3. Ensuring adequate reserve power and redundancy for load changes Correct answer.
  4. Lowering the sea water temperature

Explanation

Maneuvering involves rapid load changes and thruster or steering demands, so reserve generating capacity and redundancy are critical to avoid blackout. Fuel economy, sea water temperature, and starting air pressure are secondary to maintaining power availability.

Question 25Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

Why is a controlled load reduction required when a turbocharger develops a fault at sea?

  1. To raise the starting air pressure
  2. To increase the fuel's cetane number
  3. To lower the lube oil viscosity
  4. To prevent over-fueling and excessive thermal load without adequate charge air Correct answer.

Explanation

With reduced charge air from a faulty turbocharger, the engine cannot burn the same fuel quantity cleanly, so load must be reduced to avoid over-fueling and excessive thermal stress. It does not change fuel cetane, starting air pressure, or oil viscosity.

Question 26Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

In a four-stroke diesel engine, what is the primary function of the camshaft?

  1. It operates the intake and exhaust valves at the correct time relative to piston position Correct answer.
  2. It drives the seawater cooling pump directly
  3. It regulates the engine speed through centrifugal force
  4. It meters the quantity of fuel delivered to each cylinder

Explanation

The camshaft converts rotary motion of the crankshaft into timed linear motion that opens and closes the intake and exhaust valves in step with the piston cycle. Fuel quantity is set by the fuel injection pump, not the camshaft, and speed regulation is the governor's job.

Question 27Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

What is the purpose of a purifier in a marine fuel oil or lube oil system?

  1. It removes water and solid contaminants by centrifugal separation Correct answer.
  2. It filters out particles larger than ten microns
  3. It raises the oil pressure before the engine inlet
  4. It cools the oil before it returns to the sump

Explanation

A purifier uses high-speed centrifugal force to separate water and heavier solids from oil based on density difference. Filtration and cooling are separate functions handled by filters and coolers.

Question 28Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

What does the term 'dead ship condition' mean in the context of a vessel's machinery?

  1. The vessel is alongside with shore power connected
  2. The main propulsion and all auxiliary power sources are not functioning Correct answer.
  3. The engine room is unmanned and alarms are disabled
  4. The main engine is running but the steering gear has failed

Explanation

Dead ship condition describes a state in which the main propulsion plant and all auxiliary power, including the emergency generator, are out of action. It is a critical safety scenario addressed by emergency procedures and drills.

Question 29Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

Why is a boiler water level gauge glass blown through periodically?

  1. To confirm the water level indication is clear and not falsely high or low Correct answer.
  2. To reduce the boiler drum pressure
  3. To add chemicals to the boiler water
  4. To warm the gauge glass before reading

Explanation

Blowing through the gauge glass clears sediment and confirms that the indicated level is genuine, preventing a false reading that could lead to a dangerous low-water condition. It does not change drum pressure or treat the water.

Question 30Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

What is the main function of a reduction gearbox between a medium-speed engine and the propeller shaft?

  1. It supplies lube oil to the main engine bearings
  2. It separates the engine from the shaft during starting
  3. It reduces shaft speed while increasing torque to the propeller Correct answer.
  4. It increases shaft speed to suit a high-speed propeller

Explanation

A reduction gearbox matches the high operating speed of a medium-speed engine to the lower speed required by an efficient propeller, trading speed for torque. It is not a clutch and does not supply engine lube oil.

Question 31Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

What is the primary function of the air receiver in a starting air system?

  1. It cools the compressed air before it reaches the engine
  2. It stores compressed air at working pressure to supply starting and control air Correct answer.
  3. It removes oil and moisture from the compressed air
  4. It regulates the engine speed during starting

Explanation

The air receiver is a pressure vessel that stores sufficient compressed air to provide the multiple starting attempts required by class rules. Cooling and moisture removal occur at the compressor and separators, not the receiver.

Question 32Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

What is the purpose of the jacket water expansion tank on a diesel engine cooling system?

  1. It traps air and discharges it to the bilge
  2. It acts as a heat exchanger to cool the jacket water
  3. It allows coolant to expand and contract while maintaining a static head on the system Correct answer.
  4. It stores reserve coolant for emergency injection into the cylinders

Explanation

The expansion tank accommodates the volume change of the coolant as it heats and cools and maintains a positive static head that suppresses cavitation and aids air separation. It is not a heat exchanger and does not inject coolant into cylinders.

Question 33Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

What does the term 'bumping' or 'barring' the engine refer to before starting?

  1. Raising the cylinder pressure to test compression
  2. Testing the overspeed trip mechanism
  3. Turning the engine slowly to confirm it rotates freely and to distribute lube oil Correct answer.
  4. Heating the fuel to improve atomization

Explanation

Barring the engine rotates the crankshaft slowly, confirming there is no hydraulic lock or mechanical obstruction and spreading lube oil over the bearing surfaces before start. It does not test compression or the overspeed trip.

Question 34Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

A watchkeeper observes the main engine lube oil pressure slowly falling while the engine load and temperature remain steady. Which action is most appropriate?

  1. Start the standby lube oil pump and investigate the cause before the pressure reaches the low alarm Correct answer.
  2. Ignore the trend until the low pressure alarm sounds
  3. Increase engine load to raise oil pressure
  4. Reduce the cooling water flow to the oil cooler

Explanation

A steady pressure loss with unchanged load points to a developing fault such as a filter blockage, pump wear, or a leak, and the standby pump should be started to protect the bearings while the cause is found. Increasing load or waiting for the alarm risks bearing damage.

Question 35Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

During a watch, the scavenge air pressure of a turbocharged engine drops while exhaust temperature rises across all cylinders. What is the most likely cause?

  1. A misaligned propeller shaft
  2. A single leaking exhaust valve
  3. Fouling of the turbocharger or air cooler reducing charge air supply Correct answer.
  4. Low fuel oil viscosity

Explanation

Reduced scavenge air pressure with rising exhaust temperature across all cylinders indicates the turbocharger or air cooler is not delivering sufficient charge air, so more fuel burns late and hotter. A single valve fault would affect one cylinder, not all.

Question 36Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

Why must the main engine be placed on the turning gear before working on a cylinder unit?

  1. To allow the governor to be tested
  2. To prevent accidental rotation of the crankshaft while personnel are inside the crankcase Correct answer.
  3. To maintain starting air pressure
  4. To keep the lube oil warm during the work

Explanation

Engaging the turning gear mechanically locks the crankshaft so that a starting air admission or turning force cannot rotate the engine while personnel are working inside. It is a personnel-safety interlock, not a thermal or control function.

Question 37Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

What is the primary purpose of the crankcase oil mist detector?

  1. To measure the viscosity of the lube oil in service
  2. To monitor the oil level in the sump tank
  3. To detect water contamination in the sump
  4. To give early warning of a hot spot that could lead to a crankcase explosion Correct answer.

Explanation

An oil mist detector senses the increase in oil mist density that precedes a crankcase explosion, allowing the engine to be slowed and stopped before ignition occurs. Viscosity, water content, and level are monitored by other means.

Question 38Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

A generator prime mover begins to hunt, with speed oscillating around the set point. Which component is most directly implicated?

  1. The air cooler
  2. The governor and its feedback linkage Correct answer.
  3. The fuel transfer pump
  4. The alternator exciter

Explanation

Hunting is a control instability in which the governor overcorrects and the speed oscillates, so the governor and its feedback linkage are the primary suspect. The exciter affects voltage, and the fuel transfer pump and air cooler do not control speed.

Question 39Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

Why is a main engine cooling water system treated with corrosion inhibitors and tested regularly?

  1. To raise the boiling point of the coolant above the operating temperature
  2. To lubricate the cooling water pump bearings
  3. To protect ferrous and non-ferrous metals from corrosion and scale that reduce heat transfer Correct answer.
  4. To increase the specific heat of the coolant

Explanation

Chemical treatment controls corrosion, scale, and biological growth that would otherwise impair heat transfer and damage the engine. The coolant's boiling point and specific heat are essentially fixed by its composition, and pump bearings are lubricated separately.

Question 40Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

During an unmanned machinery space watch, the engineer is called to the engine room by a dead ship alarm. What should be verified first on arrival?

  1. Whether the fuel oil transfer pump is running
  2. Whether the steering gear is on hand hydraulic control
  3. Whether the main switchboard has power and the emergency generator has started Correct answer.
  4. Whether the boiler is at working pressure

Explanation

The priority in a dead ship alarm is to confirm whether the main switchboard is energised and whether the emergency generator has automatically started, since all other systems depend on electrical power. Fuel transfer, boiler pressure, and steering follow once power is restored.

Question 41Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

What is the effect of a clogged lube oil cooler on engine operation?

  1. Oil temperature rises and viscosity falls, reducing bearing film strength Correct answer.
  2. Oil pressure rises sharply because flow is restricted
  3. Oil consumption decreases as less oil vaporises
  4. Cooling water temperature falls below normal

Explanation

A clogged cooler cannot reject heat, so oil temperature rises and viscosity drops, thinning the oil film and risking bearing wear. Restriction in the cooler tends to reduce flow rather than raise pressure, and cooling water temperature would rise.

Question 42Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

Why is a fuel oil viscosity controller used on engines burning heavy fuel oil?

  1. To hold viscosity at the value that gives correct atomization at the injectors Correct answer.
  2. To prevent the fuel from freezing in the storage tanks
  3. To measure the calorific value of the fuel
  4. To control the sulphur content of the fuel

Explanation

Heavy fuel must be heated to a viscosity that allows proper atomization; too high and the spray is poor, too low and lubrication and combustion suffer. The controller regulates heater output to maintain that viscosity set point.

Question 43Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

An engineer finds water in the lube oil sump of a diesel engine. Which consequence is most serious if operation continues?

  1. Reduced crankcase pressure
  2. Higher oil viscosity improving protection
  3. Loss of lubricating film and corrosion of bearing surfaces Correct answer.
  4. Increased oil pressure at the bearings

Explanation

Water emulsifies with oil, reducing its load-carrying film and promoting corrosion and sludge on bearing surfaces, which can lead to failure. Water does not improve viscosity or raise pressure in a beneficial way.

Question 44Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

What is the purpose of the interlock that prevents starting the main engine with the turning gear engaged?

  1. To ensure the lube oil pump runs before starting
  2. To confirm the fuel oil booster pump is running
  3. To prevent cranking against a locked shaft, which could damage the turning gear or starting system Correct answer.
  4. To verify the governor is in the run position

Explanation

If starting air were admitted while the turning gear is engaged, the engine could not rotate and the resulting torque could wreck the turning gear or starting system. The interlock blocks starting until the gear is disengaged.

Question 45Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

A watchkeeper notices the boiler burner flame is unstable and the flame scanner keeps tripping the burner. What is the most appropriate response?

  1. Increase the fuel supply to stabilise the flame
  2. Bypass the flame scanner to keep the boiler online
  3. Trip the boiler, investigate fuel pressure, atomization, and scanner condition, then relight per procedure Correct answer.
  4. Reduce the combustion air supply to strengthen the flame

Explanation

An unstable flame with repeated scanner trips is a furnace explosion hazard, so the boiler should be tripped and the fuel and air systems and scanner checked before a controlled relight. Increasing fuel or bypassing the scanner risks an explosion.

Question 46Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

During maneuvering, the main engine repeatedly fails to reverse on air. Which condition best explains this?

  1. Insufficient starting air pressure or a faulty reversing linkage preventing correct air timing Correct answer.
  2. Low jacket water temperature
  3. Excessive lube oil temperature
  4. A dirty fuel oil filter

Explanation

Reversal requires sufficient air pressure and correct positioning of the reversing gear so that starting air is admitted to the proper cylinders for the new direction. Low air pressure or a mispositioned reversing linkage directly prevents reversal, while the other conditions do not.

Question 47Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

Why must a turbocharger that has suffered a bearing failure be isolated and the engine load reduced before continuing?

  1. The fuel oil system will overheat without turbocharging
  2. The governor will lose speed control
  3. The engine will automatically shut down on overspeed
  4. The rotor may seize or overspeed, and reduced load lowers charge air demand and exhaust energy Correct answer.

Explanation

A damaged turbocharger rotor can seize or overspeed and shed parts, so it is isolated and the engine is derated to keep exhaust energy and charge air demand within safe limits. The engine does not automatically shut down, and the governor and fuel system remain functional.

Question 48Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

What is the significance of a steadily increasing differential pressure across the fuel oil fine filter during operation?

  1. The filter element is loading up and should be changed or the standby filter cut in Correct answer.
  2. The fuel pump is delivering excess flow
  3. The fuel viscosity has fallen below specification
  4. The fuel heater has failed

Explanation

Differential pressure rises as contaminants accumulate on the element, and once it approaches the change-out limit the standby filter should be cut in to protect the injection equipment. Falling viscosity or a failed heater would not raise filter differential pressure.

Question 49Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

An engine room watchkeeper must decide whether to run a second generator in parallel during a heavy load change. Which factor is most important in that decision?

  1. The load margin and the ability of the online generator to absorb the expected transient without tripping Correct answer.
  2. The ambient temperature of the switchboard room
  3. The fuel oil consumption of the standby unit
  4. The colour of the exhaust from the running generator

Explanation

The decision turns on whether the online generator has enough reserve to ride through the expected transient load without exceeding its capacity or tripping on overload. Exhaust appearance, standby fuel consumption, and switchboard room temperature are secondary considerations.

Question 50Engineering knowledge and watchkeeping (engine room systems, machinery operation, and maintenance)

What is the correct procedure for changing over the main engine lube oil filters while the engine is running?

  1. Cut in the standby filter, confirm pressure is stable, then clean the dirty filter and return it to standby Correct answer.
  2. Drain the dirty filter housing to the bilge before cutting in the standby unit
  3. Stop the engine, change the element, and restart
  4. Close the filter inlet and outlet valves, then open the housing immediately

Explanation

The standby filter is first brought online so that flow is maintained, pressure is confirmed stable, and only then is the dirty filter isolated, cleaned, and returned to standby. Stopping the engine or opening the housing without first cutting in the standby unit risks loss of lubrication.