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MARINA OIC-EW Theoretical Exam study materials
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MARINA OIC-EW Theoretical Exam practice questions

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Question 1Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

During a routine watch, the main engine cylinder liner temperature on one unit begins rising while the other units remain steady, and the exhaust gas temperature for that unit is also elevated. Which immediate action is most appropriate before making any adjustment?

  1. Reduce the load on that cylinder by isolating its fuel pump and continue the voyage
  2. Verify the reading with a second means of measurement and compare against the other units to confirm the deviation is real Correct answer.
  3. Increase the cylinder lubricating oil feed rate to that unit and monitor for one hour
  4. Open the indicator cock on that unit to relieve suspected high combustion pressure

Explanation

A single-unit temperature deviation should first be confirmed as genuine before any corrective action is taken; instrumentation faults are common and acting on a false reading can create a real fault. Cross-checking with a second measurement and comparing against sister units establishes whether the deviation is real and how severe it is. Only after confirmation should fuel, lubrication, or load be adjusted.

Question 2Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

In a large two-stroke crosshead main engine, which component carries the gas load from the piston to the connecting rod while keeping the crankcase free of combustion products?

  1. The piston rod and stuffing box arrangement Correct answer.
  2. The scavenge air receiver
  3. The telescopic pipe assembly
  4. The crosshead bearing shell

Explanation

In a crosshead engine the piston rod transmits the gas force from the piston down to the crosshead, and the stuffing box seals the rod as it passes through the diaphragm so that combustion products and scavenge air stay out of the crankcase. The telescopic pipes supply cylinder lubricating oil and do not carry gas load. The crosshead bearing carries the rod load to the guide shoes but is inside the crankcase.

Question 3Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

A main engine turbocharger begins surging at high load. Which condition is the most likely direct cause?

  1. Fuel injection timing advanced by one degree across all units
  2. A fouled compressor or turbine side causing the operating point to move toward the surge line Correct answer.
  3. Cylinder lubricating oil feed set slightly above the recommended rate
  4. Excessive cooling water flow through the charge air cooler

Explanation

Surge occurs when the compressor cannot sustain the pressure ratio demanded by the engine at the delivered mass flow, so the operating point crosses the surge line. Fouling on either the compressor or turbine side reduces efficiency and flow capacity, shifting the matching point toward surge. Correcting the fouling by water washing or mechanical cleaning restores the margin.

Question 4Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

Which statement correctly describes the function of the air cooler (charge air cooler) in a marine diesel engine scavenge system?

  1. It cools the cylinder liner jacket water before returning it to the engine
  2. It cools the scavenge air after compression to increase its density and reduce thermal load on the cylinder Correct answer.
  3. It cools the exhaust gas before the turbocharger turbine to protect the blades
  4. It removes moisture from the scavenge air by condensation only and has no thermal duty

Explanation

The charge air cooler lowers the temperature of air leaving the turbocharger compressor so that its density rises, increasing the mass of air trapped in the cylinder for combustion. The cooler thermal load also lowers peak combustion temperatures, reducing thermal stress and NOx formation. Condensate removal is a by-product, not the primary purpose.

Question 5Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

A four-stroke auxiliary diesel generator shows a steadily falling lube oil pressure on the local gauge while the running engine continues to operate normally otherwise. Which action should the watchkeeper take first?

  1. Switch to the standby generator only after the next scheduled watch change
  2. Increase the lube oil temperature setpoint to reduce viscosity
  3. Cross-check the pressure with the remote gauge and a manual reading, then trip the engine if low pressure is confirmed Correct answer.
  4. Stop the engine immediately without further checks

Explanation

Falling oil pressure threatens bearing integrity, but a single gauge reading may be faulty, so confirming with an independent measurement is the correct first step. If low pressure is confirmed, the engine must be stopped or tripped to prevent bearing damage. Delaying action or altering oil temperature does not address the underlying loss of pressure.

Question 6Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

In a shell-and-tube lube oil cooler, which condition most reduces the cooler's effectiveness while the cooling water flow and oil flow remain unchanged?

  1. A small reduction in cooling water pump discharge pressure
  2. A slight rise in cooling water inlet temperature
  3. An increase in oil viscosity due to colder oil
  4. Scale and fouling build-up on the tube surfaces Correct answer.

Explanation

Scale and fouling add a thermal resistance layer on the tube surfaces, reducing the overall heat transfer coefficient and therefore the cooler's capacity to remove heat. With flows unchanged, the oil outlet temperature rises. The other options either change the driving temperature difference or are secondary effects, not a fouling-driven loss of effectiveness.

Question 7Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

Which is the primary purpose of the fuel oil separator in the engine room fuel treatment system?

  1. To remove water and solid contaminants from the fuel before it reaches the engine Correct answer.
  2. To measure the fuel oil flow rate for consumption records
  3. To raise the fuel oil temperature to injection viscosity
  4. To blend heavy fuel oil with distillate to achieve the required sulphur content

Explanation

The fuel oil separator uses centrifugal force in a rotating bowl to remove water and solid impurities from the fuel, protecting pumps, filters, and injection equipment. Heating is used to reduce viscosity and improve separation efficiency but is not the separator's purpose. Flow measurement is done by a flowmeter, not the separator.

Question 8Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

A main engine fuel injection pump delivers fuel at the correct pressure but the engine runs rough with one unit showing a late combustion peak on the indicator diagram. Which fault is most consistent with these symptoms?

  1. A sticking fuel pump plunger causing delayed spill Correct answer.
  2. A worn fuel injector nozzle with a blocked or eroded spray hole
  3. A leaking fuel valve cooling water connection
  4. A blocked fuel oil return line from the high-pressure pump

Explanation

A sticking plunger delays the build-up of injection pressure and therefore retards the start of injection, producing a late combustion peak on the indicator card. The pump still reaches delivery pressure once the plunger moves, so pressure alone appears normal. Worn nozzles typically cause poor atomisation and smoke rather than a late peak.

Question 9Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

During manoeuvring, the main engine must be reversed repeatedly. Which statement about the starting air system is correct?

  1. Starting air is admitted only to the number one unit because it is the reference cylinder
  2. Starting air is used only to supply the control air circuit and does not rotate the engine
  3. Starting air is admitted to all cylinders simultaneously to overcome the static friction of the shafting
  4. Starting air is admitted to the cylinders in firing order to rotate the engine in the required direction Correct answer.

Explanation

In an air-start system, the starting air distributor admits air to each cylinder in the correct firing order and at the appropriate crank angle so that the engine accelerates in the selected direction. Admitting air to all cylinders at once would create opposing forces and could not produce controlled rotation. The direction is set by the distributor timing, not by a single reference cylinder.

Question 10Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

A steering gear hydraulic system shows a slow loss of oil level in the header tank with no visible external leak. Which internal fault is most likely?

  1. A blocked suction filter causing cavitation in the pump
  2. A faulty pressure gauge giving a false high reading
  3. A leaking relief valve passing oil back to the return line
  4. A worn ram seal allowing oil to bypass internally between the two sides of the actuator Correct answer.

Explanation

Internal bypass across a worn ram or actuator seal allows oil to pass from the high-pressure side to the low-pressure side without appearing as an external leak, so the header tank level falls as oil is displaced. Relief valve passing usually shows as heat and reduced pressure rather than a level loss. A blocked suction filter and a faulty gauge do not consume oil.

Question 11Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

Which safety device is required on a main propulsion engine to protect against overspeed?

  1. A thrust bearing temperature alarm
  2. A scavenge air space temperature alarm
  3. A crankcase oil mist detector
  4. A governor with an independent overspeed trip that cuts off fuel Correct answer.

Explanation

Overspeed protection is provided by a governor that regulates speed and a separate overspeed trip that independently cuts off fuel if the set speed is exceeded. The trip must be independent of the governor so that a governor failure does not also disable the protection. Oil mist detection and temperature alarms protect against other hazards and do not limit speed.

Question 12Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

A ship's main engine crankcase oil mist detector alarm activates. What is the correct immediate response?

  1. Open the crankcase doors to ventilate the space and clear the mist
  2. Reduce engine load to slow speed and continue monitoring the alarm
  3. Stop the engine, cut off fuel, and prevent starting until the cause has been investigated Correct answer.
  4. Increase crankcase ventilation to dilute the mist below the alarm threshold

Explanation

Oil mist in the crankcase indicates a hot spot that can lead to a crankcase explosion, so the engine must be stopped and fuel cut off to remove the ignition source. The crankcase must not be opened until it has cooled, because admitting air to a hot crankcase can cause an explosion. Ventilation or load reduction does not remove the hazard.

Question 13Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

Which statement best describes the role of the thrust bearing in a main propulsion shafting system?

  1. It supports the vertical weight of the propeller shaft between bearings
  2. It provides the watertight seal where the shaft passes through the hull
  3. It transmits the propeller thrust to the ship's hull while allowing the shaft to rotate Correct answer.
  4. It absorbs torsional vibration from the engine and prevents it reaching the propeller

Explanation

The thrust bearing takes the axial force generated by the propeller and transmits it to the hull structure through the thrust block, while permitting the shaft to rotate freely. Vertical support is provided by line shaft bearings, sealing by the stern tube gland, and torsional vibration is addressed by detuning or dampers. These are separate functions.

Question 14Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

A centrifugal pump in the engine room loses suction and delivers no flow shortly after start-up. Which cause is most likely?

  1. A worn impeller reducing discharge head
  2. A partially closed discharge valve
  3. Excessive discharge pressure from a downstream restriction
  4. Air trapped in the suction line or pump casing Correct answer.

Explanation

Centrifugal pumps cannot self-prime, so air trapped in the suction line or casing prevents the pump from developing suction and it loses flow. The pump must be primed and the suction line vented. A worn impeller reduces head but does not usually stop flow entirely, and a closed discharge valve would cause the pump to run at shut-off head rather than lose suction.

Question 15Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

In a marine auxiliary boiler, which condition would cause the burner to trip on flame failure shortly after ignition?

  1. A low feedwater temperature entering the economiser
  2. A slightly high boiler water level in the gauge glass
  3. A flame scanner that is dirty or misaligned so it cannot detect the flame Correct answer.
  4. A small increase in the fuel oil supply pressure

Explanation

The flame scanner must reliably detect the flame; if the lens is dirty or the scanner is misaligned it may fail to see the flame and the burner management system will trip on flame failure. The trip is a safety response to a perceived loss of flame. Water level, feedwater temperature, and a modest fuel pressure rise do not cause flame failure trips.

Question 16Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

Which statement about the operation of a marine fresh water generator is correct?

  1. It distils seawater at atmospheric pressure using exhaust gas heat only
  2. It evaporates seawater under vacuum so that boiling occurs at a temperature well below 100 degrees Celsius Correct answer.
  3. It freezes seawater and separates the ice from the brine to produce fresh water
  4. It uses reverse osmosis membranes to remove salt from seawater

Explanation

A vacuum fresh water generator uses an ejector or pump to maintain low pressure in the evaporator shell so that seawater boils at a temperature well below 100 degrees Celsius, typically around 40 to 60 degrees Celsius. The vapour is then condensed to produce distillate. Reverse osmosis is a separate technology, and freezing is not used on board.

Question 17Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

A purifier bowl begins to vibrate heavily and the vibration alarm sounds shortly after start-up. Which action is most appropriate?

  1. Increase the feed rate to stabilise the bowl
  2. Reduce the bowl speed setpoint and continue operation
  3. Loosen the bowl lock ring to relieve the vibration
  4. Stop the purifier, allow it to run down, and investigate for incorrect bowl assembly or sludge imbalance Correct answer.

Explanation

Heavy vibration in a centrifugal purifier usually indicates an unbalanced bowl caused by incorrect assembly, missing parts, or uneven sludge loading. The machine must be stopped and allowed to coast down before inspection, because opening or adjusting a spinning bowl is extremely dangerous. Increasing feed or loosening parts would worsen the condition.

Question 18Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

Which parameter is the most direct indicator of the condition of the main engine cylinder liner surface during operation?

  1. The jacket cooling water header pressure
  2. The fuel oil supply pressure at the engine inlet
  3. The cylinder liner wall temperature trend compared with sister units Correct answer.
  4. The scavenge air receiver pressure

Explanation

Cylinder liner wall temperature reflects the balance between heat input from combustion and heat removal by the cooling water and oil, so a rising trend relative to sister units signals wear, fouling, or poor lubrication. Scavenge air pressure, fuel supply pressure, and jacket water header pressure reflect system conditions rather than the liner surface condition. Trending the liner temperature is the standard diagnostic.

Question 19Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

Which is the correct purpose of the air vessel (air bottle) fitted on the discharge side of a reciprocating pump?

  1. To act as a safety relief in case the discharge valve is closed
  2. To increase the pump's volumetric efficiency by pre-compressing the liquid
  3. To store compressed air for starting the engine
  4. To smooth the pulsating flow and reduce water hammer in the discharge line Correct answer.

Explanation

A reciprocating pump delivers liquid in pulses, and the air vessel acts as a cushion that absorbs the pulsations, giving a steadier discharge flow and reducing pressure surges and water hammer. It is not a starting air reservoir and does not replace a relief valve. Its effect is on flow smoothing, not on volumetric efficiency.

Question 20Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

During a main engine manoeuvring sequence the engine fails to start on air in the astern direction but starts normally ahead. Which component is the most likely cause?

  1. The main air receiver drain valve left open
  2. The fuel injection pump rack setting
  3. The starting air distributor timing or the reversing linkage setting for the astern position Correct answer.
  4. The starting air compressor discharge valve

Explanation

Directional starting depends on the starting air distributor admitting air at the correct crank angle for the selected direction, and on the reversing linkage setting the distributor and fuel camshaft correctly. If ahead starting works but astern does not, the astern setting of the distributor or reversing gear is the most likely fault. Compressor and receiver faults would affect both directions.

Question 21Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

Which statement about the operation of a marine incinerator is correct?

  1. It is designed primarily to generate steam for the auxiliary boiler
  2. It may burn any waste oil and garbage without restriction as long as the ship is at sea
  3. It may burn sludge oil and solid waste, but plastics containing PVC should not be burned because of corrosive and toxic emissions Correct answer.
  4. It must be operated only in port where shore reception facilities are available

Explanation

A shipboard incinerator is designed to burn approved waste such as sludge oil and solid garbage, but materials containing PVC and other halogenated plastics must be excluded because they produce corrosive hydrogen chloride and toxic emissions that damage the incinerator and violate MARPOL requirements. Operation is subject to Annex VI and ship-specific procedures, not unrestricted.

Question 22Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

A main engine indicator diagram shows combustion pressure significantly lower than normal on one unit, with a normal compression pressure. Which fault is most consistent with this reading?

  1. A leaking exhaust valve seat
  2. A blocked scavenge air port
  3. Excessive cylinder lubricating oil feed
  4. A worn or sticking fuel injector needle causing reduced fuel delivery Correct answer.

Explanation

Normal compression pressure confirms that the cylinder is sealing correctly, so the low peak combustion pressure points to reduced fuel energy release. A worn or sticking injector needle reduces fuel delivery and produces a low peak. A leaking exhaust valve or blocked scavenge port would lower compression pressure as well.

Question 23Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

Which is the main function of the jacket cooling water system on a large marine diesel engine?

  1. To provide cooling water for the accommodation air conditioning units
  2. To remove heat from the cylinder liners and cylinder heads to keep metal temperatures within safe limits Correct answer.
  3. To cool the fuel oil to the correct injection temperature
  4. To condense the exhaust gas from the turbocharger

Explanation

The jacket cooling water system circulates treated fresh water through the cylinder liners, cylinder heads, and sometimes the turbocharger, removing heat to keep metal temperatures and thermal stresses within design limits. Fuel oil is heated, not cooled, for injection. Air conditioning uses a separate chilled water system, and exhaust gas is not condensed.

Question 24Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

During a sea passage the main engine exhaust gas boiler (economiser) shows a falling steam output while the engine load is steady. Which cause is most likely?

  1. Soot and scale fouling on the gas side reducing heat transfer Correct answer.
  2. A slight increase in the engine room ambient temperature
  3. A change in the fuel oil viscosity at the settling tank
  4. A small rise in the boiler feedwater pump discharge pressure

Explanation

With engine load steady, the exhaust gas heat available is constant, so falling steam output points to reduced heat transfer in the economiser. Soot deposits on the gas side and scale on the water side both add thermal resistance. Soot blowing and water treatment checks are the appropriate response. Ambient temperature and feed pump pressure do not change the heat available.

Question 25Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

Which practice is correct when taking over an engine room watch from the outgoing engineer?

  1. Accept the watch verbally and begin rounds immediately without reviewing the log
  2. Wait for the chief engineer to arrive before accepting the watch
  3. Read the logbook, note any machinery abnormalities and outstanding work, and physically check critical parameters before accepting Correct answer.
  4. Accept the watch only if all machinery is running normally

Explanation

A proper watch handover requires reviewing the logbook and any outstanding defects, then physically verifying critical parameters such as levels, pressures, and temperatures before accepting responsibility. This ensures the incoming engineer is aware of abnormal conditions and ongoing work. Verbal acceptance alone or waiting for the chief engineer is not the standard procedure.

Question 26Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

On a large two-stroke marine diesel engine, what is the primary function of the scavenge air receiver?

  1. It supplies starting air directly to the air start valve during manoeuvring
  2. It acts as a silencing chamber for the exhaust gas pulse before the turbocharger turbine
  3. It separates water and oil mist from the crankcase ventilation gases
  4. It stores compressed air at charge pressure and distributes it uniformly to the cylinder inlet ports during scavenging Correct answer.

Explanation

The scavenge air receiver is the volume between the turbocharger compressor outlet and the cylinder scavenge ports; it damps pressure pulsations so each cylinder receives air at an even charge pressure. It also gives a reserve of air that helps the engine pick up load quickly. It is not part of the starting air or exhaust systems.

Question 27Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

A main engine cylinder unit shows a normal compression pressure but the firing pressure is markedly low. Which fault is the most likely cause?

  1. A worn piston ring set
  2. A faulty fuel injector nozzle with poor atomisation Correct answer.
  3. A blocked scavenge air port
  4. A leaking exhaust valve seat

Explanation

If compression pressure is normal, the cylinder is sealing well, so the shortfall must be in the fuel energy released. A defective injector nozzle gives poor atomisation and late or incomplete combustion, lowering the peak firing pressure while compression remains intact. Valve, ring and scavenge port faults would normally depress compression pressure as well.

Question 28Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

What is the main purpose of the turning gear interlock on a large marine propulsion diesel engine?

  1. To lock the camshaft in the ahead position before starting
  2. To limit the engine speed during prolonged slow running in port
  3. To hold the crankshaft against rotation while the piston is withdrawn
  4. To prevent the engine from being started on air while the turning gear is still engaged Correct answer.

Explanation

The turning gear interlock is a safety arrangement that blocks the starting air supply, or otherwise inhibits starting, unless the turning gear is fully disengaged. Starting the engine with the gear engaged would destroy the turning gear and injure personnel. The interlock has no speed-limiting or camshaft-locking role.

Question 29Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

In a main engine fuel injection system, what is the function of the fuel high-pressure pipe between the pump and the injector?

  1. It maintains a constant residual pressure in the injector cooling circuit
  2. It circulates fuel through the injector body to keep the nozzle cool
  3. It returns surplus fuel from the injector to the settling tank
  4. It delivers a metered quantity of fuel at injection pressure with minimum pressure distortion Correct answer.

Explanation

The high-pressure pipe carries the metered charge from the injection pump to the injector and must transmit the pressure wave with as little damping or reflection as possible so injection timing and quantity stay correct. Its length and stiffness are therefore controlled during installation. Surplus fuel return and cooling flows use separate low-pressure lines.

Question 30Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

A ship is running at full sea load when the main engine turbocharger begins to race and the scavenge air pressure falls. Which condition best explains this behaviour?

  1. A fouled turbine nozzle ring combined with a leaking air cooler
  2. A cracked piston crown on one unit
  3. A sudden partial blockage of the charge air cooler on the water side
  4. A broken exhaust valve spindle on one cylinder Correct answer.

Explanation

A broken exhaust valve spindle allows combustion gas to escape into the exhaust receiver without doing work on the piston, so the turbine receives a larger, hotter gas flow and speeds up while the cylinder charge and scavenge pressure drop. This mismatch of high turbocharger speed with low scavenge pressure is characteristic of a failed exhaust valve. Cooling water or air-side restrictions would not make the turbocharger race.

Question 31Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

Which statement correctly describes the purpose of the jacket cooling water system on a large marine diesel engine?

  1. It removes heat from the cylinder liners and covers to keep metal temperatures within safe limits Correct answer.
  2. It cools the scavenge air before it enters the cylinder ports
  3. It provides cooling for the fuel injection pumps and the camshaft bearings
  4. It condenses the exhaust steam from the turbocharger turbine

Explanation

The jacket cooling water circulates through the cylinder liners, cylinder covers and sometimes the exhaust valve cages to carry away heat and hold metal temperatures within design limits. This protects the lubricating oil film and limits thermal stressing of the components. Charge air cooling and fuel pump cooling are handled by separate circuits.

Question 32Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

During a manoeuvring sequence, the main engine repeatedly fails to start on air although the starting air receiver pressure is normal. Which cause should be investigated first?

  1. A high exhaust gas temperature on one unit
  2. A leaking starting air valve on one cylinder head
  3. Low lubricating oil pressure in the main bearing header
  4. The starting air distributor timing being out of adjustment Correct answer.

Explanation

If receiver pressure is adequate but the engine will not turn on air, the air must not be reaching the cylinders at the right moment. The starting air distributor pilot valve timing is a common cause, since incorrect timing means the air start valves open at the wrong crank angle and the engine cannot be turned. Leaking air start valves usually cause late or uneven firing rather than total failure to start.

Question 33Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

What is the main function of the thrust block in a marine propulsion shafting system?

  1. It aligns the intermediate shaft with the stern tube bearing
  2. It absorbs torsional vibration from the engine crankshaft
  3. It supports the weight of the propeller shaft between bearings
  4. It transmits the propeller thrust to the ship's hull structure Correct answer.

Explanation

The thrust block carries the axial force produced by the propeller and transmits it to the hull through its foundation, so the shafting does not move fore and aft. The thrust bearing pads run in an oil film and are designed for this axial load. Shaft weight and alignment are handled by the line bearings and the sterntube bearing.

Question 34Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

A centrifugal pump in the engine room loses suction and delivers no flow shortly after start-up. Which cause is the most likely?

  1. The impeller is worn at the wear rings
  2. The discharge valve is fully open
  3. The pump is running at a speed above its rated value
  4. The pump is air-bound because the suction line was not properly primed Correct answer.

Explanation

A centrifugal pump cannot self-prime, so if air remains in the suction line or casing after start-up it loses suction and delivers no flow. This is the classic air-bound condition and is corrected by priming and venting. Wear ring wear and overspeed reduce performance but do not usually cause complete loss of flow immediately after start-up.

Question 35Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

A purifier bowl begins to vibrate heavily shortly after start-up and the vibration alarm sounds. Which action is most appropriate?

  1. Reduce the bowl speed to the lowest possible value
  2. Increase the feed rate to settle the bowl
  3. Stop the purifier, clean the bowl and check for sludge deposits and correct assembly Correct answer.
  4. Continue running and monitor the vibration trend

Explanation

Heavy bowl vibration shortly after start-up usually indicates an out-of-balance condition, often caused by uneven sludge deposits or incorrect bowl assembly. The safe response is to stop the machine and inspect and clean the bowl. Continuing to run or increasing feed risks damage to the bearings and the bowl.

Question 36Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

What is the correct purpose of the air vessel fitted on the discharge side of a reciprocating pump?

  1. To reduce flow pulsation and give a steadier discharge Correct answer.
  2. To measure the discharge pressure of the pump
  3. To act as a suction reservoir to prime the pump
  4. To store liquid for use during pump stoppage

Explanation

A reciprocating pump delivers liquid in pulses, and the air vessel on the discharge side acts as a cushion that absorbs the peaks and releases liquid during the troughs. This smooths the flow and reduces pressure surges in the discharge line. The vessel contains compressed air, not a liquid store, and does not measure pressure.

Question 37Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

During a sea passage the main engine exhaust gas boiler shows falling steam output while engine load and exhaust gas temperature remain steady. Which cause is most likely?

  1. The feed water temperature has fallen
  2. The steam demand from the ship's service system has increased
  3. The boiler water level is being carried too high
  4. Soot deposits have built up on the gas-side heating surfaces Correct answer.

Explanation

With engine load and exhaust gas temperature steady, the heat available to the boiler has not changed, so falling output points to reduced heat transfer. Soot on the gas side acts as an insulating layer and is the classic cause, corrected by soot blowing. A change in feed water temperature or steam demand would show as a change in the boiler's operating conditions rather than a steady-state loss.

Question 38Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

Which practice is correct when an engineer takes over an engine room watch from the outgoing engineer?

  1. Wait until the next alarm occurs before inspecting the machinery spaces
  2. Take over only after the chief engineer has personally confirmed the watch change
  3. Accept the watch only after a joint round and a briefing on the machinery condition and any outstanding defects Correct answer.
  4. Sign the log book and take over immediately to avoid delaying the outgoing engineer

Explanation

A proper watch handover requires a joint inspection of the machinery spaces and a briefing on running conditions, abnormal readings, ongoing work and outstanding defects. This ensures the relieving engineer knows the state of the plant before accepting responsibility. Signing over without this check or waiting for an alarm defeats the purpose of the handover.

Question 39Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

On a large two-stroke marine diesel engine, what is the primary function of the crosshead in the running gear arrangement?

  1. It carries the axial thrust of the propeller shaft and transmits it to the engine bedplate.
  2. It seals the combustion space from the scavenge air space and wipes oil from the liner surface.
  3. It guides the piston rod so that the side thrust from the connecting rod is taken by the guide shoes instead of the piston and liner. Correct answer.
  4. It converts the reciprocating motion of the piston into rotary motion of the crankshaft.

Explanation

In a crosshead engine the piston rod is rigidly connected to the crosshead, and the crosshead shoes slide in vertical guides. This arrangement absorbs the transverse component of the connecting rod force at the guides, so the piston moves axially with minimal side thrust and liner wear is reduced. It also allows the piston to run with a short skirt and permits effective sealing of the scavenge space.

Question 40Marine Engineering Knowledge (Main Propulsion and Auxiliary Machinery)

During a sea passage a main engine cylinder unit shows a normal compression pressure, but the exhaust gas temperature after the unit is abnormally high and the turbocharger is surging. Fuel rack setting and injection timing are confirmed correct. Which fault best explains these symptoms?

  1. Worn piston rings allowing blow-by past the piston
  2. A partly seized or sticking fuel injector needle causing late, prolonged after-burning Correct answer.
  3. Leaking exhaust valve causing loss of compression in that unit
  4. A restricted scavenge air cooler on the affected unit only

Explanation

Normal compression pressure rules out major leakage past valves or rings, so the fault lies in fuel delivery or combustion quality. A sticking or partly seized injector needle disturbs atomisation and delays the end of injection, producing after-burning that raises exhaust temperature and can trigger turbocharger surging from unstable cylinder output. The injector should be changed and the unit checked before continuing at full load.

Question 41Marine Electrical, Electronic and Control Engineering

On a 60 Hz three-phase alternator, the line voltage measured between any two output terminals is 440 V and the current in each line is 100 A at a power factor of 0.8 lagging. What is the approximate three-phase active power delivered?

  1. About 61 kW Correct answer.
  2. About 44 kW
  3. About 35 kW
  4. About 76 kW

Explanation

For a balanced three-phase load the active power is P = √3 × U_line × I_line × cos φ. Substituting 1.732 × 440 × 100 × 0.8 gives approximately 61 kW. The √3 factor is required because line voltage and line current are used rather than phase values.

Question 42Marine Electrical, Electronic and Control Engineering

In a ship's lead-acid battery installation, which condition indicates that a cell is approaching a fully discharged state during a discharge test?

  1. The electrolyte specific gravity falls close to its minimum specified value Correct answer.
  2. The terminal voltage rises above the float voltage
  3. The charging current increases sharply
  4. The electrolyte temperature falls below ambient

Explanation

During discharge the sulphuric acid is consumed and the electrolyte specific gravity falls steadily toward its lower limit. Specific gravity is therefore a reliable indicator of state of charge for lead-acid cells. Voltage also falls, but the specific gravity limit is the definitive manufacturer criterion for end of discharge.

Question 43Marine Electrical, Electronic and Control Engineering

A marine diesel generator's automatic voltage regulator (AVR) holds the alternator terminal voltage constant. What is the primary effect of the AVR on the reactive power sharing between two generators operating in parallel?

  1. It adjusts excitation to control active load sharing
  2. It has no influence on load sharing of any kind
  3. It adjusts excitation to control reactive load sharing Correct answer.
  4. It adjusts prime-mover speed to control reactive load

Explanation

Reactive power sharing between paralleled synchronous generators is governed by field excitation, which the AVR controls. The prime-mover governor, by contrast, controls active power sharing through speed/frequency droop. Coordinating AVR voltage droop settings therefore balances reactive load.

Question 44Marine Electrical, Electronic and Control Engineering

A Class B fire is burning in a machinery space. Which extinguishing medium is the correct primary choice according to standard marine fire-fighting practice?

  1. Carbon dioxide only for electrical fires
  2. Sand only
  3. Foam or dry chemical powder Correct answer.
  4. Water spray from a hydrant

Explanation

Class B fires involve flammable liquids, and foam blankets the surface to exclude oxygen while dry powder interrupts the flame chemistry. Water is generally unsuitable because it can spread burning liquid. The correct medium must match the fuel class for effective and safe extinguishing.

Question 45Marine Electrical, Electronic and Control Engineering

A three-phase induction motor driving a seawater pump is started direct-on-line. Which starting characteristic is the main reason DOL starting is restricted for large motors on a limited ship's supply?

  1. The starting current can be five to eight times rated current Correct answer.
  2. The starting torque is zero
  3. The motor speed overshoots synchronous speed
  4. The power factor becomes leading during start

Explanation

DOL starting draws a large inrush current, typically five to eight times full-load current, which causes voltage dips on a limited-capacity ship's bus. Reduced-voltage or soft starters limit this inrush. The high current, not torque or power factor, is the limiting factor.

Question 46Marine Electrical, Electronic and Control Engineering

Which instrument is used on board to measure the insulation resistance of a 440 V distribution circuit and why must it be used with the circuit isolated?

  1. A clamp ammeter, because it measures leakage current directly
  2. A multimeter on the resistance range, because it uses a low test voltage
  3. A megohmmeter, because it applies a high test voltage that could damage equipment or endanger personnel if the circuit is live Correct answer.
  4. A wattmeter, because it measures insulation power loss

Explanation

A megohmmeter applies a high DC test voltage (commonly 500 V or 1000 V) to measure insulation resistance in megohms. The circuit must be isolated and discharged because the test voltage could damage sensitive electronics and endanger personnel. A low-voltage multimeter cannot reliably assess insulation quality.

Question 47Marine Electrical, Electronic and Control Engineering

In a ship's alarm and monitoring system, what is the function of the dead band (hysteresis) applied to an analogue alarm channel?

  1. It delays the alarm indefinitely until manually reset
  2. It prevents the alarm from chattering when the measured value fluctuates around the set point Correct answer.
  3. It converts the analogue signal to a digital value
  4. It increases the sensor's measuring range

Explanation

Dead band, or hysteresis, requires the measured value to move a defined amount past the set point before the alarm clears. This prevents rapid on/off cycling when the signal hovers near the threshold. It does not change range or perform analogue-to-digital conversion.

Question 48Marine Electrical, Electronic and Control Engineering

A programmable logic controller (PLC) on a vessel scans its program cyclically. Which sequence describes a typical scan cycle?

  1. Read inputs, update outputs, execute the program logic
  2. Read inputs, execute the program logic, update outputs Correct answer.
  3. Update outputs, read inputs, execute the program logic
  4. Execute the program logic, read inputs, update outputs

Explanation

A PLC scan normally reads all input states into memory, solves the user program using those states, then writes the results to the output modules. This order ensures the program operates on a consistent snapshot of inputs. Output updating after logic execution avoids partial results.

Question 49Marine Electrical, Electronic and Control Engineering

A separately excited DC motor used for a deck winch is controlled by armature voltage. What happens to the motor speed and torque if the field current is accidentally lost while the armature is energised?

  1. The motor reverses direction at constant speed
  2. The motor may overspeed dangerously because the flux collapses and back-EMF falls Correct answer.
  3. The motor stops immediately and safely
  4. The motor speed falls to zero and torque increases

Explanation

In a DC motor the back-EMF is proportional to flux times speed. If field current is lost, flux collapses, back-EMF falls, armature current rises sharply, and the motor can accelerate to a dangerous overspeed. Field-loss protection is therefore essential on separately excited machines.

Question 50Marine Electrical, Electronic and Control Engineering

What is the purpose of the synchronising check relay in a generator circuit breaker closing circuit?

  1. It permits closing only when voltage, frequency and phase angle are within limits Correct answer.
  2. It limits the generator's output current after closing
  3. It disconnects the generator on reverse power
  4. It measures the generator's insulation resistance before closing

Explanation

The synchronising check relay compares the incoming generator voltage with the busbar in magnitude, frequency and phase angle. It allows the breaker close command only when these parameters are within preset limits, preventing severe mechanical and electrical stress. Other protective functions are handled by separate relays.