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Croatia Chief Engineer Officer practice questions

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Question 1Marine Engineering Knowledge and Machinery Operation

During a routine inspection, a chief engineer finds that the main engine fuel oil viscosity at the inlet to the fuel pumps is lower than the manufacturer's specified range. Which immediate action best protects the fuel injection equipment?

  1. Switch to a lower-viscosity distillate fuel without notifying the bridge
  2. Adjust the fuel oil heater to raise the viscosity to the specified range Correct answer.
  3. Increase the fuel oil supply pressure to the injection pumps
  4. Raise the fuel oil temperature at the settling tank to reduce viscosity further

Explanation

Injection pumps and injectors rely on fuel viscosity within a narrow band to maintain lubrication of plungers and correct injection timing and atomisation. If viscosity is too low, the heater output should be adjusted upward to restore the specified range at the pump inlet. Raising temperature further or diluting with distillate worsens lubrication and atomisation control.

Question 2Marine Engineering Knowledge and Machinery Operation

What is the primary purpose of the air receiver in a starting air system for a marine diesel main engine?

  1. To store compressed air at sufficient pressure and volume for repeated engine starting Correct answer.
  2. To provide pneumatic pressure for the fuel valve testing bench
  3. To cool the scavenge air before it enters the cylinders
  4. To supply combustion air to the turbocharger inlet

Explanation

The starting air receiver stores compressed air so that the engine can be started repeatedly without waiting for the compressor to rebuild pressure. Classification rules require enough capacity for a specified number of consecutive starts. It does not feed combustion air, cool scavenge air, or serve as a testing bench supply.

Question 3Marine Engineering Knowledge and Machinery Operation

A marine auxiliary boiler shows a rising water level in the gauge glass while the feedwater regulating valve is closed and steam demand is steady. Which fault is most likely?

  1. The feedwater pump has lost suction
  2. The gauge glass lower connection is blocked
  3. The steam demand has suddenly increased
  4. A leak in the internal economiser or a tube is admitting water into the boiler Correct answer.

Explanation

With the feed valve shut and steady steam demand, a rising level indicates water entering the shell from an unintended path. An internal leak from a tube or economiser is the classic cause. Loss of pump suction or increased steam demand would lower the level, and a blocked lower glass connection would give a false low or misleading reading.

Question 4Marine Engineering Knowledge and Machinery Operation

In a four-stroke marine diesel engine, what is the function of the air inlet valve rotator fitted to the exhaust valve spindle?

  1. To increase valve lift at high engine load
  2. To reduce the valve spring compression during opening
  3. To rotate the valve so that it seats evenly and avoids localised hot spots and carbon build-up Correct answer.
  4. To seal the valve guide against exhaust gas leakage

Explanation

Valve rotators turn the exhaust valve slightly with each lift so that the seating face wears and heats uniformly, reducing carbon deposits and localised burning. This extends valve life and maintains a gas-tight seal. They do not change valve lift, spring compression, or guide sealing.

Question 5Marine Engineering Knowledge and Machinery Operation

The oil mist detector on a medium-speed diesel engine alarms during normal operation. What is the correct first response by the engineering watch?

  1. Increase crankcase ventilation to dilute the mist
  2. Add fresh lubricating oil to lower the mist concentration
  3. Reduce load and investigate for a hot spot or bearing distress before considering a shutdown Correct answer.
  4. Reset the detector and continue running at full load

Explanation

An oil mist alarm indicates possible overheating of a bearing or piston, which can lead to a crankcase explosion. The watch should reduce load and investigate immediately, preparing to stop the engine if the condition persists. Resetting, ventilating, or diluting with oil does not remove the ignition source and risks explosion.

Question 6Marine Engineering Knowledge and Machinery Operation

Which statement correctly describes the effect of a partially blocked charge air cooler on main engine operation?

  1. Scavenge air pressure rises and exhaust gas temperature falls
  2. Scavenge air temperature rises and thermal load on the exhaust valves increases Correct answer.
  3. Cylinder liner wear decreases because the air is warmer
  4. Specific fuel consumption improves due to reduced cooling

Explanation

A restricted charge air cooler reduces heat transfer, so scavenge air enters the cylinders hotter and denser air charge is lost. Higher scavenge temperature raises peak combustion and exhaust valve temperatures, increasing thermal stress. It does not raise scavenge pressure or improve fuel consumption.

Question 7Marine Engineering Knowledge and Machinery Operation

What is the purpose of the bursting disc or relief arrangement on a starting air line between the air receiver and the main engine?

  1. To drain condensate from the starting air line
  2. To regulate the starting air pressure supplied to the engine
  3. To silence the noise of air discharge during starting
  4. To protect the line against excessive pressure from a leaking air start valve Correct answer.

Explanation

If an air start valve leaks or sticks, high-pressure combustion gas can enter the starting air line and overpressurise it. The bursting disc or relief valve protects the line from rupture. It is not a drain, pressure regulator, or silencer.

Question 8Marine Engineering Knowledge and Machinery Operation

During manoeuvring, the main engine is required to reverse quickly. Which action best prevents overload of the engine and starting air system?

  1. Bypassing the starting air interlocks to speed up the sequence
  2. Applying full starting air immediately after the telegraph order
  3. Keeping the fuel lever at full ahead while reversing
  4. Allowing the engine to come to a complete stop before admitting starting air in the reverse direction Correct answer.

Explanation

Rapid reversal without allowing the engine to stop can cause excessive torque, high starting air consumption, and mechanical damage. The correct procedure is to stop the engine, then admit starting air in the reverse direction. Full air on a turning engine or bypassing interlocks risks damage and is unsafe.

Question 9Marine Engineering Knowledge and Machinery Operation

Which condition most directly indicates that the lubricating oil in a main engine sump requires replacement or purification?

  1. A rise in total base number above the new oil value
  2. A slight increase in oil level after topping up
  3. A decrease in viscosity with a high water content and insoluble content Correct answer.
  4. A stable viscosity and water content within limits

Explanation

A drop in viscosity combined with high water and insolubles indicates dilution, contamination, or degradation that reduces load-carrying ability. Such oil should be purified or replaced. A stable viscosity with water within limits is normal, and total base number does not rise above new oil unless contaminated.

Question 10Marine Engineering Knowledge and Machinery Operation

A centrifugal purifier is being used to clean main engine fuel oil. What is the effect of increasing the throughput rate beyond the design value?

  1. Improved separation due to higher flow velocity
  2. Higher bowl speed and better sludge removal
  3. No change in separation performance
  4. Reduced separation efficiency because residence time in the bowl is shortened Correct answer.

Explanation

Separation depends on residence time in the bowl; excessive throughput shortens the time for heavy particles and water to migrate to the bowl wall. Efficiency therefore falls and carry-over increases. Flow rate does not increase bowl speed or improve separation.

Question 11Marine Engineering Knowledge and Machinery Operation

Which safety device prevents the main engine from being started while the turning gear is engaged?

  1. The turning gear interlock Correct answer.
  2. The overspeed trip
  3. The crankcase oil mist detector
  4. The scavenge air fire alarm

Explanation

The turning gear interlock blocks starting air or ignition while the turning gear is engaged, preventing catastrophic damage and injury. Overspeed trip limits engine speed, oil mist detection warns of crankcase overheating, and scavenge fire alarms detect fires.

Question 12Marine Engineering Knowledge and Machinery Operation

The main engine exhaust gas boiler is producing insufficient steam while the engine is at normal load. Which cause should be investigated first?

  1. A closed steam stop valve downstream
  2. Excessive feedwater temperature
  3. Low cooling water temperature to the condenser
  4. Soot deposits on the boiler heating surfaces Correct answer.

Explanation

Soot fouling on the gas side acts as insulation and reduces heat transfer, so steam output falls at constant engine load. Soot blowing or water washing restores performance. Feedwater temperature, a closed stop valve, or condenser cooling affect the system differently and do not explain reduced gas-side heat uptake.

Question 13Marine Engineering Knowledge and Machinery Operation

Which parameter is the most reliable indicator of excessive cylinder liner wear in a slow-speed two-stroke engine?

  1. A drop in scavenge air pressure
  2. A steady increase in piston ring groove clearance measured at overhaul
  3. An increasing trend in cylinder liner wear rate from regular gauge measurements Correct answer.
  4. A gradual rise in jacket cooling water outlet temperature

Explanation

Regular liner gauging gives a direct measurement of wear rate and reveals abnormal trends before clearance limits are reached. Jacket water temperature, ring groove clearance, and scavenge pressure are influenced by many factors and are less specific indicators.

Question 14Marine Engineering Knowledge and Machinery Operation

What is the correct action if the main engine fails to start on air because the air start valve is stuck open?

  1. Isolate the starting air supply and repair the valve before further attempts Correct answer.
  2. Continue cranking with the fuel lever in the start position
  3. Open the indicator cocks and keep starting
  4. Increase starting air pressure until the engine turns

Explanation

A stuck-open air start valve allows high-pressure air or combustion gas to pass continuously, creating a hazard and preventing normal starting. The starting air supply must be isolated and the valve repaired. Increasing pressure or continued cranking worsens the risk.

Question 15Marine Engineering Knowledge and Machinery Operation

In a marine refrigeration plant using R404A, what does a high discharge pressure combined with normal suction pressure most likely indicate?

  1. A frosted expansion valve
  2. A leak of refrigerant from the system
  3. A failed compressor suction valve
  4. An overcharged system or restricted condenser cooling Correct answer.

Explanation

High discharge pressure with normal suction pressure points to poor heat rejection at the condenser, such as fouling, restricted cooling water, or overcharge. A refrigerant leak would lower both pressures, and a frosted expansion valve or failed suction valve would primarily affect suction pressure.

Question 16Marine Engineering Knowledge and Machinery Operation

Which statement about the function of the scavenge air receiver in a uniflow-scavenged two-stroke engine is correct?

  1. It provides a reservoir of pressurised air to supply the cylinders during scavenging Correct answer.
  2. It separates water from the lubricating oil
  3. It acts as a silencer for the exhaust gas
  4. It stores fuel for injection during starting

Explanation

The scavenge air receiver holds pressurised air from the turbocharger and delivers it to the scavenge ports during the scavenging period. It does not store fuel, separate oil from water, or silence exhaust gas.

Question 17Marine Engineering Knowledge and Machinery Operation

During a blackout, the emergency generator fails to start automatically. What is the chief engineer's priority action?

  1. Reset all main switchboard breakers simultaneously
  2. Verify that the emergency switchboard is energised from the emergency generator or battery and investigate the start failure Correct answer.
  3. Open the main engine starting air valve
  4. Attempt to restart the main engine immediately

Explanation

Emergency power is essential for steering, lighting, and safety systems, so confirming emergency supply is the priority. The start failure should then be investigated. Restarting the main engine or resetting breakers without understanding the cause risks further loss of power.

Question 18Marine Engineering Knowledge and Machinery Operation

What is the primary reason for maintaining correct piston cooling oil flow in a large marine diesel engine?

  1. To remove heat from the piston crown and prevent overheating and cracking Correct answer.
  2. To cool the scavenge air
  3. To increase the compression ratio
  4. To lubricate the turbocharger bearings

Explanation

Piston cooling oil removes heat absorbed by the crown from combustion, keeping metal temperatures within safe limits and preventing cracking and carbon deposits. It does not change compression ratio, lubricate turbocharger bearings, or cool scavenge air.

Question 19Marine Engineering Knowledge and Machinery Operation

A fuel oil separator is discharging sludge continuously into the sludge tank at an abnormal rate. Which cause is most likely?

  1. The separator is running at reduced throughput
  2. The bowl is incorrectly assembled or the gravity disc is too small Correct answer.
  3. The fuel oil temperature is too high
  4. The sludge tank is being emptied too frequently

Explanation

Continuous heavy sludge discharge suggests incorrect bowl assembly or an undersized gravity disc, causing the water seal to be lost and oil to escape with sludge. Excessive temperature can affect separation but is not the primary cause of abnormal sludge volume, and throughput or tank emptying do not create the fault.

Question 20Marine Engineering Knowledge and Machinery Operation

Which document must be consulted to determine the correct tightening sequence and torque for a main engine cylinder head?

  1. The ship's stability booklet
  2. The oil record book
  3. The cargo securing manual
  4. The engine manufacturer's maintenance manual and instruction book Correct answer.

Explanation

Cylinder head bolt tightening follows the engine builder's specified sequence and torque to ensure even gasket loading and avoid distortion. Stability, oil record, and cargo securing documents do not contain machinery assembly data.

Question 21Marine Engineering Knowledge and Machinery Operation

During operation, a main engine turbocharger begins to surge repeatedly at high load. Which action is most appropriate?

  1. Increase fuel index to push through the surge region
  2. Ignore the surge if exhaust temperatures remain within limits
  3. Open the turbocharger washing water valve immediately
  4. Reduce load and investigate air-side fouling, nozzle ring condition, or exhaust restrictions Correct answer.

Explanation

Surge indicates a mismatch between compressor and turbine performance, often from fouling, damaged nozzle rings, or exhaust restriction. Reducing load protects the turbocharger while the cause is investigated. Increasing fuel or ignoring the symptom risks damage to bearings and blades.

Question 22Marine Engineering Knowledge and Machinery Operation

What is the correct procedure before entering a main engine crankcase for inspection after shutdown?

  1. Open the crankcase doors immediately to cool the space
  2. Allow the engine to cool, isolate starting air, and ensure the crankcase is ventilated and tested for safe atmosphere Correct answer.
  3. Enter with a torch while the engine is still warm to save time
  4. Run the turning gear while personnel are inside

Explanation

Crankcase entry requires the engine to cool, starting air and turning gear to be isolated, and the space to be ventilated and tested for oxygen and explosive atmosphere. Immediate entry or running the turning gear with personnel inside is dangerous.

Question 23Marine Engineering Knowledge and Machinery Operation

In a hydraulic steering gear system, what does a rapid, repeated operation of the steering gear relief valve indicate?

  1. Mechanical obstruction or excessive load in the steering gear system Correct answer.
  2. Low hydraulic oil level only
  3. Correct adjustment of the relief valve
  4. Normal operation during heavy weather

Explanation

Frequent lifting of the relief valve means the system is reaching its pressure limit, usually due to mechanical obstruction, rudder loading beyond design, or a fault in the gear. It is not normal and should be investigated. Low oil level alone would not cause repeated relief valve operation.

Question 24Marine Engineering Knowledge and Machinery Operation

Which measure best reduces the risk of scavenge space fires in a two-stroke diesel engine?

  1. Maintaining correct piston ring condition and avoiding excessive cylinder oil carry-over Correct answer.
  2. Operating with the scavenge drains closed
  3. Increasing cylinder oil feed rate beyond the manufacturer's recommendation
  4. Reducing scavenge air pressure

Explanation

Scavenge fires are fuelled by oil and carbon deposits in the scavenge space, often from worn rings or excessive cylinder oil. Keeping rings in good condition and controlling oil feed reduces deposits. Over-lubrication, closed drains, or low scavenge pressure increase risk or impair detection.

Question 25Marine Engineering Knowledge and Machinery Operation

A marine diesel generator is running with a gradually rising exhaust gas temperature on one cylinder while other cylinders remain normal. Which fault is most likely?

  1. A clogged air filter on the engine room ventilation
  2. A general overload of the generator
  3. A faulty fuel injector or incorrect injection timing on that cylinder Correct answer.
  4. Low cooling water temperature to the engine

Explanation

A single-cylinder exhaust temperature deviation points to a cylinder-specific fault such as a defective injector, poor atomisation, or incorrect timing. General overload or cooling faults would affect all cylinders, and ventilation filter fouling affects the whole engine.

Question 26Marine Engineering Knowledge and Machinery Operation

Under SOLAS II-1, a periodically unattended machinery space must be arranged so that a failure of any one item of control equipment does not cause a hazardous condition. Which design feature most directly satisfies this requirement for the main engine remote control system?

  1. An automatic telephone link between the bridge and the engine control room
  2. A duplicated alarm panel on the bridge showing all engine parameters
  3. A fail-safe arrangement that brings the engine to a safe speed and pitch condition on loss of control signal Correct answer.
  4. A manual override that allows the bridge to bypass all engine safety interlocks

Explanation

The periodically unattended machinery space concept requires that loss of control, alarm or power does not create a hazard, so the propulsion control must revert to a safe condition automatically. This fail-safe philosophy is the core of the SOLAS II-1 requirements for unmanned machinery spaces. Alarms and communications support the concept but do not by themselves prevent a hazardous condition.

Question 27Marine Engineering Knowledge and Machinery Operation

A slow-speed two-stroke main engine shows a rising exhaust gas temperature on one unit while the fuel index and other units remain normal, and the unit's compression pressure is low. Which fault is most consistent with these readings?

  1. Excessive fuel injection quantity from a worn plunger in the fuel pump
  2. Partially blocked scavenge air port reducing air supply to that unit
  3. Incorrect fuel valve opening pressure set too low
  4. Leaking exhaust valve allowing combustion gas to escape during compression Correct answer.

Explanation

A leaking exhaust valve lets charge air escape during compression, lowering compression pressure and combustion quality, so that unit burns poorly and exhaust temperature rises while fuel index remains normal. Fuel pump faults would normally change the fuel index, and scavenge port blockage affects all units sharing the receiver. Injection pressure faults change the combustion pattern but not compression pressure.

Question 28Marine Engineering Knowledge and Machinery Operation

During a routine inspection the chief engineer finds the main engine lubricating oil sump level rising steadily with no external leakage. Which cause should be investigated first?

  1. Excessive oil being added by the crew during topping-up
  2. Cooling water leaking into the oil system from a cracked cylinder liner or cooler Correct answer.
  3. A blocked lubricating oil filter causing bypass flow
  4. A worn lubricating oil pump reducing delivery pressure

Explanation

A rising sump level with no external leak points to contamination, most commonly water from a cracked liner, leaking cooler tube or defective seal. Water ingress dilutes the oil and can cause bearing damage, so this must be investigated immediately. Pump wear and filter blockage cause pressure changes, not increased volume.

Question 29Marine Engineering Knowledge and Machinery Operation

A main engine cylinder liner shows a pronounced 'clover leaf' wear pattern with maximum wear at the scavenge port level. Which operating factor is the most probable cause?

  1. Excessive cylinder oil feed rate combined with high liner temperature
  2. Misalignment of the crankshaft causing edge loading on the liner
  3. Poor combustion and inadequate scavenging causing corrosive attack at the port area Correct answer.
  4. Incorrect piston ring groove clearance allowing ring flutter

Explanation

Clover-leaf wear concentrated near the scavenge ports results from corrosive attack by sulphuric acid formed when combustion is poor and the liner surface is cool and wet in that region. Improving combustion quality, scavenging and cylinder oil feed with correct BN oil addresses the cause. Excessive oil feed does not produce this pattern, and mechanical faults give different wear distributions.

Question 30Marine Engineering Knowledge and Machinery Operation

The main engine is running at full sea load when the turbocharger begins to race and the scavenge air pressure fluctuates. Which immediate action is most appropriate?

  1. Trip the main engine immediately by activating the emergency stop
  2. Increase fuel index to maintain ship speed and monitor the turbocharger
  3. Reduce engine load gradually and investigate the turbocharger and scavenge system Correct answer.
  4. Open the turbocharger washing arrangement to clean the turbine blades

Explanation

Racing and fluctuating scavenge pressure indicate unstable turbocharger operation, often from fouling, air leaks or a faulty charge air cooler. Reducing load lowers thermal and mechanical stress and allows controlled investigation. Immediate emergency stopping may cause loss of manoeuvrability, and water washing while running under these conditions risks blade damage.

Question 31Marine Engineering Knowledge and Machinery Operation

Under MARPOL Annex VI, which operational measure best reduces NOx formation from a slow-speed two-stroke main engine already fitted with a selective catalytic reduction system?

  1. Reducing the scavenge air temperature below the dew point
  2. Raising the fuel injection pressure to improve atomisation
  3. Increasing the cylinder oil feed rate to improve ring sealing
  4. Optimising combustion timing and scavenge air ratio to lower peak cylinder temperature Correct answer.

Explanation

Thermal NOx formation depends strongly on peak combustion temperature and residence time, so optimising injection timing and the air-fuel ratio lowers peak temperature and NOx. The SCR system then treats the remaining NOx in the exhaust. Cylinder oil feed and injection pressure affect wear and combustion quality but are not the primary NOx control lever.

Question 32Marine Engineering Knowledge and Machinery Operation

In a ship's oil-fired auxiliary boiler, the burner fails to ignite and the flame scanner does not detect flame. Which interlock action must the burner management system perform?

  1. Reduce the fuel pressure and continue firing at low rate
  2. Keep the fuel valve open and retry ignition repeatedly until flame is established
  3. Open the furnace doors to ventilate manually while fuel is still admitted
  4. Close the fuel oil valve and continue the purge to clear unburnt fuel from the furnace Correct answer.

Explanation

On loss of flame the burner management system must immediately shut off fuel and maintain or complete a purge to remove unburnt fuel before any reignition attempt. This prevents furnace explosions from accumulated fuel. Repeated ignition attempts without purging, or continued fuel admission, create exactly the explosive condition the interlock is designed to prevent.

Question 33Marine Engineering Knowledge and Machinery Operation

A centrifugal fuel oil purifier is being brought back into service after cleaning. Which practice best ensures effective separation of water and solids from heavy fuel oil?

  1. Increase throughput above rated capacity to process the whole settling tank quickly
  2. Reduce the bowl speed to lengthen residence time for better separation
  3. Admit oil at low temperature to reduce viscosity and improve flow through the bowl
  4. Set the correct gravity disc for the fuel density and bring the bowl to full speed before admitting oil Correct answer.

Explanation

Effective separation depends on selecting the gravity disc that matches the fuel density so the water seal is correctly positioned, and on reaching full bowl speed before oil is admitted. Fuel should be heated to reduce viscosity, not cooled, and throughput should not exceed rated capacity. Reducing bowl speed destroys the centrifugal force needed for separation.

Question 34Marine Engineering Knowledge and Machinery Operation

During a steering gear test before departure, the rudder moves more slowly than normal and the hydraulic oil temperature rises. Which fault is most likely?

  1. The hydraulic oil level in the header tank is slightly high
  2. The rudder angle indicator is out of calibration
  3. The emergency steering pump is isolated as required for normal operation
  4. Internal leakage past the ram seals or in the control valve reducing effective flow Correct answer.

Explanation

Slow rudder movement with rising oil temperature indicates energy being lost as heat through internal leakage, typically past ram seals or control valves. This reduces the flow available to move the rams. Indicator calibration and oil level do not cause slow movement, and the emergency pump is normally isolated during routine operation.

Question 35Marine Engineering Knowledge and Machinery Operation

A ship is required to demonstrate that its oily water separator meets the 15 ppm discharge limit. Which operational practice complies with MARPOL Annex I?

  1. Relying on the separator's internal monitor without the automatic stopping device
  2. Recirculating the bilge water until the alarm stops, then discharging without recording
  3. Discharging only at night to reduce visibility of the overboard discharge
  4. Using the 15 ppm bilge alarm with automatic stopping device and recording discharges in the Oil Record Book Correct answer.

Explanation

MARPOL Annex I requires that discharges through the oily water separator pass a 15 ppm bilge alarm and, for ships of 10,000 GT and above, an automatic stopping device, with all operations recorded in the Oil Record Book. Recirculation until the alarm clears and unrecorded discharge are violations. The automatic stopping device is mandatory, not optional.

Question 36Marine Engineering Knowledge and Machinery Operation

A refrigeration plant using R404A shows low suction pressure, high superheat at the compressor suction and frosting at the expansion valve outlet. Which fault best explains these symptoms?

  1. An overcharged system with excess refrigerant in the condenser
  2. A condenser cooling water temperature that is too low
  3. A compressor suction valve stuck fully open
  4. A restricted or blocked expansion valve passing insufficient refrigerant Correct answer.

Explanation

A restricted expansion valve admits too little refrigerant, so suction pressure falls, superheat rises and the small flow flashes to a low temperature, frosting the valve outlet. Overcharge raises discharge pressure and subcooling, not superheat. Low condenser water temperature lowers discharge pressure but does not cause high suction superheat.

Question 37Marine Engineering Knowledge and Machinery Operation

Before starting a main engine after a prolonged stay in port, which check is most important to confirm the cylinder lubrication system is functioning?

  1. Operate the cylinder lubricators manually or by the pre-lubrication cycle and confirm oil delivery to each liner Correct answer.
  2. Run the engine at full load immediately to warm the cylinder oil
  3. Increase the cylinder oil feed rate to maximum for the first hour of running
  4. Drain the cylinder oil service tank to remove any water before starting

Explanation

After a long stop, cylinder surfaces are dry and the lubricators must be proven to deliver oil to each liner before the engine is turned and started. Pre-lubrication or manual operation confirms delivery and prevents scuffing on first firing. Maximum feed rate for an hour is wasteful and not a substitute for proving delivery, and full-load running on a cold engine risks damage.

Question 38Marine Engineering Knowledge and Machinery Operation

An auxiliary diesel generator trips on low lubricating oil pressure while running at 80% load. Which sequence of actions best reflects correct engineering practice?

  1. Increase the lubricating oil pressure setpoint to prevent a repeat trip and continue running
  2. Isolate the low pressure trip and run the generator while monitoring oil pressure manually
  3. Confirm the trip, start the standby generator, restore essential services and investigate the cause before restarting Correct answer.
  4. Reset the alarm and restart the generator immediately to restore the load

Explanation

After an automatic trip, the standby generator should be brought on load to maintain essential services, and the cause must be found before any restart attempt. Immediate restart or defeating the trip risks severe bearing damage. Adjusting the setpoint does not correct the underlying low pressure and hides a real fault.

Question 39Marine Engineering Knowledge and Machinery Operation

A ship's main engine is fitted with a shaft generator. Which operational limitation must the chief engineer respect when the shaft generator is supplying the ship's electrical load?

  1. The main engine may be manoeuvred freely because the shaft generator is isolated automatically
  2. The main engine speed must be held within the range that keeps the shaft generator frequency within limits Correct answer.
  3. The shaft generator may be operated only when the main engine is stopped
  4. The electrical load must be transferred to the auxiliary generator before any speed change

Explanation

A shaft generator's frequency is directly proportional to engine speed, so engine speed must be kept within the band that holds frequency within acceptable limits for the connected consumers. Manoeuvring requires transfer of load to the auxiliary generator because speed changes would upset frequency. The generator cannot operate with the engine stopped.

Question 40Marine Engineering Knowledge and Machinery Operation

During a crankcase inspection on a large two-stroke engine, oil mist is found on internal surfaces and the oil mist detector has recently alarmed. Which condition is the most probable cause?

  1. A hot spot from a failing bearing or worn piston rod packing overheating the oil Correct answer.
  2. A slightly low crankcase oil level at the time of the inspection
  3. Excessive ventilation of the crankcase space
  4. Normal oil splash from the running gear during the previous voyage

Explanation

Oil mist in the crankcase together with an oil mist detector alarm indicates a local hot spot, typically a failing bearing or a leaking piston rod stuffing box allowing hot gases to overheat oil. This is a serious fire and explosion risk and must be investigated before running. Normal splash, slightly low level and ventilation do not produce mist that trips the detector.

Question 41Marine Propulsion Systems and Auxiliary Machinery

During manoeuvring, a main diesel engine is switched from heavy fuel oil to marine diesel oil before stopping. What is the primary technical reason for this changeover?

  1. To raise the compression pressure inside the cylinders before the engine stops
  2. To reduce the sulphur content of the exhaust gas during the stopping sequence
  3. To increase the viscosity of the fuel so that the fuel pumps retain a better seal
  4. To remove residual heavy fuel from the injection system and avoid deposits or seizure on restart Correct answer.

Explanation

Heavy fuel oil must be flushed out of pumps, injectors and lines with distillate before the engine cools, because cooled heavy fuel becomes extremely viscous and can carbonise or block the injection equipment. This flushing also prevents the fuel from solidifying and seizing plungers and needles during standstill. It has nothing to do with compression pressure, viscosity increase or exhaust sulphur.

Question 42Marine Propulsion Systems and Auxiliary Machinery

Which component in a four-stroke marine diesel engine directly actuates the inlet and exhaust valves through pushrods and rocker arms?

  1. The fuel injection pump
  2. The turbocharger
  3. The governor
  4. The camshaft Correct answer.

Explanation

The camshaft carries cams that rotate with the crankshaft at half speed on a four-stroke engine and operate the valve gear via tappets, pushrods and rockers. The injection pump is timed by its own cam but does not open the gas-exchange valves. Turbocharger and governor have completely different functions.

Question 43Marine Propulsion Systems and Auxiliary Machinery

A ship's main engine is running steadily when the jacket cooling water outlet temperature begins to rise slowly while the seawater inlet temperature is unchanged. Which fault is the most plausible first check?

  1. A worn cylinder liner
  2. A fouled fresh-water cooler on the seawater side Correct answer.
  3. A leaking exhaust valve seat
  4. An incorrect fuel injection timing

Explanation

A gradual rise in jacket water temperature with unchanged seawater temperature typically indicates reduced heat transfer in the fresh-water cooler, such as fouling or scale on the seawater side. Valve leakage, liner wear and injection timing affect combustion and exhaust temperature rather than the overall jacket water balance in this way. Checking cooler performance is the logical first step.

Question 44Marine Propulsion Systems and Auxiliary Machinery

In a diesel engine, what does the term 'scavenging' describe?

  1. The centrifugal separation of water droplets from the fuel oil before injection
  2. The removal of burnt gases from the cylinder and their replacement with fresh charge air Correct answer.
  3. The process of purging air from the fuel injection system before starting
  4. The mechanical cleaning of the turbocharger compressor wheel during operation

Explanation

Scavenging is the gas-exchange phase in which residual burnt gases are swept out of the cylinder and replaced by fresh air, usually assisted by a scavenge receiver and ports in two-stroke engines. It is a cylinder process and should not be confused with fuel system venting or turbocharger cleaning.

Question 45Marine Propulsion Systems and Auxiliary Machinery

Which type of pump is normally used as the main seawater cooling pump on a large merchant vessel because it can handle large volumes at low head with good efficiency?

  1. A reciprocating plunger pump
  2. A screw pump
  3. A gear pump
  4. A centrifugal pump Correct answer.

Explanation

Centrifugal pumps are chosen for main seawater cooling because they deliver large flows against the relatively low head of the cooling system and are compact and reliable. Positive-displacement pumps such as plunger, gear and screw types are used where high pressure or precise metering is required.

Question 46Marine Propulsion Systems and Auxiliary Machinery

What is the purpose of the air receiver in a starting-air system for a main diesel engine?

  1. To cool the compressed air after the last stage of the compressor
  2. To store compressed air at working pressure for engine starting and for control air consumers Correct answer.
  3. To regulate the fuel rack position during starting
  4. To separate water and oil from the compressed air before it enters the cylinders

Explanation

The air receiver is a pressure vessel that stores compressed air so that sufficient quantity and pressure are available for starting the engine and for pneumatic controls. Draining condensate is a maintenance action, but separation is not the receiver's main purpose. Cooling is done by intercoolers and aftercoolers, and fuel rack control is mechanical or hydraulic.

Question 47Marine Propulsion Systems and Auxiliary Machinery

A marine auxiliary boiler shows a low water level alarm. What is the correct immediate automatic action expected from the boiler safety system?

  1. Open the main steam stop valve fully
  2. Start the feed pump at maximum capacity without any other action
  3. Increase the fuel supply to restore steam output
  4. Trip the burner and cut off fuel to the boiler Correct answer.

Explanation

On a low water level alarm the burner management system must cut off fuel to prevent overheating and possible explosion of the boiler. Restoring feed water is then carried out under controlled conditions, but the immediate protective action is to stop firing. Increasing fuel or steam demand would worsen the unsafe condition.

Question 48Marine Propulsion Systems and Auxiliary Machinery

Which of the following best describes the function of a marine engine's governor?

  1. It maintains the engine speed by adjusting fuel delivery in response to load changes Correct answer.
  2. It limits the maximum cylinder pressure by opening a relief valve
  3. It maintains the lubricating oil pressure by adjusting the pump stroke
  4. It controls the cooling water temperature by modulating the seawater valve

Explanation

The governor senses engine speed and adjusts the fuel rack or fuel quantity to hold the set speed as load varies. It is a speed-control device and does not regulate lube oil pressure, cooling water temperature or cylinder relief valves. Those functions belong to separate control loops and safety devices.

Question 49Marine Propulsion Systems and Auxiliary Machinery

A two-stroke crosshead main engine shows a rising piston underside (crankcase) pressure on one unit and oil mist is detected in the crankcase. What is the most appropriate immediate action?

  1. Open the crankcase doors to ventilate the space
  2. Increase cylinder lubricating oil feed to the affected unit
  3. Stop the engine immediately and investigate the affected unit Correct answer.
  4. Reduce load gradually and continue to the next port

Explanation

Oil mist in the crankcase together with abnormal crankcase pressure is a serious explosion risk, and the engine must be stopped at once. Opening crankcase doors while the engine is hot and running is extremely dangerous, and continuing under reduced load does not remove the ignition source. Increasing cylinder lubrication does not address the fault.

Question 50Marine Propulsion Systems and Auxiliary Machinery

In a turbocharged diesel engine, what is the effect of fouling on the compressor side of the turbocharger?

  1. Turbine speed falls to zero while the engine continues at full load
  2. Cylinder lubricating oil consumption decreases sharply
  3. Compressor efficiency falls, scavenge air pressure drops and exhaust gas temperature rises Correct answer.
  4. Compressor efficiency rises and scavenge air pressure increases

Explanation

Fouling on the compressor reduces its efficiency and the pressure ratio, so scavenge air pressure falls and exhaust gas temperature rises for a given load. The turbocharger does not stop rotating, and cylinder oil consumption is not directly reduced by compressor fouling. Performance monitoring and water washing are used to detect and correct this.