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KMA Cadet 1st-Stage Exam study materials
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KMA Cadet 1st-Stage Exam practice questions

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Question 1Nautical Science and Navigation

On a nautical chart, the latitude scale on the left and right edges is used to measure distance because one minute of latitude equals which distance?

  1. One cable
  2. One nautical mile Correct answer.
  3. One kilometre
  4. One statute mile

Explanation

The nautical mile is defined so that one minute of arc of latitude corresponds to one nautical mile, approximately 1852 metres. This is why dividers are set against the vertical latitude scale rather than the horizontal longitude scale when measuring distance on a chart.

Question 2Nautical Science and Navigation

A vessel steering 000° true with a westerly variation of 6° applies which compass course, assuming deviation is zero?

  1. 006° compass Correct answer.
  2. 354° compass
  3. 000° compass
  4. 186° compass

Explanation

Variation west is applied by adding it when converting from true to compass course: true 000° plus 6° west gives 006° compass. The mnemonic is that westerly errors are added when going from true to compass.

Question 3Nautical Science and Navigation

In the IALA Maritime Buoyage System Region A, a conical buoy painted red is normally which kind of mark?

  1. Special mark
  2. Starboard-hand mark
  3. Port-hand mark Correct answer.
  4. Safe water mark

Explanation

In Region A, port-hand marks are red and can-shaped, while starboard-hand marks are green and conical. A conical red buoy therefore does not fit the standard port-hand shape and should be treated with caution as an unusual configuration.

Question 4Nautical Science and Navigation

A vessel's log records a distance run of 12.5 nautical miles in 50 minutes. What is the average speed over the ground in knots?

  1. 12.5 knots
  2. 15.0 knots Correct answer.
  3. 10.0 knots
  4. 25.0 knots

Explanation

Speed in knots equals distance in nautical miles divided by time in hours. Fifty minutes is 0.8333 hours, and 12.5 divided by 0.8333 gives 15.0 knots.

Question 5Nautical Science and Navigation

Which term describes the vertical distance from the waterline to the lowest point of a vessel's keel?

  1. Beam
  2. Draught Correct answer.
  3. Freeboard
  4. Air draught

Explanation

Draught is the vertical measurement from the waterline down to the lowest part of the hull or keel. It determines the minimum depth of water needed for safe navigation and is read from draught marks near the bow and stern.

Question 6Nautical Science and Navigation

On a Mercator chart, what happens to the spacing of the latitude parallels as latitude increases?

  1. The spacing decreases toward the poles
  2. The spacing increases toward the poles Correct answer.
  3. The spacing becomes equal to the longitude spacing at the equator
  4. The spacing remains constant everywhere

Explanation

The Mercator projection stretches the latitude scale progressively toward the poles so that rhumb lines plot as straight lines. This is why a single scale cannot be used across a long ocean passage and distance must be measured at the latitude of the vessel.

Question 7Nautical Science and Navigation

What is the primary purpose of a vessel's echo sounder?

  1. To determine the vessel's heading
  2. To measure the vessel's speed through the water
  3. To detect other vessels at long range
  4. To measure the depth of water beneath the keel Correct answer.

Explanation

An echo sounder transmits an acoustic pulse downward and times its return from the seabed to display depth under the transducer. This reading supports safe navigation and is often compared with charted depths and the vessel's draught.

Question 8Nautical Science and Navigation

Which statement correctly describes the relationship between true north and magnetic north?

  1. Magnetic north is fixed while true north moves
  2. The angle between them at a given place is the magnetic variation Correct answer.
  3. They are always identical at sea
  4. The angle between them is called deviation

Explanation

Variation is the angular difference between true north and magnetic north at a particular position and date, and it changes slowly as the magnetic pole drifts. Deviation, by contrast, is the error caused by the vessel's own magnetic field.

Question 9Nautical Science and Navigation

A vessel travels due east for 60 nautical miles along the equator. What is the approximate change in longitude?

  1. 6° of longitude
  2. 0.5° of longitude
  3. 1° of longitude Correct answer.
  4. 60° of longitude

Explanation

At the equator one minute of longitude equals one nautical mile, so 60 nautical miles corresponds to 60 minutes of arc, which is 1°. The relationship does not hold away from the equator because the meridians converge.

Question 10Nautical Science and Navigation

A vessel steams 090° true for 20 nautical miles, then 000° true for 15 nautical miles. What is the approximate final position relative to the start?

  1. 15 miles east and 20 miles north
  2. 5 miles east and 5 miles north
  3. 20 miles east and 15 miles north Correct answer.
  4. 35 miles northeast

Explanation

The first leg produces a departure of 20 miles to the east with no change in latitude. The second leg produces 15 miles of northing with no change in departure, so the net displacement is 20 miles east and 15 miles north.

Question 11Nautical Science and Navigation

Under the International Regulations for Preventing Collisions at Sea, two power-driven vessels meeting on reciprocal or nearly reciprocal courses risk a head-on situation. What action is required?

  1. Both vessels alter course to port and pass starboard to starboard
  2. Both vessels alter course to starboard and pass port to port Correct answer.
  3. Both vessels maintain course and speed
  4. The vessel with the other on its starboard side gives way

Explanation

In a head-on situation each vessel must alter course to starboard so that they pass port to port, and each should sound one short blast. Neither vessel is the give-way vessel in this situation; both share the obligation.

Question 12Nautical Science and Navigation

A vessel observes another vessel bearing steady and the range decreasing over time. What does this indicate?

  1. The other vessel is overtaking
  2. The other vessel is at anchor
  3. No risk of collision exists
  4. A risk of collision exists Correct answer.

Explanation

A constant bearing with decreasing range is the classic indication that the two vessels are converging on a collision course. The bearing should be monitored repeatedly because a slowly changing bearing at long range can still hide a developing risk.

Question 13Nautical Science and Navigation

The charted depth in a channel is 7.4 metres at chart datum. If the height of tide is 2.1 metres and the vessel's draught is 5.0 metres, what is the approximate under-keel clearance?

  1. 2.4 metres
  2. 4.5 metres Correct answer.
  3. 0.3 metres
  4. 7.1 metres

Explanation

Actual depth of water equals charted depth plus height of tide, giving 9.5 metres. Subtracting the draught of 5.0 metres leaves an under-keel clearance of 4.5 metres.

Question 14Nautical Science and Navigation

What is the essential difference between a rhumb line and a great circle on the Earth's surface?

  1. A rhumb line crosses every meridian at the same angle, while a great circle is the shortest path Correct answer.
  2. A rhumb line is always the shortest path between two points
  3. A great circle cannot be plotted on a Mercator chart
  4. A rhumb line only exists in the northern hemisphere

Explanation

A rhumb line maintains a constant bearing relative to all meridians, which makes it easy to steer but not the shortest distance. A great circle is the intersection of the surface with a plane through the Earth's centre and gives the shortest track.

Question 15Nautical Science and Navigation

A sextant reading of the sun's lower limb gives a sextant altitude of 32° 14.6'. The index error is 2.0' off the arc. What is the corrected sextant altitude?

  1. 32° 16.6' Correct answer.
  2. 32° 18.6'
  3. 32° 12.6'
  4. 32° 14.6'

Explanation

An index error off the arc is added to the sextant altitude, while an error on the arc is subtracted. Adding 2.0' to 32° 14.6' gives 32° 16.6' before applying dip and other corrections.

Question 16Nautical Science and Navigation

Which of the following is the correct order of operations when plotting a running fix?

  1. Plot both bearings from the same position and bisect the angle
  2. Plot the second bearing first and transfer it backward along the track
  3. Plot the first bearing, advance the position along the course and distance run, then cross with the second bearing Correct answer.
  4. Average the two bearings and plot a single line of position

Explanation

A running fix uses one line of position advanced by the vessel's course and distance run to the time of a later observation. The advanced line is then crossed with the second line of position to give the fix.

Question 17Nautical Science and Navigation

A tropical revolving storm in the northern hemisphere has its centre bearing due south of the vessel. In which direction should the vessel proceed to move away from the storm track most safely?

  1. Toward the west, across the advancing semicircle
  2. Toward the north, directly into the storm centre
  3. Toward the east, keeping the wind on the starboard quarter Correct answer.
  4. Hold course and reduce speed to ride out the storm

Explanation

In the northern hemisphere the dangerous semicircle lies to the right of the storm track, and a vessel south of the centre should steer to put the wind on the starboard quarter to move away. Heading east in this geometry increases the distance from the advancing centre.

Question 18Nautical Science and Navigation

What does a charted symbol showing a sounding in fathoms and feet, such as 5 with a subscript 2, represent?

  1. 5 feet and 2 inches
  2. 5 metres and 2 decimetres
  3. 5 fathoms and 2 feet Correct answer.
  4. 5 cables and 2 fathoms

Explanation

Older charts and some modern ones use a mixed notation in which the large figure is fathoms and the small subscript is feet. The total depth is therefore 5 fathoms 2 feet, or about 10.3 metres.

Question 19Nautical Science and Navigation

A vessel's gyrocompass has a known error of 3° east. If the gyro bearing of a lighthouse is 045°, what is the true bearing?

  1. 048°
  2. 045°
  3. 315°
  4. 042° Correct answer.

Explanation

A gyro error east means the compass reads higher than the true bearing, so the error is subtracted to obtain the true bearing. Subtracting 3° from 045° gives 042° true.

Question 20Nautical Science and Navigation

Which publication provides the standard list of charted symbols, abbreviations and terms used on nautical charts?

  1. Chart 5011 Correct answer.
  2. The Mariners' Handbook
  3. The Nautical Almanac
  4. The International Code of Signals

Explanation

Chart 5011, published by the International Hydrographic Organization, is the reference for symbols, abbreviations and terms used on charts. It is used alongside the chart catalogue and national chart publications.

Question 21Nautical Science and Navigation

A vessel is in a crossing situation with another power-driven vessel on its starboard side. Which vessel is the stand-on vessel?

  1. The faster vessel
  2. The vessel nearer to the channel edge
  3. The vessel that has the other on its port side Correct answer.
  4. The vessel that has the other on its starboard side

Explanation

In a crossing situation between two power-driven vessels the vessel with the other on its starboard side must give way. The other vessel, which has the give-way vessel on its port side, is the stand-on vessel and must keep her course and speed.

Question 22Nautical Science and Navigation

In the IALA Region A system, what does a cardinal mark with two cones both pointing upward indicate?

  1. The mark indicates a special area
  2. The mark is a safe water mark
  3. The safest water lies to the south of the mark
  4. The safest water lies to the north of the mark Correct answer.

Explanation

A north cardinal mark carries two cones both pointing upward and indicates that navigable water lies to the north of the mark. Its topmark and black-over-yellow colour pattern reinforce the same meaning.

Question 23Nautical Science and Navigation

A vessel's position is fixed by two simultaneous bearings, but the lines of position cross at a very small angle. What is the main weakness of this fix?

  1. Small errors in either bearing cause a large positional error Correct answer.
  2. The fix cannot be plotted on a Mercator chart
  3. The fix is invalid unless three bearings are used
  4. The bearings must be taken from the same object

Explanation

When lines of position intersect at a small angle, the resulting position is poorly defined because a slight bearing error shifts the intersection a long way. A wider crossing angle, ideally near 90°, gives a much more reliable fix.

Question 24Nautical Science and Navigation

A vessel steams 000° true at 12 knots for 2 hours, then 090° true at 12 knots for 2 hours. What is the approximate course made good from the starting position?

  1. 135°
  2. 000°
  3. 090°
  4. 045° Correct answer.

Explanation

The two legs produce equal northings and eastings of 24 nautical miles each. Equal components in the north and east directions give a course made good of 045° true.

Question 25Nautical Science and Navigation

A vessel's chronometer reads 10:00:00 UTC when a time signal indicates 10:00:12 UTC. The chronometer error is 12 seconds slow. The vessel then takes a sight at chronometer time 14:30:00. What is the correct UTC of the sight?

  1. 14:30:12 Correct answer.
  2. 14:30:00
  3. 14:42:00
  4. 14:29:48

Explanation

A chronometer that is slow means the true time is later than the reading by the stated error. Adding 12 seconds to 14:30:00 gives 14:30:12 UTC for the sight.

Question 26Nautical Science and Navigation

A vessel's log records a distance run of 128 nautical miles in 8 hours. What is the average speed made good in knots?

  1. 12 knots
  2. 16 knots Correct answer.
  3. 18 knots
  4. 14 knots

Explanation

Speed in knots is distance in nautical miles divided by time in hours, because one knot equals one nautical mile per hour. Dividing 128 by 8 gives 16 knots, which is the speed made good over the ground for that run.

Question 27Nautical Science and Navigation

Which statement correctly describes the meaning of chart datum on a nautical chart?

  1. The average level of high water used for clearing heights under bridges
  2. The vessel's loaded waterline used to compute under-keel clearance
  3. The standard level of the sea used for all meteorological pressure reports
  4. The level to which charted depths are referred, normally approximately the lowest astronomical tide Correct answer.

Explanation

Charted soundings are measured downward from chart datum, which is chosen so that the water is rarely lower than the charted depth. In most areas this is approximately the lowest astronomical tide, so predicted tide height added to charted depth gives the actual depth.

Question 28Nautical Science and Navigation

A vessel steering 090° true observes a light bearing 045° true. What is the bearing of the light relative to the vessel's head, expressed as a relative bearing?

  1. 135° relative
  2. 045° relative
  3. 315° relative Correct answer.
  4. 090° relative

Explanation

Relative bearing is found by subtracting the vessel's heading from the true bearing of the object. Here 045° minus 090° gives minus 45°, which is expressed as 315° relative, meaning the light is on the port bow.

Question 29Nautical Science and Navigation

What is the primary function of a vessel's magnetic compass?

  1. To measure the vessel's speed through the water by electromagnetic induction
  2. To determine the vessel's position by receiving satellite signals
  3. To provide a gyroscopically stabilised heading with no deviation
  4. To indicate direction by reference to the Earth's magnetic field, independently of any power supply Correct answer.

Explanation

The magnetic compass aligns itself with the horizontal component of the Earth's magnetic field and therefore needs no electrical power. Its indicated heading must be corrected for variation and for the vessel's own deviation before it can be used as a true heading.

Question 30Nautical Science and Navigation

A vessel's echo sounder indicates a depth of 20 metres below the transducer, and the transducer is mounted 3 metres below the waterline. What is the depth of water below the keel when the vessel's draught is 5 metres?

  1. 23 metres
  2. 15 metres
  3. 18 metres Correct answer.
  4. 12 metres

Explanation

The sounder measures from the transducer, so the total depth below the waterline is 20 plus 3 metres, or 23 metres. Subtracting the draught of 5 metres gives 18 metres of water beneath the keel.

Question 31Nautical Science and Navigation

A vessel is required to determine compass deviation. Which statement correctly describes deviation?

  1. It is the angular difference between true north and magnetic north at the vessel's position
  2. It is the angular difference between the magnetic heading and the compass heading, caused by the vessel's own magnetism Correct answer.
  3. It is the change in compass error observed when the vessel alters course through 180°
  4. It is the constant error caused by misalignment of the compass bowl with the keel

Explanation

Deviation arises from magnetic fields generated by the vessel's structure and equipment acting on the compass needle. It varies with the vessel's heading and must be obtained from a deviation table or by comparison with a known reference such as a gyrocompass.

Question 32Nautical Science and Navigation

In the IALA Region A buoyage system, what does a preferred channel mark with red over green horizontal bands indicate?

  1. The mark is a safe-water mark indicating deep water all around
  2. The preferred channel lies to starboard of the mark when proceeding in the direction of buoyage Correct answer.
  3. The preferred channel lies to port of the mark when proceeding in the direction of buoyage
  4. The mark indicates a special area such as a spoil ground

Explanation

A preferred channel mark carries the colour of the lateral mark for the preferred side at the top. In Region A, red at the top means the preferred channel passes to starboard of the mark when following the direction of buoyage.

Question 33Nautical Science and Navigation

A vessel's position is fixed by a single position line from a bearing and a sounding taken at the same time. Which statement best describes the resulting position?

  1. It is unreliable because a sounding cannot be plotted on a chart
  2. It is a precise fix because two independent observations were used
  3. It is a dead reckoning position with no observational correction
  4. It is a running fix and its accuracy depends mainly on the course and speed made good between observations Correct answer.

Explanation

A bearing and a sounding taken simultaneously give a position line and a depth contour, but the sounding only confirms position along that line. When observations are separated in time, the earlier line must be advanced by the course and speed made good, making it a running fix whose accuracy depends on that transfer.

Question 34Nautical Science and Navigation

A vessel's sextant has an index error of 2.5' off the arc. The observed sextant altitude of a star is 40° 10.0'. What is the corrected altitude before any other corrections are applied?

  1. 40° 12.5' Correct answer.
  2. 40° 05.0'
  3. 40° 15.0'
  4. 40° 07.5'

Explanation

An index error off the arc means the sextant reads less than the true angle, so the error is added to the observed altitude. Adding 2.5 minutes to 40° 10.0' gives a corrected altitude of 40° 12.5'.

Question 35Nautical Science and Navigation

A vessel observes a light at a distance greater than the sum of the geographic and luminous ranges shown on the chart. What is the most likely explanation?

  1. The observer has confused true and magnetic bearings
  2. The charted ranges are always understated and can be exceeded routinely
  3. The light is being seen by abnormal refraction or a mirage, so the observation should be treated with caution Correct answer.
  4. The light has been reclassified as a major landfall light without chart amendment

Explanation

The charted ranges assume standard atmospheric conditions and normal observer height. Seeing a light well beyond the calculated range indicates abnormal refraction, which can also distort bearings, so such observations should not be relied upon for position fixing.

Question 36Nautical Science and Navigation

Which statement correctly explains why a great circle track appears as a curved line on a Mercator chart?

  1. The Mercator projection shows great circles as curves because it is not conformal
  2. The Mercator projection is conformal and expands latitude scale with latitude, so great circles plot as curves concave to the equator Correct answer.
  3. The Mercator projection distorts distance uniformly, so all great circles plot as straight lines
  4. The Mercator projection is a perspective projection from the centre of the Earth, producing curved parallels

Explanation

On a Mercator chart the latitude scale increases with latitude so that rhumb lines plot as straight lines and angles are preserved. A great circle crosses meridians at changing angles, so it plots as a curve bending toward the equator.

Question 37Nautical Science and Navigation

A vessel is proceeding in a narrow channel. In accordance with the Collision Regulations, which action is required of a vessel of less than 20 metres in length or a sailing vessel?

  1. It must anchor until the channel is clear of larger vessels
  2. It must keep to the starboard edge of the channel regardless of depth
  3. It shall not impede the passage of a vessel that can safely navigate only within the narrow channel Correct answer.
  4. It has absolute right of way over all other vessels in the channel

Explanation

Rule 9 requires small vessels and sailing vessels to avoid impeding a vessel that can safely navigate only within the narrow channel or fairway. This does not remove the obligation of the larger vessel to navigate with caution.

Question 38Nautical Science and Navigation

A vessel at anchor in a strong tidal stream lies to her anchor with the cable leading ahead. She then swings through 180° as the tide turns. Which statement best describes the resulting risk to the anchor?

  1. The vessel will drag because the holding ground is unchanged
  2. The anchor will always break out of the seabed and drag immediately
  3. The cable may foul the anchor stock or flukes, so the anchor should be weighed and re-laid if the vessel does not swing cleanly Correct answer.
  4. The cable will part because the load reverses direction

Explanation

When the tide turns, the vessel swings around the anchor and the cable can take a turn around the stock or flukes, preventing a clean lead. If the vessel does not swing cleanly, the anchor should be weighed and re-laid to avoid fouling and dragging.

Question 39Nautical Science and Navigation

A vessel's gyrocompass is settled and running, but its repeaters show a heading that differs by a constant 4° from the master compass. What is the most appropriate interpretation?

  1. The gyrocompass has excessive latitude error and must be switched off
  2. The vessel's deviation has changed by 4°
  3. The master compass has failed and the repeaters are correct
  4. A repeater alignment error exists, and the repeaters should be synchronised to the master compass before use Correct answer.

Explanation

A constant offset between the master gyrocompass and its repeaters indicates a misalignment in the repeater transmission system rather than a compass error. The repeaters should be synchronised to the master, and the master's own error checked separately.

Question 40Nautical Science and Navigation

A vessel is navigating in fog and hears a fog signal of one prolonged blast followed by two short blasts from a vessel whose position is not yet determined. What does this signal indicate, and what should the vessel do?

  1. It indicates a vessel aground, so the vessel should alter course away from the channel
  2. It indicates a vessel not under command, constrained by draught, or engaged in fishing, and the vessel should reduce speed to the minimum and be ready to stop Correct answer.
  3. It indicates a vessel at anchor, so the vessel should pass ahead of it
  4. It indicates a vessel underway and making way, so the vessel should maintain course and speed

Explanation

Under the Collision Regulations this signal is made by a vessel not under command, restricted in her ability to manoeuvre, constrained by draught, sailing, or engaged in fishing. On hearing it in fog, the vessel should proceed at a safe speed and be prepared to stop.

Question 41Marine Engineering and Ship Propulsion Systems

In a four-stroke diesel engine, which stroke immediately follows the compression stroke in the operating cycle?

  1. Exhaust stroke
  2. Scavenging stroke
  3. Power (expansion) stroke Correct answer.
  4. Intake (suction) stroke

Explanation

In the four-stroke cycle the order is intake, compression, power, then exhaust. Compression raises charge temperature so that combustion drives the piston down on the power stroke. Scavenging is a two-stroke term, not a separate fourth stroke.

Question 42Marine Engineering and Ship Propulsion Systems

What is the primary function of a ship's propeller shaft bearing located in the stern tube?

  1. To increase shaft rotational speed
  2. To filter seawater before it reaches the engine
  3. To support the shaft and carry propeller thrust loads Correct answer.
  4. To cool the main engine cylinder liners

Explanation

Stern tube bearings support the tail shaft and absorb the radial loads of the propeller while allowing rotation. Lubrication may be oil or seawater dependent, but the bearing's structural duty is load support. It does not change speed or serve engine cooling.

Question 43Marine Engineering and Ship Propulsion Systems

A vessel's main engine is rated at 6,000 kW and drives a propeller at 120 rpm. Using the relationship power equals torque times angular velocity, what approximate shaft torque is being transmitted?

  1. Approximately 50 kN·m
  2. Approximately 4,770 kN·m
  3. Approximately 7,640 kN·m
  4. Approximately 477 kN·m Correct answer.

Explanation

Angular velocity is 2π × (120/60) = 12.57 rad/s. Torque equals power divided by angular velocity, so 6,000,000 W ÷ 12.57 rad/s ≈ 477 kN·m. This confirms the order of magnitude expected for large slow-speed shafting.

Question 44Marine Engineering and Ship Propulsion Systems

Why is a controllable-pitch propeller advantageous for a vessel required to manoeuvre frequently in port?

  1. It eliminates the need for any reduction gearing
  2. Propeller blade angle can be changed to give reverse thrust without reversing the engine Correct answer.
  3. It removes the requirement for a rudder
  4. It allows the engine to run at constant load regardless of pitch setting

Explanation

With a controllable-pitch propeller, blade angle is altered hydraulically so thrust direction and magnitude change while shaft rotation continues in one direction. This avoids repeated stopping and reversing of a large engine during manoeuvres. Gearing and rudder requirements remain.

Question 45Marine Engineering and Ship Propulsion Systems

In a marine fuel oil system, what is the purpose of the settling tank ahead of the service tank?

  1. To meter fuel flow to each cylinder
  2. To raise fuel viscosity to injection levels
  3. To remove dissolved sulphur from the fuel
  4. To allow heavy solids and water to separate by gravity before fuel is transferred Correct answer.

Explanation

Settling tanks give heavy fuel oil residence time so that water and coarse solids drop to the bottom for draining. This reduces loading on purifiers and filters downstream. Viscosity control and metering occur elsewhere in the system, and sulphur cannot be removed by settling.

Question 46Marine Engineering and Ship Propulsion Systems

A centrifugal purifier is used on heavy fuel oil. Which adjustment most directly controls whether the unit separates water or solid impurities?

  1. The position of the gravity disc in the outlet bowl Correct answer.
  2. The setting of the fuel injection timing
  3. The temperature of the fuel service tank
  4. The speed of the fuel transfer pump

Explanation

The gravity disc sets the position of the oil-water interface inside the bowl. Choosing the correct disc for the fuel density allows either water removal or solids removal to be optimised. Pump speed, tank temperature and injection timing do not set the interface.

Question 47Marine Engineering and Ship Propulsion Systems

What is the main reason jacket cooling water for a marine diesel engine is pressurised and treated with corrosion inhibitors?

  1. To raise the boiling point and protect liners from corrosion and cavitation Correct answer.
  2. To reduce the engine's compression ratio
  3. To lubricate the turbocharger bearings
  4. To increase the fuel's cetane number

Explanation

Pressurising the cooling circuit raises the boiling point and suppresses cavitation at liner surfaces, while inhibitor chemicals protect against corrosion and erosion. The coolant does not affect fuel quality, turbocharger bearing lubrication, or compression ratio.

Question 48Marine Engineering and Ship Propulsion Systems

During a routine watch, the main engine exhaust gas temperature at one unit rises sharply while all other units remain normal. Which action is most appropriate first?

  1. Reduce load on that unit and investigate fuel injection and exhaust valve condition Correct answer.
  2. Add more cylinder oil to that unit
  3. Ignore the reading until the next port call
  4. Increase the load to burn off carbon deposits

Explanation

A single-unit exhaust temperature excursion usually indicates a fuel injector fault, valve leakage, or scavenge problem. Reducing load limits thermal stress while the cause is investigated. Increasing load or ignoring the alarm risks damage, and extra cylinder oil does not address combustion faults.

Question 49Marine Engineering and Ship Propulsion Systems

Which statement correctly describes the role of the scavenge air receiver in a large two-stroke diesel engine?

  1. It stores fuel oil under pressure for injection
  2. It acts as a reservoir for lubricating oil
  3. It houses the camshaft for exhaust valve actuation
  4. It stores pressurised air from the turbocharger for cylinder charging and uniflow scavenging Correct answer.

Explanation

In a uniflow-scavenged two-stroke engine, the scavenge air receiver holds air delivered by the turbocharger or blower. This air enters through scavenge ports to sweep out exhaust gases and supply combustion air. It is not a fuel, camshaft, or lube oil component.

Question 50Marine Engineering and Ship Propulsion Systems

A ship's turbocharger is surging repeatedly at high load. Which condition is the most likely contributing cause?

  1. Excessive back pressure in the exhaust system or fouled turbine and air cooler Correct answer.
  2. Too little lubricating oil in the main engine sump
  3. Low fuel oil viscosity at the injectors
  4. Incorrect propeller pitch setting at the bridge

Explanation

Turbocharger surge occurs when compressor delivery pressure cannot overcome downstream resistance or when turbine performance is degraded. High exhaust back pressure or fouled turbine nozzles and air coolers are classic causes. Sump oil level, bridge pitch settings, and injector viscosity do not directly cause surge.