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Motor Plants and Auxiliary Boilers - USCG Exam Questions

Diesel engine theory and operation, fuel and lubrication systems, starting and reversing, and auxiliary boilers.

Every question below is a real U.S. Coast Guard exam question with four choices. Answer one and the correct choice is revealed instantly, with the USCG reference and illustration where the question uses one.

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All Motor Plants and Auxiliary Boilers questions

Questions 301–400 of 1,433 · page 4 of 15

  1. #456 With respect to diesel fuel, the ease with which a cold engine will start is dependent upon the __________.
  2. #457 The ignition quality of diesel fuel becomes LESS critical as __________.
  3. #458 The cetane number rates fuels for diesel engines according to its __________.
  4. #459 Which of the following statements is true concerning the cetane number of diesel fuel?
  5. #460 A mixture of 45% cetane and 55% alpha-methyl-naphthalene is found to have the same ignition delay as a sample of diesel oil. The sample can be describ...
  6. #462 For optimum results, centrifugal purification of heavy fuel oil should be accomplished with the fuel at the lowest practicable __________.
  7. #463 Which of the listed substances can be satisfactorily removed from diesel fuel by centrifuging?
  8. #464 Whether using a centrifuge or a simple filter, oil cleaning and filtration will be the most effective when the oil is at a __________.
  9. #465 The temperature of the contaminated fuel oil fed to the centrifuge shown in the illustration should be __________. Illustration MO-0012 illustration
  10. #466 The device shown in the illustration can be automatically or manually desludged. The closing sequence at the end of the desludging cycle is initiated... illustration
  11. #467 The greatest difference between the centrifuge bowl shown in the illustration and that of a tubular bowl, with straight, vertical, interior surfaces,... illustration
  12. #471 Which of the following statements is accurate concerning the vibration sensing device used with the separator shown in the illustration? Illustration... illustration
  13. #474 All alarms occurring on the control unit of the device shown in the illustration will __________. Illustration MO-0127 illustration
  14. #475 How may water be removed from the bowl of the separator as shown in the illustration? Illustration MO-0127 illustration
  15. #476 Which of the following statements represents the working principle of the water transducer used with the separator shown in the illustration? Illustra... illustration
  16. #477 The device labeled "A", shown in the illustration, is known as the __________. Illustration MO-0112 illustration
  17. #478 The device labeled 'C' shown in the illustration is known as the __________. Illustration MO-0112 illustration
  18. #479 The device labeled "B", shown in the illustration is known as the __________. Illustration MO-0112 illustration
  19. #480 The device labeled "D", as shown in the illustration, is the bowl __________. Illustration MO-0112 illustration
  20. #481 The item indicated by the letter "F" of the device shown in the illustration is the __________. Illustration MO-0112 illustration
  21. #482 The device labeled "H", shown in the illustration is referred to as the __________. Illustration MO-0112 illustration
  22. #483 The force developed by the liquid within space "J" of the device shown in the illustration depends upon __________. Illustration MO-0112 illustration
  23. #484 During normal operation, the liquid retained in space 'J' of the device shown in the illustration is __________. Illustration MO-0112 illustration
  24. #485 The area indicated by the letter "L" of the device shown in the illustration is properly called the __________. Illustration MO-0112 illustration
  25. #486 Which of the following statements describes "N" shown in the illustration? Illustration MO-0112 illustration
  26. #487 Item "O" of the device shown in the illustration is the __________. Illustration MO-0112 illustration
  27. #488 The wear liner shown in the illustration is indicated by the letter __________. Illustration MO-0112 illustration
  28. #489 The discharge nozzle shown in the illustration, is indicated by the letter __________. Illustration MO-0112 illustration
  29. #490 The gasket "U" shown in the illustration, is used to seal the liquid space below the __________. Illustration MO-0112 illustration
  30. #491 The port "X" shown in the illustration allows water to enter the adjoining chamber. During what cycle of operation will this occur? Illustration MO-01... illustration
  31. #492 The area indicated by the letter "W", shown in the illustration is correctly termed the __________. Illustration MO-0112 illustration
  32. #493 What is used as the primary operating medium during the sludge discharge cycle, shown in the illustration? Illustration MO-0112 illustration
  33. #494 Where does the shoot cycle operating liquid first come in contact with the rotating forces of the device shown in the illustration? Illustration MO-01... illustration
  34. #495 The unit shown in the illustration is beginning the sludge discharge cycle. The operating liquid solenoid valve has been energized and space "J" is fi... illustration
  35. #496 What terminates the sludge discharge cycle of the device shown in the illustration? Illustration MO-0112 illustration
  36. #497 During the normal operation of the centrifuge shown in the illustration, the operating liquid solenoid and bypass valves for the cleaning cycle should... illustration
  37. #498 If the separating temperature is to remain constant, what is the relationship between the specific gravity of the oil and the required size of the reg... illustration
  38. #504 The diesel engine shown in the illustration has the highest fuel pressure developed in the part labeled __________. Illustration MO-0003 illustration
  39. #506 For a continuous operation diesel engine, a duplex filter unit would be the best arrangement because __________.
  40. #507 As shown in the illustration, the viscosimeter would be used to directly control the output of which of the following components? Illustration MO-0077 illustration
  41. #510 Cooling the intake air supplied to a diesel engine will __________.
  42. #511 A large, low-speed, main propulsion diesel engine uses sea water to directly cool the __________.
  43. #512 An increase in the air inlet manifold pressure of a diesel engine will result in a/an __________.
  44. #513 In a naturally aspirated diesel engine, the volume of air intake is directly associated with engine __________.
  45. #515 Item labeled 'R' as shown in section 6 of the illustration is identified as the __________. Illustration MO-0025 illustration
  46. #516 Which of the air intake systems listed will result in the lowest specific fuel consumption?
  47. #517 Compared to a naturally aspirated diesel engine, a supercharged diesel engine has __________.
  48. #518 A naturally aspirated diesel engine at full throttle will have an intake manifold pressure __________.
  49. #519 The power consumed during the scavenging process of a diesel engine is known as the __________.
  50. #520 The exhaust system for a turbocharged diesel engine functions to __________.
  51. #521 Exhaust pipes for separate main propulsion diesel engines can be combined only when __________.
  52. #522 One of the factors limiting the amount of load which can be put on a modern marine diesel engine is the __________.
  53. #523 In a diesel engine exhaust system, the cooling of the exhaust gases below their dew point, will result in __________.
  54. #524 The most common instrument used to measure diesel engine exhaust pressure is the __________.
  55. #525 Which of the diesel engine exhaust mufflers listed is usually equipped with a spark arrestor?
  56. #526 A water jacket is placed around the exhaust manifolds of propulsion diesel engines to __________.
  57. #537 In the engine shown in the illustration, the part labeled 'W' is cooled by __________. Illustration MO-0003 illustration
  58. #538 The diesel engine shown in the illustration, which of the lettered parts listed is cooled by sea water? Illustration MO-0003 illustration
  59. #539 The large, slow-speed, main propulsion diesel engine shown in the illustration, the part labeled 'B' contains __________. Illustration MO-0003 illustration
  60. #544 Fuel injectors used in heavy fuel oil systems are usually provided with cooling to reduce __________.
  61. #549 What occurs within the tubes of the device labeled "23" shown in the illustration? Illustration MO-0111 illustration
  62. #560 Item "10" shown in the illustration is used to __________. Illustration MO-0111 illustration
  63. #562 The expansion tank for a diesel engine closed cooling system is designed to maintain a constant head on the system and __________.
  64. #563 The temperature at which an adjustable bellows type thermostatic valve operates is determined by __________.
  65. #564 The thermostatic valve in the illustration is used for controlling the coolant temperature in a main propulsion diesel engine. Which of the following... illustration
  66. #569 Why will a turbocharged diesel engine produce black smoke if excessive additional load is applied too quickly?
  67. #571 In a turbocharger, inlet air velocity is increased in the __________.
  68. #572 Regarding the turbocharger shown in the illustration, the part labeled "B" would be attached to the __________. Illustration MO-0080 illustration
  69. #577 In a Roots-type rotary blower, the volume of air delivered is directly proportional to __________.
  70. #578 Which of the designs listed will keep the lobes from making contact in a Roots-type blower?
  71. #581 The power consumed during the scavenging process of a diesel engine is known as the __________.
  72. #584 A loop or cross scavenged engine utilizes the motion of its pistons and a turbocharger to provide scavenging air. Which of the listed mechanical desig...
  73. #585 The device used to limit engine torque at various engine speeds is called a __________.
  74. #586 Sensitivity for a diesel engine governor is described as the __________.
  75. #587 The principal characteristic of an isochronous governor is it will __________.
  76. #588 Diesel engine control can be obtained by the bridge __________.
  77. #589 Diesel engines driving alternators operating in parallel must maintain a set frequency regardless of load changes. The governor characteristic used to...
  78. #590 Direct reversible main propulsion diesel engines would normally be fitted with a/an __________.
  79. #591 The direct acting mechanical governor used with some small diesel engines, controls fuel flow to the engine by __________.
  80. #592 The governor, shown in the illustration, will have its preset speed droop altered whenever __________. Illustration MO-0092 illustration
  81. #593 As the load is being decreased on the engine controlled by the governor shown in the illustration, the __________. Illustration MO-0092 illustration
  82. #594 In a simple hydraulic governor with speed droop, oil under pressure is maintained ready for use in the __________.
  83. #596 The function of the synchronizing motor on the generator governor illustrated is to __________. Illustration MO-0092 illustration
  84. #601 Which of the listed conditions will result in the failure of an auxiliary diesel engine to shut down?
  85. #604 Ethylene glycol, when used as a coolant in a closed cooling system for a diesel engine, is more advantageous than untreated raw water because it _____...
  86. #605 If the coolant temperature is too low as it passes through internally cooled fuel injectors, the injectors can be damaged by __________.
  87. #607 The most common contaminate of governor hydraulic fluid is __________.
  88. #608 If a hydraulic governor has been refilled with oil, the engine should be operated until it reaches normal temperature, then the air should be purged,...
  89. #609 Adjustments to the compensating needle valve in a hydraulic governor should be made with the engine at __________.
  90. #611 What is the normal bearing clearance permitted at the horizontal axis of the shaft for the bearing shown in the illustration? Illustration MO-0121 illustration
  91. #612 After following the prescribed procedures to measure the thrust bearing clearance shown in the illustration, the distance "F" is determined to be 200... illustration
  92. #613 Because of the close tolerances used in diesel engine fuel oil pumps, a worn plunger requires __________.
  93. #614 When a nozzle tester is being used to test a "closed" type fuel injection nozzle, a clogged nozzle orifice will be indicated by a __________.
  94. #615 Which of the fuel nozzles listed requires the LEAST maintenance?
  95. #616 When running a large, dual fuel, main propulsion diesel engine on heavy fuel, which of the following precautions should be observed when switching fro...
  96. #617 Air is normally bled from a diesel engine fuel system by __________.
  97. #618 The spray holes in diesel engine fuel valves should be cleaned using carbon solvent and __________.
  98. #619 The insertion of shims between the foot of a marine type connecting rod and a bearing box would result in __________.
  99. #620 After a long period of operation, a wear ridge, caused by piston ring action, will develop near the top of the cylinder liner. This ridge must be remo...
  100. #621 When a piston is removed from a diesel engine for maintenance, the piston should be examined for __________.

Motor Plants and Auxiliary Boilers questions: what to expect

Q How many Motor Plants and Auxiliary Boilers questions are in the Engine pool?

There are 1,433 Motor Plants and Auxiliary Boilers questions on this site, every one released by the U.S. Coast Guard or taken from the National Maritime Center's sample examinations, with its correct answer. The exam draws its Motor Plants and Auxiliary Boilers module from the same pool.

Q What score do I need to pass the Motor Plants and Auxiliary Boilers module?

Most USCG exam modules, including Motor Plants and Auxiliary Boilers, require 70 percent to pass. Rules of the Road modules require 90 percent.

Q Are these the real USCG Motor Plants and Auxiliary Boilers exam questions?

Yes. They are the published U.S. Coast Guard questions, matched to the National Maritime Center's 2026 sample examinations. Answer any question to see the correct choice, the USCG reference and the illustration where the question uses one.

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