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Retired questions · Motor Plants and Auxiliary Boilers
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Engine · 159 questions

Retired questions · Motor Plants and Auxiliary Boilers - USCG Exam Questions

These are retired questions the Coast Guard no longer draws exams from. They stay online for reference; the current questions are in Motor Plants and Auxiliary Boilers.

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 Retired questions · Motor Plants and Auxiliary Boilers questions

Questions 1–100 of 159 · page 1 of 2

  1. #2 Forcing the exhaust gases from the cylinder of an operating two cycle diesel engine with the aid of a blower is known as __________.
  2. #11 At rated engine load and RPM, the diesel engine turbocharger is powered by __________.
  3. #12 The operating speed of a turbocharger is directly dependent upon __________.
  4. #14 What statement is true concerning the charge air system of a modern turbocharged slow- speed two-stroke cycle diesel engine?
  5. #15 On a typical turbo-charged marine diesel engine, what type of blower/compressor is used within the turbocharger?
  6. #21 The highest pressure in any closed diesel engine freshwater cooling system is at the __________.
  7. #22 The expansion tank in a diesel engine closed freshwater cooling system is located at __________.
  8. #23 A closed freshwater cooling system is commonly used with marine diesel engines because the __________.
  9. #25 Sacrificial zinc anodes are used on the saltwater side of diesel engine heat exchangers to __________.
  10. #26 When checking zincs in a saltwater cooled heat exchanger, you should __________.
  11. #27 In a diesel engine jacket water cooler, with seawater cooling the fresh water, the __________.
  12. #33 The theoretical minimum compression ratio necessary to ensure compression ignition in a direct injection diesel engine is __________.
  13. #43 In the illustrated diesel engine, which label points to the piston? MO-0122 illustration
  14. #44 The diesel engine wrist pin in the illustration is indicated by the component labeled __________. MO-0122 illustration
  15. #48 Component "U" of the diesel engine shown in the illustration is called the __________. MO-0122 illustration
  16. #51 The diesel engine component labeled "3", shown in the illustration is called the __________. MO-0122 illustration
  17. #61 Hydraulic couplings will transmit torque equal to the input torque by means of energy changes in a rotating vortex of liquid. For the vortices to form...
  18. #66 The bearing shown in the illustration is designed to carry thrust when applied __________. Illustration MO-0001 illustration
  19. #68 Kingsbury thrust bearings are lubricated by __________.
  20. #69 On a large diesel engine installation, crankshaft axial alignment is maintained by the __________.
  21. #70 Fuel is admitted to a diesel engine cylinder through the __________.
  22. #74 The illustrated device is operated directly by __________. MO-0041 illustration
  23. #77 Which of the fuel injection systems listed uses a spring loaded differential spray needle valve and an individual pump for each cylinder?
  24. #81 Valve '1', as shown in the illustration when, should be operated when __________. Illustration MO-0077 illustration
  25. #88 What is the function of the after coolers installed in the diesel engine air intake system?
  26. #89 The section of the turbocharger which would be connected to the after cooler inlet is labeled __________. MO-0080 illustration
  27. #92 Lube oil cannot be efficiently filtered i f it¶s __________.
  28. #95 The lube oil strainer shown in the illustration is used on the reduction gear of a mid-size diesel engine. The strainer elements consist of __________... illustration
  29. #105 In an auxiliary diesel engine "by-pass type" lubricating oil system, the main lube oil pump forces __________.
  30. #106 Lubrication for the main reduction gears used with diesel engines is usually supplied by __________.
  31. #119 A Bendix drive starting motor disengages the drive gear from the flywheel by __________.
  32. #123 During the starting of a diesel engine, compression gases are prevented from backing into the air starting system, shown in the illustration, by the _... illustration
  33. #139 As shown in the illustration, the function of component "1" is to ________. MO-0128 illustration
  34. #140 As shown in the illustration, what component would normally be installed at location "D? MO-0128 illustration
  35. #159 The color of the diesel engine detergent type lube oil in an operating diesel engine is black, this indicates __________.
  36. #161 When a leak has developed in the lube oil cooler of an operating diesel engine, which of the listed operating conditions can be expected to occur?
  37. #167 A modern centrifuge, similar to the device shown in the illustration, is opened for periodic cleaning. The most common cause of operating failure afte... illustration
  38. #179 White smoke exhausting from a diesel engine can result from __________.
  39. #182 QA main propulsion diesel engine is operating at 80% load and normal speed while the vessel is in calm seas. As the intensity of the seas increase, th...
  40. #184 The power output of a turbocharged diesel engine will drop if the cooling water flow through the after cooler is interrupted because the __________.
  41. #185 Which condition indicates the air side fouling of an after cooler on a turbocharged diesel engine?
  42. #186 Which of the following problems can cause an above normal air temperature to develop in the intake manifold of a turbocharged and after cooled diesel...
  43. #189 A sudden power loss from a turbocharged and after cooled diesel engine is an indication of a/an __________.
  44. #190 A thin film of oil on the lobes of a Roots-type blower indicates __________.
  45. #196 A six cylinder, two stroke/cycle diesel engine is 83% efficient and has a cylinder constant of 0.998 while operating with a mean effective pressure of...
  46. #197 An eight cylinder, four stroke/cycle, single acting diesel engine has a 650 mm bore and a 1400 mm stroke. What will be the developed indicated metric...
  47. #231 Which of the following relationships exists between the temperatures developed in a combustion space, and the compression ratio of the engine?
  48. #248 Regarding the fuel injector shown in the illustration, the purpose of piece No. 38 is to __________. Illustration MO-0059 illustration
  49. #253 A main propulsion diesel engine is normally shut down by __________.
  50. #254 The over speeding of the diesel engine driving an electric generator could cause __________.
  51. #259 The symbol with the output 'ee' shown in the illustration, is properly called a blocking valve. Which of the following statements describes its functi... illustration
  52. #269 What prevents the thrust bearing blocks shown in the illustration from rotating within the housing? Illustration MO-0120 illustration
  53. #313 Which letter represents the scavenging air system non-return valve in the illustration? MO-0003 illustration
  54. #315 In the diesel engine shown in the illustration, the purpose of the part labeled "P" is to __________. MO-0003 illustration
  55. #318 The part labeled "X" shown in the illustration is a __________. MO-0003 illustration
  56. #328 The fuel injector for the diesel engine shown in the illustration, is identified as _________. MO-0122 illustration
  57. #330 Device 'E' shown in the illustration is known as the __________. Illustration MO-0122 illustration
  58. #334 Item '17' in the illustration is the dipstick. When should the length of the dipstick be changed? Illustration MO-0122 illustration
  59. #418 In a by-pass type lubrication system for a diesel engine, the dirty oil line to the centrifuge should be taken from the __________.
  60. #429 The component labeled as part #20 in the illustration is used to __________. Illustration MO-0050 illustration
  61. #439 Wristpin bearings are difficult to lubricate because of their oscillating motion and __________.
  62. #461 If a particular liquid has a specific gravity of .96kg/dm3 at 77°F, what will be the specific gravity of the liquid, as determined from the graph show... illustration
  63. #469 Which of the following precautions should be taken prior to starting the separator shown in the illustration? MO-0127 illustration
  64. #470 How is oil supplied to the device shown in the illustration? MO-0127 illustration
  65. #499 From the graph shown in the illustration, determine the size of the regulating ring required for the proper operation of the fuel oil centrifuge if th... illustration
  66. #500 Using the graph shown in the illustration, the oil being separated has a specific gravity of .87 kg/dm3 at 72.5°C. What will be the specific gravity i... illustration
  67. #501 From the graph shown in the illustration, if the separating temperature required is to be 167°F, and the specific gravity of the oil is .98 kg/dm3 at... illustration
  68. #502 The replacement piping for diesel engine high pressure fuel systems must be the same length and diameter as the original piping to __________.
  69. #514 What is the function of the after coolers installed in the diesel engine air intake system?
  70. #529 In a diesel engine jacket water cooler, with seawater cooling the fresh water, the __________.
  71. #530 Using a cooling water temperature of 225°F (107.2°C), instead of 180°F (82.2°C) in an auxiliary diesel engine, will __________.
  72. #532 Diesel engine jacket water is used in the fresh water distillation process as the __________.
  73. #533 What would be considered a normal temperature increase between the inlet and outlet jacket cooling water of a medium or high-speed diesel engine opera...
  74. #534 Which operating parameter may need to be decreased when running a large main propulsion diesel engine at low load conditions?
  75. #535 As a general rule, what would be the recommended operating water jacket outlet temperature range for medium speed marine diesels set up with closed tr...
  76. #536 In a diesel engine closed freshwater cooling system, the cooling water pressure drop through the engine is 10 psig, and the pressure drop through the...
  77. #540 The outlet from an expansion tank of a closed freshwater cooling system should be piped to the __________.
  78. #545 The operation of the lube oil cooler, shown in the illustration as item #4, will be characterized by which of the following statements? Illustration M... illustration
  79. #575 Which of the turbo charging systems listed operates with the least average back pressure in the exhaust manifold?
  80. #576 Which of the turbo charging methods listed directs the exhaust gases to the turbine at fairly uniform velocity and pressure?
  81. #580 Which of the operating characteristics listed is correct concerning the blower shown in the illustration? Illustration MO-0082 illustration
  82. #597 If governor Item #19 in the illustration were to break on a diesel engine operating under full load, the engine RPM will __________. Illustration MO-0... illustration
  83. #598 In the illustrated auxiliary diesel engine governor, decreasing the distance between piece #6 and piece #10 will affect the engine by __________. Illu... illustration
  84. #600 What is the best way of stopping an over speeding diesel engine?
  85. #602 Sacrificial zinc anodes are used on the saltwater side of diesel engine heat exchangers to __________.
  86. #603 Which of the listed effects would mixtures of ethylene glycol and phosphate compounds have on the metal surfaces of the cooling system of a diesel eng...
  87. #610 When installing the bearing cap on the device shown in the illustration, which of the precautions listed must be observed? Illustration MO-0121 illustration
  88. #632 Diesel engine exhaust gas temperatures can be used to determine individual cylinder __________.
  89. #639 A diesel engine experiences a sudden loss in speed, accompanied by black exhaust smoke, with the fuel rack at maximum, and the speed remaining below n...
  90. #647 As shown in the illustration, which of the following conditions would be responsible for a "low pressure in oil outlet" alarm to be indicated? Illustr... illustration
  91. #658 The thrust bearing shown in the illustration has over eight years of ahead running time. Measurements show "i1" is 4 mm and "i2" is 1mm. Which of the... illustration
  92. #671 Excessive wear at part #11, shown in the illustration would result in __________. Illustration MO-0027 illustration
  93. #677 The thrust bearing shown in the illustration has over eight years of ahead running time. Measurements show "i1" is 4 mm and "i2" is 1mm. Which of the... illustration
  94. #685 A diesel engine operates erratically, over speeds, and fails to restart when cranked at normal speed. Which of the following problems is the most like...
  95. #688 The power output of a turbocharged diesel engine will drop if the cooling water flow through the after cooler is interrupted because the __________.
  96. #705 The item labeled "T" as shown in figure 4 of the illustration is identified as the __________. Illustration MO-0025 illustration
  97. #708 If the speed of the propeller is 135 RPM, the speed of the engine camshaft shown in the illustration will be __________. MO-0003 illustration
  98. #709 Which construction detail is apparent in the connecting rod and piston assembly shown in the illustration? MO-0011 illustration
  99. #710 The illustration shown describes a _______. MO-0069 illustration
  100. #711 Which of the following statements is correct concerning the connecting rod and piston assembly shown in the illustration? MO-0011 illustration

Motor Plants and Auxiliary Boilers questions: what to expect

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

This retired set holds 159 Motor Plants and Auxiliary Boilers questions the Coast Guard no longer draws on exams. They stay online for reference; the current Motor Plants and Auxiliary Boilers module is the one to study.

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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