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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 101–200 of 1,433 · page 2 of 15

  1. #172 Which of the following conditions is most likely to occur if the electric starter motor pinion gear fails to disengage from the flywheel of a diesel e...
  2. #173 When starting air is admitted, a diesel engine turns over very slowly without firing. The cause may be __________.
  3. #174 When an additional load is applied to a diesel engine which is using an inadequately inflated air bladder clutch unit, you can expect __________.
  4. #175 Misalignment of the drive shaft and propeller shaft flanges can be detected by using a dial indicator or __________.
  5. #176 One of the most common causes of reduction gear failure is gear wear caused by scoring as a result of __________.
  6. #177 In a diesel engine, a leaking exhaust valve can cause __________.
  7. #178 A dry-type exhaust silencer clogged with soot, will cause __________.
  8. #180 Black smoke exhausting from an operating diesel engine is an indication of poor combustion which may be caused by __________.
  9. #183 Maintaining the lowest possible scavenging air temperature at all times is not recommended due to the possibility of the __________.
  10. #187 An operating diesel engine that suddenly loses power, is due to a/an __________.
  11. #191 Which of the following conditions is indicated by the presence of water in the scavenging air receiver?
  12. #193 When calculating the indicated power developed in a diesel engine cylinder, 1 horsepower is equivalent to '33,000 foot-pounds per minute'. What conver...
  13. #195 A diesel engine indicator diagram has an area of 22 cm2 and a length of 12.5 cm. If the scale of the indicator spring is 1 mm = 1 kg/cm2, what is the...
  14. #199 A diesel engine cylinder has a swept volume of 125 cubic inches and a compression ratio of 13.5 to 1. What is the clearance volume in the cylinder at...
  15. #202 Line "P" in the illustration is the __________. Illustration MO-0126 illustration
  16. #204 The diagram shown in the illustration may be used to determine the proper operation of the engine. Which of the following statements represents an acc... illustration
  17. #205 Which of the following conditions would NOT be considered a valid reason for the diesel engine to operate in the area indicated by letter "B" shown in... illustration
  18. #206 In the pressure-volume diagram shown in the illustration, fuel injection occurs at point __________. Illustration MO-0035 illustration
  19. #207 An indicator card or pressure-volume diagram, shows graphically the __________.
  20. #209 On the indicator card shown in the illustration, lines 'A' and 'B' indicate __________. Illustration MO-0108 illustration
  21. #211 In the pressure-volume diagram, shown in the illustration, the volume line is divided into 16 units indicating __________. Illustration MO-0035 illustration
  22. #212 In the pressure-volume diagram shown in the illustration, curve 'A-d' indicates __________. Illustration MO-0035 illustration
  23. #213 In the pressure-volume diagram, shown in the illustration, what is indicated to have occurred by the line connecting points 'd' and 'e'? Illustration... illustration
  24. #214 On the cylinder indicator diagram illustrated, the dotted line indicated as 'L' is describing the _________. Illustration MO-0033 illustration
  25. #215 Which of the indicator diagrams illustrated depicts the condition that should be corrected by retarding only the timing? Illustration MO-0029 illustration
  26. #216 On the indicator card shown in the illustration, lines 'A' and 'B' indicate __________. Illustration MO-0108 illustration
  27. #217 Diesel engines are classified as reciprocating internal combustion engines because they __________.
  28. #218 What determines the number of events occurring in a cycle of operation in an internal combustion engine?
  29. #219 The thermal energy produced by an internal combustion engine is transformed into __________.
  30. #220 In describing engine operation, what does the term "cycle" mean?
  31. #221 The highest pressure in a diesel engine cylinder normally occurs __________.
  32. #222 Modern marine diesel engines equipped with mechanical fuel injection operate on a combustion cycle which is __________.
  33. #223 The load is always placed on the lower half of the main bearings in a/an __________.
  34. #224 The camshaft drive is designed to maintain proper camshaft speed relative to crankshaft speed. In maintaining this relationship, the camshaft drive ca...
  35. #225 Which of the terms listed below represents the operational speed at which excessive engine vibration is created?
  36. #226 The bore of a diesel engine cylinder describes the __________.
  37. #227 The cubic inch (or liter) displacement of a cylinder is determined by the diameter of the piston and the __________.
  38. #228 The compression ratio of a diesel engine refers to the ratio between the __________.
  39. #229 If the compression ratio is increased on any diesel engine, __________.
  40. #230 The theoretical minimum compression ratio necessary to ensure compression ignition in a direct injection diesel engine is __________.
  41. #232 The ratio of the brake horsepower to the indicated horsepower of a diesel engine is its __________.
  42. #233 The most important factor in engine performance is the actual power output at the end of the crankshaft available for doing work. This is known as ___...
  43. #234 The average pressure exerted on a piston during each power stroke is termed __________.
  44. #235 Most practical diesel engines today operate on a cycle which is a combination of the Diesel and Otto cycles. In this process, compression ignition ___...
  45. #236 The pressure-volume diagrams illustrated are of four internal combustion engine cycles. Which one represents the theoretical diesel cycle? Illustratio... illustration
  46. #237 If point #1 in the diagram shown is the beginning of gas compression, which of the cycles listed is being illustrated? Illustration MO-0036 illustration
  47. #238 The minimum fuel oil delivery pressure required for efficient injection depends primarily on the __________.
  48. #239 Fuel injection systems are designed to primarily meter fuel, atomize fuel, and __________.
  49. #240 The degree of fuel atomization in a diesel engine cylinder depends primarily on __________.
  50. #241 The purpose of the delivery check valve used in a diesel fuel injection jerk pump is to __________.
  51. #242 Injection pressure in a common rail fuel system is controlled by __________.
  52. #246 According to the illustration, initial timing of fuel injection into the cylinder is controlled with the component that is identified as the letter __... illustration
  53. #247 According to the illustration, fuel cutoff timing in the cylinder is controlled with the component that is identified as the letter _________. Illustr... illustration
  54. #249 The amount of fuel delivered by a unit injector is controlled by the __________.
  55. #250 In a unit injector, an upper helix and lower helix are machined in the lower part of the plunger for __________.
  56. #251 The control rack to a unit injector regulates fuel delivery by __________.
  57. #255 A normally operating diesel engine is shutdown by __________.
  58. #256 Load control on a diesel engine is accomplished by __________.
  59. #257 Diesel engine automated control systems may utilize sensing devices of dual function, with sensing ranges providing both alarm and engine shut down ca...
  60. #260 Which of the following statements describes the operation of the circuit shown in the illustration? Illustration MO-0114 illustration
  61. #261 The device represented by the symbol "B" in the illustration is used to __________. Illustration MO-0115 illustration
  62. #263 In the reversing reduction gear shown in the illustration, the forward and reverse main pinions are in constant mesh with the main gear. This means th... illustration
  63. #264 Reduction gear casings are vented in order to __________.
  64. #265 A diesel engine with a full speed of 1000 RPM drives a propeller at 300 RPM. What is the speed reduction ratio?
  65. #266 The main engine thrust bearing shown in the illustration contains how many thrust shoes? Illustration MO-0121 illustration
  66. #268 What type of bearing is shown in the illustration? Illustration MO-0120 illustration
  67. #270 The minimum speed an engine must attain before ignition can occur depends upon __________.
  68. #271 Heat for igniting the fuel oil in the cylinder of a diesel engine is generated by the __________.
  69. #272 The main operating characteristic of diesel engines which distinguishes them from other internal combustion engines is the __________.
  70. #273 Theoretical perfect combustion in a diesel engine yields by-products of __________.
  71. #274 The formation of carbon monoxide in diesel exhaust gases is reduced by __________.
  72. #275 Turbulence of the compressed air charge in a diesel engine cylinder increases __________.
  73. #276 In a diesel engine, after ignition of the fuel occurs, but before the piston reaches TDC, there is little change in the cylinder __________.
  74. #277 In the starting process of a diesel engine, the main object is to attain the compression conditions sufficient to __________.
  75. #278 The greatest turbulence in a diesel engine cylinder is created by the __________.
  76. #279 What is the term given to the process of breaking up fuel oil into very fine particles for better combustion?
  77. #280 Proper atomization of fuel in diesel engine combustion chambers will __________.
  78. #281 Fuel oil penetration into the cylinder of a diesel engine is __________.
  79. #282 Fuel droplets injected into a diesel engine cylinder must have adequate penetration to __________.
  80. #283 Maintaining the proper fuel oil temperature will result in __________.
  81. #284 A diesel engine operating at a light load, when compared to operating at heavy load has an air/fuel ratio that is __________.
  82. #285 As engine RPM is increased from idle speed to full load speed, which of the conditions listed will decrease?
  83. #286 The time between injection and ignition of the fuel is known as __________.
  84. #287 When is fuel injected into a cylinder of diesel engines?
  85. #288 For a given fuel, a change in the compression ratio will affect the ignition lag by which of the listed means?
  86. #290 The rate of pressure rise during the period following fuel ignition in a diesel engine is influenced by the length of the ignition delay period and th...
  87. #291 The pressure in an operating diesel engine cylinder continues to rise for a short period after the piston passes top dead center as a result of the __...
  88. #293 Which statement about diesel engine combustion is true?
  89. #294 Fuel combustion in a diesel engine cylinder should begin just before the piston reaches top dead center and should __________.
  90. #295 On the cylinder indicator diagram illustrated, the dotted line indicated as 'L' is describing the _________. Illustration MO-0033 illustration
  91. #296 Which area of the indicator diagram illustrated, indicates the afterburning period in a diesel engine cylinder? Illustration MO-0033 illustration
  92. #297 Item labeled 'R' as shown in section 6 of the illustration is identified as the __________. Illustration MO-0025 illustration
  93. #298 In the illustrated engine, the fuel camshaft gear drive housing is indicated as letter __________. Illustration MO-0003 illustration
  94. #299 In a large, slow-speed, main propulsion diesel engine, which of the parts listed is under tension when the engine is running?
  95. #300 In the diesel engine illustrated, what part is under compression when firing is taking place in a particular cylinder? Illustration MO-0003 illustration
  96. #303 In diesel engines designed with a crosshead, the motion of the piston rod can be described as __________.
  97. #305 In a large slow-speed propulsion diesel engine, the side thrust on the crosshead is the direct result of _____.
  98. #306 While underway, which of the following would be the FIRST step in reversing a direct reversing large, slow-speed, main propulsion, diesel engine?
  99. #307 In a large slow-speed propulsion diesel engine, the force applied to the piston is __________.
  100. #308 Cast iron pistons used in large propulsion diesel engines are constructed with __________.

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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