marine engineering course for yatch engines

This presentation was prepared for the Yacht Engines course at Piri Reis University.

1. Marine Engineering Dr. Lec . Abdullah Köktürk [email protected] [email protected] 0543 423 06 53

2. Diesel engines The diesel engine is a type of internal combustion engine which ignites the fuel by injecting it into hot, high-pressure air in a combustion chamber. In common with all internal combustion engines the diesel engine operates with a fixed sequence of events, which may be achieved either in four strokes or two, a stroke being the travel of the piston between its extreme points. Each stroke is accomplished in half a revolution of the crankshaft . 4

3. Diesel Engine Components Main parts structural parts (stationary p.) running parts Systems 5

4. Structural parts PURPOSE: to support running parts to keep them in position and line to provide jackets and passages for cooling water, sumps, for lube oil to form protective casing for running parts to support auxiliaries (valves, camshaft, turbo blowers) 6

5. Running parts PURPOSE - to convert the power of combustion in the cylinders to mechanical work 7

6. Systems PURPOSE Supply of air Removal of exhaust Turbocharging Supply and injection of fuel Lubrication Cooling 8

7. Structural parts bedplate frame or column engine or cylinder block cylinder liners cylinder head or cover 9

8. Bedplate foundation on which the engine is built must be rigid enough to support the rest of the engine and hold the crankshaft which sits on the bearing housing in alignment with transverse girders at . On the small bore engines, the bedplate can be made from cast iron as a single casting. Larger engines have a fabricated bedplate . 10

9. Bedplate 11

10. Frame - crankcase load-carrying part of an engine it may include parts as the cylinder block,base, sump and end plates in two-stroke engines, frames are sometimes known as A-frames 12

11. Frame - crankcase 13

12. Cylinder Block = engine block part of the engine frame that supports the engine cylinder liners, heads and crankshafts cylinder blocks for most large engines are made of castings and plates that are welded horizontally and vertically for strength and rigidity (stiffener) entablature = cylinder block which incorporates the scavenge air spaces in two-stroke engines 14

13. Cylinder Block 15

14. Cylinder liner a bore in which an engine piston moves back and forth replaceable the material of the liner must withstand extreme heat and pressure developed within the combustion space at the top of the cylinder, and at the same time must permit the piston and its sealing rings to move with a minimum of friction - Dry liner - Wet Liner 16

15. Cylinder liner 17 Dry layner Wet liner

16. Cylinder head = cylinder cover the space at the combustion chamber top is formed and sealed by a cylinder head the cylinder head of a four-stroke engine houses intake and exhaust valves, the fuel injection valve, air starting val v e, safety valve ( the two-stroke engine lacks the intake valve ) 18

17. Cylinder head - cylinder cover 19

18. Cylinder head - cylinder cover 20

19. Major running parts piston piston rod crosshead connecting rod crankshaft & its bearings 21

20. Piston one of the major moving parts crown skirt must be designed to withstand extreme heat and combustion pressure made of cast iron or aluminium (to reduce weight) 22

21. Piston 23

22. Piston rod connects the piston with the crosshead 24

23. Crosshead the crosshead pin connects the piston rod to the connecting rod 25

24. Crosshead 26

25. Connecting rod it is fitted between the crosshead and the crankshaft it transmits the firing force, and together with the crankshaft converts the reciprocating motion to a rotary motion 27

26. Connecting rod 28

27. Crankshaft & its bearings one of the largest moving parts it consists of a series of cranks formed in a shaft converts reciprocating motion of the piston into rotary motion counterweights for balancing purposes 29

28. Crankshaft 30

29. Crankshaft 31

30. Crankshaft 32

31. Bearings 33 A journal bearing : provides support normal to the axis of rotation A thrust bearing : provides support along the axis of rotation

32. Arrangements for the air supply and gas exhaust: valves (inlet & exhaust), c amshaft & camshaft drive, push rod, rocker arm, spring manifolds, scavenging and supercharging (turboblower systems ) 34

33. Fuel injection system fuel pump, high pressure piping, injector, nozzle 35

34. Engine Parameters Cylinder bore – inner diameter of the cylinder (in mm or cm) Stroke – the di s tance the piston travels between top and bottom dead centers (in mm or cm) Engine speed – speed at which the crankshaft rotates (measured in revolutions per minute) 36

35. 37

36. Four-stroke cycle 38 The four-stroke cycle is completed in four strokes of the piston, or two revolutions of the crankshaft.

37. Four-stroke cycle 39 https://www.youtube.com/watch?v=s2WGFELXPNg

38. Four-stroke cycle 40 TDC (top dead center) BDC (bottom dead center)

39. Four-stroke cycle 41 Intake Compression Power (Expansion-Combustion) Exhaust

40. The four-stroke engine 42 https://www.youtube.com/watch?v=DZt5xU44IfQ&t=135s

41. The two-stroke cycle 43 The two-stroke cycle is completed in two strokes of the piston or one revolution of the crankshaft

42. The two - stroke engine 44

43. The two-stroke engine 45

44. Comparison of two-stroke and four-stroke cycles The differences between two- and four-stroke-cycle petrol engines regarding the effectiveness of both engine cycles are given below: a) The two-stroke engine completes one cycle of events for every revolution of the crankshaft, compared with the two revolutions required for the four-stroke engine cycle. b) Theoretically, the two-stroke engine should develop twice the power compared to a four-stroke engine of the same cylinder capacity. c) In practice, the two-stroke engine's expelling of the exhaust gases and filling of the cylinder with fresh mixture brought in through the crankcase is far less effective than having separate exhaust and induction strokes. Thus the mean effective cylinder pressures in two-stroke units are far lower than in equivalent four-stroke engines. . d) There are fewer working parts in a two-stroke engine than in a four-stroke engine, so two-stroke engines are generally cheaper to manufacture. 46

45. The gas exchange process A basic part of the cycle of an internal combustion engine is the supply of fresh air and removal of exhaust gases. This is the gas exchange process. Scavenging is the removal of exhaust gases by blowing in fresh air. Charging is the filling of the engine cylinder with a supply or charge of fresh air ready for compression. With supercharging a large mass of air is supplied to the cylinder by blowing it in under pressure. Older engines were ‘naturally aspirated’- taking fresh air only at atmospheric pressure. Modern engines make use of exhaust gas driven turbo- chargers to supply pressurized fresh air for scavenging and supercharging. Both four-stroke and two-stroke cycle engines may be pressure charged. On two-stroke diesels an electrically driven auxiliary blower is usually Provided because the exhaust gas driven turbo blower cannot provide enough air at low engine speeds, and the pressurized air is usually cooled to increase the charge air density. A turbocharger is an air compressor driven by exhaust gas . The single shaft has an exhaust gas turbine on one end and the air compressor on the other. Suitable casing design and shaft seals ensure that the two gases do not mix. Air is drawn from the machinery space through a filter and then compressed before passing to the scavenge space. 47

46. Turbocharcher 48

47. Turbocharcher 49

48. Power measurement 50 Torque In physics, torque (or often called a moment) can informally be thought of as "rotational force" or "angular force" which causes a change in rotational motion. This force is defined by linear force multiplied by a radius. The SI units for torque are Newton metres. In the U.S., foot-pounds force (ft-lb) The force applied to a lever, multiplied by its distance from the lever's fulcrum, is the torque .  = r x F r : Particle's position vector F : Force acting on the particle Or, more generally, torque can be defined as the rate of change of angular momentum ; dL  = ---- dT L : Angular momentum vector t : Time. p : Linear momentum vektor

49. Relationship between torque, power and energy Power = torque x angular speed Power = torque x 2  x rotational speed Torque (Nm) x  x angular speed (rpm) Power (Kw) = ------------------------------------------------ --------------------- 30000 Torque ( lbf -f) x angular speed (rpm) Power ( hp ) = ------------------------------------------------- ------------------ 5252 51

50. Standard Operating Practice Unlike a gas engine, a diesel engine has no ignition system or spark plugs. Instead, diesel fuel ignites “spontaneously” when sprayed into air that has been superheated by compression within a cylinder. This combustion then generates a power stroke. Thus there are three preconditions for a diesel engine to work: 1. An adequate supply of combustion air . 2. Compression of this air until its temperature rises above the ignition point of diesel 3. Injection of diesel fuel into this cylinder of heated air at a moment that is precisely coordinated with the movement of the pistons up and down the cylinders. Given air , adequate compression, and proper fuel injection , a diesel engine more or less has to run. Routine maintenance is designed to guarantee these three preconditions; troubleshooting focuses on finding out which of them is missing. 52

51. Standard Operating Practice 53 Immediately after the engine fires, be sure the oil pressure gauge is normal or the oil pressure warning light is out. Also be sure that the alternator is charging (i.e., either the ammeter shows charging or the light is out) and that cooling water is coming out of the exhaust. Before cranking the engine with the starter motor, check the oil level and the freshwater level. Also be sure the raw-water seacock is open, the raw water strainer is unobstructed, the transmission is in neutral.

52. Standard Operating Practice An engine that does not crank almost always has an electrical problem but occasionally has water in the cylinders ). An engine that cranks slowly and fails to start is probably not compressing the air in the cylinders sufficiently to attain ignition temperatures— the cranking speed will need to be increased . An engine that cranks at normal speeds and does not start likely has one of the following: a fuel supply problem ; an obstruction of the air inlet or exhaust; or a serious lack of compression . The latter requires a rebuild, and is particularly likely with an engine that has high operating hours, especially if it is harder to start in cold weather . 54

53. Engine Cranks Slowly or Not at All 55 Turn on the ignition, but do not crank. Place the ‘+’ probe of a DC voltmeter on the terminal at which the battery positive cable connects to the starter motor solenoid ① and the ‘–’ probe on the cranking battery negative post (or engine block if the negative post is not accessible): ● Higher than 12.6 volts: OK ● 12.4 to 12.6 volts: the battery is somewhat discharged ● 12.2 to 12.4 volts: the battery needs recharging ● Below 12.2 volts: the battery is almost completely discharged and needs recharging ● No volts: a battery isolation switch is probably turned off! Assuming a charged battery, put the meter probes as in (1) and have someone attempt to crank the engine: ● If the voltage remains the same, either the ignition circuit is defective or the solenoid is out of action.

54. Engine Cranks Slowly or Not at All 56 To investigate further, connect a jumper wire or screwdriver blade from the starter motor cable terminal on the solenoid to the ignition switch terminal (the one with a relatively small cable going into the wiring harness ②). If the engine cranks, the switch circuit is defective. If it does not crank, use a screwdriver blade to short the two big terminals on the solenoid ➂ If the starter motor spins (the engine will probably still not crank), the solenoid needs rebuilding (remove the end cover and check the points). No response means the battery is dead (check it again) or the starter motor is inoperative.

55. Engine Cranks Slowly or Not at All If the voltage falls a volt or two but then stabilizes, feel all connections and cables in the cranking circuit (positive and negative). If any connections are warm , undo them , clean the terminals, and reconnect . If any cables are warm, they are undersized and need replacing with larger cables . If the voltage collapses, the battery is dead or has no remaining capacity, or the starter motor is shorted, or the engine is seized or full of water . Place a socket on the crankshaft pulley nut and attempt to turn the engine over. If it will not turn, the engine is seized or full of water. 57

56. Engine Cranks Slowly or Not at All Many cranking circuits on boats suffer from excessive voltage drop as a result of undersized cables. To test this, place the ‘+’ probe of a DC voltmeter on the cranking battery ‘+’ post, and the ‘–’ probe on the terminal at which the starter motor ‘+’ cable or strap attaches to the solenoid ④and crank. Note the reading. Now place the ‘+’ meter probe on the starter motor case and the ‘–’ probe on the battery negative terminal ⑤ and crank. Note the reading. If either reading is above 0.5 volt, there is excessive voltage drop. Clean all the terminals and try again. If a high reading persists, fit larger cables. 58

57. Engine Cranks Slowly or Not at All When a previously working engine seizes on start-up, suspect water intrusion into the cylinders . In an emergency, to clear the cylinders, If the crank does not turn on or if it stops turning at any point when the starter motor is flicked on, STOP! You can try turning the crankshaft in tiny increments by placing an appropriate wrench on the crankshaft pulley nut. Once the engine is turning over, change the oil and filter. If there is any sign of water in the oil, run the engine for a few minutes and change the oil and filter again. Do this once more after 25 hours of running time. 59

58. Engine Cranks Normally But Does Not Fire Suspect a problem with the fuel supply or insufficient compression of the air in the cylinders . A complete obstruction of the air supply is less likely. 1. Ensure that there is fuel in the tank and any fuel valves are open . 2. Make sure any engine “stop” device is not activated . (Not all engines have such a device.) 3 . Be sure the air intake and exhaust are unobstructed 4 . If the engine has glow plugs, check to see that they are working 5. Open the throttle wide , crank 10 to 15 seconds , let the engine rest 2 minutes, and crank again . If the engine now fires, it probably has poor compression and needs an overhaul. 6. If the engine is cranking slowly, check the battery and cranking circuit . If these are OK, block the air intake while cranking and then remove the blockage while continuing to crank (this will help the engine to crank faster). 60

59. Engine Overheat If the raw-water flow in the exhaust is normal, check the freshwater pump belt . If that is OK, check the header tank on the freshwater side of the engine (CAUTION: let the engine cool before removing the pressure cap) ①. If the raw-water flow in the exhaust is reduced or absent, shut down the engine, then check the raw-water pump belt (note: some pumps are gear driven and have no belt ). If that is OK, make sure the raw-water intake seacock is open . (If it is not, the raw-water pump impeller may have been destroyed.) Next inspect the raw-water strainer ②. If it is clean: 61 Close the raw-water seacock , disconnect its hose , and momentarily open the seacock to check for a strong flow. If the flow is reduced or absent , there is an obstruction at the raw-water inlet strainer on the outside of the hull .

60. Engine Overheat Remove the raw-water pump cover and check the impeller for cracked or missing vanes ➂ . If any are missing, find the pieces (they will likely be in the heat exchanger). Check the tube stack in the heat exchanger for obstructions (the tube stacks are often accessed by removing covers at one or both ends of the heat exchanger) ④. If an older engine only overheats when heavily loaded or after a move into warmer waters, suspect a scaled heat exchanger. 62

61. Miscellaneous Operating Problem Exhaust Has Blue Smoke A little blue smoke is normal on start-up. If it persists after the engine has warmed, the engine is burning oil and needs an overhaul. Black Smoke A puff or two of black smoke on sudden acceleration is normal for an older engine. In all other circumstances, black smoke indicates improper fuel combustion : 1. Check the air filter or inlet for obstructions . 63 2. Break the exhaust hose loose from the water lift muffler and check for carbon fouling in the exhaust ①. (This photo shows a carbon-free exhaust exit.) If more than a thin film of carbon is present, the exhaust needs cleaning (and the cylinder head and valves also probably need servicing). 3 . If the black smoke only occurs at high engine speeds, check for overloading (a heavily fouled boat bottom, too much auxiliary equipment, etc.). If this is a new boat, the propeller may be over sized.

62. Miscellaneous Operating Problems 64 Misfiring A rhythmic misfiring means that one or more cylinders are losing compression . A misfiring on start-up that stops once the engine is warm suggests that one or more cylinders are losing compression, and the engine needs an overhaul. An irregular misfiring suggests dirty fuel (check for sediment in the base of the fuel filter ②), water in the fuel (check for water in the filter), or plugged fuel filters —especially if the misfiring only occurs at higher engine speeds and loads

63. routine maintenance The great majority of engine problems are caused by a failure to ensure clean fuel or a failure to change the oil at the prescribed intervals. Clean Fuel Dirty fuel is the #1 cause of marine diesel problems. There are four lines of defense to ensure clean fue l: 1. Adequate filtration of everything that goes into the tank . 2 . Take one or more fuel samples from the base of all fuel tanks at least once a year to remove any sediment and water ①, ② 65 3. Change the primary fuel filter at the specified intervals ➂, and clean the tank if the filter is dirty . 4. Change the secondary filter at the specified intervals ④. If the filter is dirty, clean the primary filter and the tank.

64. Additional Routine Maintenance 1. Change the air filter at the prescribed intervals (many small diesels do not have an air filter). 2. Periodically tighten the alternator belt . It should depress no more than 1/2 inch at the center of the longest belt run under moderate finger pressure ⑤. 66 3. Check the heat exchanger for a sacrificial zinc anode (many modern diesels do not have zinc anodes). If present, inspect it monthly until the rate of zinc loss is established. Replace the anode when it is no more than half gone.

65. Changing the Oil Along with ensuring clean fuel, this is essential for long engine life. A marine diesel engine needs an hour meter in the panel so you know when to do oil changes and other maintenance. 1. Run the engine until it is up to normal operating temperature . 2. Pump the oil out of the crankcase with the installed oilchange pump ⑥ or by sucking it out through the dipstick tube ⑦. 67

66. 3. Unscrew the oil filter with the appropriate filter wrench. In the absence of a filter wrench, use a spare alternator drive belt. Catch any spills in a disposable diaper or by placing a plastic bag around the filter ⑧. 4. Lubricate the sealing ring on a new filter with clean oil ⑨ and screw it on until hand tight. Tighten a further one-half to three-quarters turn with the filter wrench. 5. Add oil to the appropriate mark on the dipstick ➉. Crank the engine and check the oil pressure . (It may take a few seconds to come up to normal.) Inspect the sealing area around the new oil filter for leaks. 68 Changing the Oil

67. Bleeding the Fuel System Air Air in the fuel system will stop most diesels. With older engines, air must be removed by bleeding the fuel system as follows: 1. Check for a pump and bleed nipple on the primary filter ①. If present, unscrew the bleed nipple two or three turns and operate the pump until fuel free of bubbles spurts out. 2. If there is no pump on the primary filter, find the engine-mounted fuel lift pump . If electric, turn on the ignition . If manual, find the pump l ever ②. 3 . on the secondary fuel filter and unscrew the nipple a couple of turns ➂. 4. Operate the lift pump until fuel free of air bubbles flows o ut, catching spilled fuel. Then close the nipple. If the air bubbles don’t clear, either the tank is low on fuel or there is an air leak on the suction side of the pump; check the seal on the primary filter first, especially if it has been changed recently. 69 5. Move upstream in the fuel system to the next bleed nipple, which is normally on the injection pump . 6. Once finished, open the throttle wide and crank 10 to 15 seconds. 7. If the engine does not fire, loosen the injector nuts, open the throttle wide, crank until fuel spurts from each loosened connection, and then tighten .

68. https://www.youtube.com/watch?v=ETfjGSnmCeg ( Diesel fuel systems - Part 1 - Changing the filters ) https://www.youtube.com/watch?v=e2VCNPCKQrA ( How To Change A Fuel Filter On A Marine Diesel Engine ) https://www.youtube.com/watch?v=N14ZYhUwdo8&spfreload=1 ( Replacing the Raw Water Pump ) https://www.youtube.com/watch?v=eZYJq746awc ( Raw Water Impeller ) https://www.youtube.com/watch?v=UxLfF2abE_o ( Replacing Your Mercruiser Marine Engine Sea Water Pump Impel ) https://www.youtube.com/watch?v=yAba6BabHPs ( Yanmar Impeller & Coolant Replacement ) https://www.youtube.com/watch?v=gtfiCLc1g6I ( Sailboat engine maintenance: An old Yanmar 2GM20F diesel, let's do an oil change! ) 70 Sailboat engine maintenance videos

69. THE BOATOWNER’S CHECKLIST 1. Record the information from all engines and transmissions ( The transmission, which conveys engine power to the propeller shaft, is often called the marine gear, the gearbox, or simply the gear. ) Every engine and transmission leaves the factory with a serial number plate (Fig. 1.1 ) to enable the ordering of parts and service work. This same plate often provides the engine’s power rating as well. 71 If no serial number plate is visible, begin looking for its original place on the cylinder block. When this is the case, you will have to get serial number information from the boat’s previous owner. You’ll need the model and serial number whenever you call a mechanic for help. . It’s also vital information when ordering parts.

70. THE BOATOWNER’S CHECKLIST 2. Determine if the boat’s transmission has a come-home feature. If it does, know how to engage it. This information will be found in the transmission service manual. 72

71. THE BOATOWNER’S CHECKLIST 3. Locate and clean the transmission oil suction screen and filter, if so equipped. Most hydraulic transmission clutch failures start with a plugged suction screen. A failure is easy to spot early by monitoring any accumulation of metallic debris in the suction screen. 4. Find and check the oil dipsticks for both the engine and the transmission. 5. Learn how to check the coolant level . 6. Check the engine’s direct current (DC) electrical system, including the starter motor, alternator, batteries, starter switch, the DC breaker or fuse panel, the engine and transmission gauges, all interconnecting wires, and often electronic engine and transmission controls. 7. After turning off any battery chargers and all electrical loads, check the electrolyte levels in all liquid-electrolyte batteries with a good light. 73

72. THE BOATOWNER’S CHECKLIST 8. If your boat has a fire suppression system , find its sensors and controls and verify that the bottles are full . 9. Assuming the boat has a engines , locate all valves for both sides of the fuel system ( suction and the return ). 10. Verify that all external fuel tank fill openings are properly sealed . 11. Find the stuffing box ( Fig . 1-4) and learn the best way to adjust it. 74 Most stuffing boxes are designed to admit a slow drip of water, which lubricates the shaft, and the purpose of adjustment is to obtain the proper drip rate. If the drip is too fast, the bilge fills with water; if it is not fast enough, the shaft overheats. Representative stuffing box.

73. THE BOATOWNER’S CHECKLIST 12. Locate and check the condition of the boat’s freshwater tank or tanks , and also look for leaky or damaged hoses or fittings . 13. Find the best method for an emergency engine shutoff on your boat . 14. Locate the bilge pumps and bilge pump switches ( Fig . 1-5), together with their fuses or breakers . Bilge pumps have two possible settings — manual or automatic . Verify that each pump works properly on either setting . 75

74. THE BOATOWNER’S CHECKLIST 15. Locate the engine cooling system’s rawwater strainer and its valves, if so equipped. 16. Locate all openings that pierce the hull and check for visible leaks, signs of corrosion (Fig. 1-7), and adequate tightness of the related fittings and hose clamps. 17. Outboard engines: Check the engine mounting bolts for adequate tightness, fuel lines for kinks or chafing, and steering linkage for excess wear. Also, check all controls and electrical connections for any apparent damage before starting the engine. If the engine is a newer four-stroke outboard, remember that the intake and exhaust valves do need to be adjusted periodically. If the engine is a two-stroke outboard, confirm whether it has automatic oil injection or not. If not, you will have to mix the oil into the fuel with each refueling. Read the engine manual to find the mixing ratio and the type of oil to add to the gasoline. Stock plenty of two-stroke oil on the boat. Watch for corrosion where dissimilar metals meet 76

75. ENGINE START-UP PROCEDURES • Check the engine and transmission oil levels. • Check the coolant level. • Remove the cover from a vertical dry exhaust stack, if your boat is so equipped. • Check the battery charge. • Now crank and start the engine(s), keeping your eyes on the oil pressure gauge to verify that the oil pressure is correct. • Inspect the engine and transmission for leaks and excess noise. • Idle the engine up to 1,000 rpm in neutral. • Make note of the exhaust sound and note the exhaust gas color; it must not be white. • Unless your boat has a dry exhaust, make sure a healthy flow of cooling water is coming out with the exhaust. • When the water (coolant) temperature reaches 100°F, you can put the engine into gear and idle away from the dock. • When the water (coolant) temperature reaches 180°F, you can throttle up the engine to cruising speed. 77

76. TOOLS AND EQUIPMENT TO HAVE ON BOARD 1. Jumper cables 2. A multimeter ( electrical tester ), along with the knowledge to use it 3. Aquarium-grade silicone sealant 3. Rolls of gasket paper in various grades and thicknesses are essential for maintenance and repairs 4. It’s important to carry both stainless steel and high-strength bolts and hardware on oceangoing boats 5. spare oil pressure and water temperature gauges 6. high-quality black and red electrical tape 7. Spare engine- cooling system thermostats are important to have when an engine is running too hot or cold 78

77. Know how to do the following routine procedures • replace the raw-water pump impeller • change the engine and transmission oil filters and fuel filters • change the engine air filter • drain water from the fuel tanks • switch from one fuel tank to the other while under way 79

78. EMERGENCY SCENARIOS 1. First, unless your diesel engine is selfbleeding , learn the procedure for bleeding air from its fuel system . Note : All gasoline engines and some diesel engines have self- bleeding fuel systems . 2. Learn the procedure for bleeding air from your engine’s cooling system after the coolant has been drained and refilled . 3. Know all the possible sources of water that can sink or damage your boat , and know how to halt each one . 80

79. Turn Your Engine into a Bilge Pump By replumbing your engine’s raw-water pump , it is possible to take water from the bilge and pump it overboard . Simply detach the rawwater intake hose from its seacock ( after closing the seacock ) and plunge it into the bilge as shown in the illustration . Of course , this will only work on relatively slow leaks . 81 Replumb the seawater cooling system to pump the bilge

80. Stop a Runaway Diesel Engine One way to quickly stop a runaway diesel engine is to cut off its air supply . Alternatively , if you lack the time or means to shut off the air , the next best thing to do is to break off a vital fuel fitting in the incoming fuel supply plumbing . 82

81. Removing below- FL ush broken bolt S 83

82. KEEP YOURSELF SAFE You should use gloves to protect your hands and skin from chemical compounds . When your work will create loud noises , wear earplugs or other types of ear protection . When you’re grinding or using hazardous chemicals , wear safety glasses and use a full-face shield over the glasses . When you’re grinding or welding , wear leather gloves to protect your hands . Finally , for breathing protection from dust particles and mist , use a respirator with the correct cartridge inserts for the job you are doing . Get a chemical cartridge when appropriate , and a dust and particulate cartridge for grinding wood , fiberglass , or metal. 84

83. UNDERSTANDING MARINE ENGINES Sailboats are typically less than 100 hp and have up to four cylinders . IN-LINE ENGINES Most in- line engines are easy to maintain and keep clean , largely because all the cylinders are lined up in a single row , making them easier to access than on V engines . have only one cylinder head per engine. The cylinders on an in- line engine are numbered starting from the front end , where the water pump is located . The first cylinder is the one closest to the water pump . in- line engines V type engines

84. UNDERSTANDING MARINE ENGINES In marine engines , the front of the engine is always the end opposite the flywheel , and the transmission is always at the rear end , outside the flywheel . 86 a John Deere diesel engine timing gears .

85. ENGINE MECHANISMS AND SYSTEMS Every reciprocating engine must have the following twenty mechanisms and systems : 1. fuel system 11. plumbing system 2. cooling system 12. filtration system 3. air intake system 13. control system 4. exhaust system 14. engine mounting system 5. lubrication system 15. camshaft and timing gear mechanism 6. starting and electrical system 16. piston, connecting rod , and cylinder 7. engine cover system mechanism ( the valve cover , for example ) 17. valve operating mechanism 8. emission control system 18. cylinder head mechanism 9. fastening system ( including valves , seats , springs , and retainers ) ( head bolts and other fasteners ) 19. cylinder block and crankshaft mechanism 10. sealing system 20. flywheel mechanism ( consisting of gaskets , O- rings , and lip-type seals ) 87

86. COMBUSTION CHAMBERS The combustion chamber configuration constitutes an important difference between gasoline and diesel engines . Gasoline engines have the chamber below the cover as shown in Figure , while most diesel engines have the chamber above the top of the piston. 88 Gasoline Engine Diesel Engine

87. DIESEL ENGINE OPERATION WHEN STARTING When you start a diesel , the engine turns and each cylinder fires in succession . During this process the engine must overcome the increasing power demand from parasitic loads , especially when the engine is cold . When a 12-volt starter motor begins cranking a large cold diesel engine, voltage at the starter can drop from 13.8 volts to only 10. Amperage does the opposite , going from zero to well over 1,500 amps in an instant . The sudden , strong electromagnetic fi eld around the starter cables may make them twitch or seem to crawl . Add parasitic loads into the equation and you can see why a cold start can sometimes be troublesome . The following are examples of parasitic loads during engine start- up . 89

88. DIESEL ENGINE OPERATION WHEN STARTING Power is needed for ;  1. overcoming inertia ( resistance to motion ) and turning the heavy flywheel and related components ; 2. turning the fuel transfer pump ; 3. the fuel injection equipment ( or ignition system ); 4. the engine oil pump ; 5. the engine coolant pump ; 6. the alternator ; 7. moving the column of cold air in the exhaust pipes and muffler ; 8. moving the pistons in cylinders that are not yet firing , along with their valve mechanisms . Another big energy draw includes starting an engine with a power-take-off engaged . This will greatly increase the load on the starter motor. (A power-take-off , or PTO, usually powers a hydraulic pump that drives a pot hauler , rigging hoist , etc ., on a workboat .) 90

89. DIESEL ENGINE OPERATION WHEN STARTING DIESEL FUEL INJECTION While the piston is approaching top- dead center on the compression stroke , the fuel injection system quickly builds high pressure to inject fuel into the cylinders . The fuel bursts into each cylinder and ignites in the hot, freshly compressed air in the cylinder . The heated air results from compression . LUBRICATION Prior to start- up , when the engine was turned off the night before , the lubricating oil slowly receded from between many of the components that depend so much on it. As the engine begins to turn , the oil pump quickly lifts a column of oil from the oil pan and forces all the air from the lubrication system . With the air gone , the vital lubricating oil flows in and around and through the engine, within seconds of starting . Crankshaft main bearings have four thousandths (0.004) of an inch oil clearance , then the combination of oil pressure and the rotation of the crankshaft will lift the crankshaft . This weight can be several hundred pounds . On larger engines this weight can exceed one thousand pounds . 91

90. ENGİNE RATİNGS 1. Newer engines are better at operating under light loads than older ones because of improved designs and materials . Another reason is that increasingly stringent emission standards are helping to ensure that all engines do a better job of burning fuel in the cylinder , and not in the exhaust manifold , even during light loading conditions . 2. Four-stroke engines handle light loads better than two-stroke engines because there is more time for the fuel to burn before the exhaust stroke . 3. Four-stroke engines with cast-iron pistons do better under light loads than those with aluminum pistons . At lower cylinder temperatures , the cast-iron piston- to - cylinder-wall clearance is less than it would be with aluminum pistons . 4. Direct fuel-injected engines do better under light loads than precombustion-chamber engines because the injection pressure is much greater and the fuel is more finely atomized . 92

91. ENGİNE RATİNGS 5. Air-cooled engines do better than watercooled engines under light loads because the cylinder temperature of an air-cooled engine tends to be 10 to 15 percent greater . 6. Electronically controlled engines perform better under light loads than mechanically governed engines because they inject fuel at higher pressures . The electronic engine’s control system quickly cuts back the amount of fuel injected as the load tapers off . 7. Square-cut piston compression rings often work better for lightly loaded engines than the tapered keystone-style rings . The reason for this is that square-cut rings are not as dependent on cylinder pressure to force the rings against the cylinder wall during light loads . 8. Three-ring pistons seal better than two ring pistons when an engine is under light load simply because they seal compression more efficiently . Two -ring engines are now quite rare . 93

92. ENGİNE RATİNGS 9. Naturally aspirated engines generally work better for light loads than turbocharged engines because their compression ratios are one or two points higher than a turbocharged engine. 10. Small- bore engines will work better than large-bore engines because it is easier to control piston ring leakage in a small cylinder . If we add all of the above together , we can come up with the ideal marine diesel engine for handling significant periods of operation under light loads . The engine would be technologically advanced , air-cooled , electronically controlled , four-stroke , direct-injected , naturally aspirated , and it would have cast-iron three -ring pistons and square-cut compression rings ! 94

93. FUEL QUALITY If you regularly buy your fuel from a single supplier , it makes sense to verify its quality . Consider sending a sample of the fuel to a lab and ask for a test to determine the cetane number . Some fuel suppliers have this information available for each shipment they receive . All engine manufacturers publish fuel specifications for their engines , and the fuel must conform to these specifications to ensure long engine life. Cleaning and water removal from diesel fuel can be done with a centrifuge or with fuel-water separators . While a centrifuge is expensive and requires constant maintenance , it is the method of choice for cleaning fuel . 95

94. MARINE ENGINE ENERGY EFFICIENCY For the foreseeable future , diesel engines will remain significantly more efficient ( Fig .) than gasoline engines . To save fuel after starting a cold diesel engine, idle it long enough to get good oil pressure and then get the boat moving with low rpm , light throttle , and light load until the engine is up to temperature . Never use full power until the engine is all the way up to operating temperature . 96

95. MARINE ENGINE ENERGY EFFICIENCY These additional items will also increase fuel efficiency: 1. Remove barnacles and keep the bottom of the boat painted. 2. When possible, reduce wind resistance. 3. Use the maximum allowable pitch and prop diameter that will allow the engine to get up to its rated full-load speed. 4. Be sure the exhaust system is unrestricted. 5. Engines are more efficient with plenty of cold air coming into the engine room. 6. Precisely tune your engine. 7. Use the lightest allowable weight of lube oil, or, better yet, use synthetic oil. 8. Use the smallest allowable generator set for house power; try to size it to operate at over 85 percent of its rated capacity. 9. Wherever possible, use 3-phase motors for the best electrical efficiency instead of single-phase motors. 10. For larger boats, if light loading is not a problem, use waste heat from the engine water jackets to warm the vessel, rather than electric heaters. 11. A little-known cause of excess fuel consumption is poor tracking while the vessel is under way, which results from poorly designed rudders and/or faulty autopilot adjustment. 97

96. MARINE ENGINE COOLING SYSTEMS The cooling system on your boat’s engine is critical. If it malfunctions, the engine will overheat, potentially causing severe damage. The term “heat exchanger” is a good example. On a boat, an engine’s oil cooler, aftercooler, intercooler, keel cooler, and freshwater (heat exchanger) cooler are all heat exchangers of one sort or another because they remove excess heat from the engine and direct it elsewhere. Figure shows how a basic marine heat exchanger works. 98 Heat exchanger construction and action.

97. MARINE ENGINE COOLING SYSTEMS FRESHWATER COOLING Raw water is water from the sea pumped into the boat with a raw-water pump, also called a seawater pump. The raw water passes through a strainer and an intake hose and circulates through a heat exchanger before it is pumped overboard, often through a water-cooled exhaust system where it mixes with exhaust gas. The raw water side of the system removes heat from the fresh water. The heat exchanger is a vital component in a freshwater cooling system. It facilitates the ability of raw water to remove heat from the coolant circulating inside the engine. Heat exchangers are usually made of corrosion - resistant copper-nickel alloy rather than straight copper tubing. 99

98. MARINE ENGINE COOLING SYSTEMS AFTERCOOLERS High-performance turbocharged diesel engines require additional cooling of the intake air. This is done with aftercoolers, which are also known as intercoolers. Figures show the air and raw-water flow through a heat-exchanger aftercooler. Aftercooling improves volumetric efficiency by cooling the air that is going into the cylinders—thus making it denser—and it is a good and necessary practice. 100

99. MARINE ENGINE COOLING SYSTEMS ENGINE COOLING COMPONENTS Every engine cooling system has key components such as pumps, thermostats, and hoses, to name just a few. Cooling System Hoses Coolant hoses, though pretty basic in function, are nevertheless vital parts of the cooling system. They must be protected from oil. Oil Coolers The engine oil cooler (Fig) is another form of heat exchanger within the cooling system. It is designed to take excess heat from the engine oil and dispose of it by transferring the heat to the engine coolant. 101

100. MARINE ENGINE COOLING SYSTEMS Thermostats When the engine is cold, the thermostat closes to recirculate coolant inside the engine. When the coolant reaches the thermostat’s rated temperature, the thermostat opens to send coolant out to the cooling loop. Thermostats are temperature-controlled coolant flow valves, and their job is to keep the coolant in the ideal temperature range as determined by the engine manufacturer. As the coolant nears its ideal temperature, the thermostat begins to open gradually, thereby helping avoid abrupt changes of temperature in the engine coolant. Abrupt changes in coolant temperature stress the engine castings. Of course, a thermostat that opens late or not at all will cause engine overheating. Thermostats are easy to test. Heat some water in a saucepan and place a meat thermometer in it. Simply watch to see when the thermostat opens and note the temperature when it does. Each thermostat has a temperature rating stamped on it, in degrees Fahrenheit or Celsius. If the thermostat doesn’t begin opening at its rated temperature, then it’s time to replace it. 102

101. MARINE ENGINE COOLING SYSTEMS THE EXPANSION TANK As coolant warms, it expands. For example, a cooling system holding 100 gallons of a water and antifreeze mixture will expand roughly 5 percent, or 5 gallons, between cold and hot extremes. In older boats, the cooling systems, if not properly serviced, will acquire a buildup of rust and precipitated dissolved solids (minerals). Some of this contamination will find its way into the cylinder block and settle around the cylinders. This buildup will eventually reduce keel cooler heat transfer and result in far more expansion of the coolant than will occur in an efficient cooling system. For this reason, ineffi cient cooling systems run higher coolant temperatures and will need larger expansion tanks. It is important to change coolant periodically as suggested by the engine manufacturer and to add distilled water rather than tap water. Using distilled water will keep the mineral content low in the coolant and reduce the likelihood of problems developing over time. It is vital to have a pressure cap on the cooling system. The pressurized system not only raises the boiling point of the coolant, but it also prevents the coolant from evaporating through the opening on the expansion tank and precipitating minerals. 103

102. MARINE ENGINE COOLING SYSTEMS Severe Engine Overheating If you see such a temperature spike (it can reach well above 210°F) on the temperature gauge, or if your engine suddenly stops, begin assessing how much damage has been done. If the engine has locked up while it was running, you know that the pistons have expanded due to heat and lodged in the bores. Excessive heat in the engine room and darkened paint on the outside of the engine are other indications of severe overheating. Check coolant and oil levels , and if you find both are normal, your engine may not have been damaged. However, you must track down what caused the overheating, be it a faulty raw-water or coolant pump , an obstruction in the raw - water intake line, or some other cause . Often, after an engine has cooled down after overheating, it will start and run, sometimes surprisingly well. In a case like this, cut open the oil filter and check the oil filter to learn if aluminum piston material is present in the lubricating oil. If the oil filter has aluminum in it, the piston damage is serious . The engine may be equipped with cast-iron pistons, which will produce darker (magnetic) iron particles. To further check the engine, pull a clean magnet through the filter media to check for the presence of iron from the cylinder walls or pistons, if the engine is equipped with iron pistons. The second problem that can occur after severe overheating is that the cylinder liner seals, if the engine is so equipped, can begin to leak coolant into the crankcase . If this has happened, the coolant and water mixture will go to the bottom of the oil pan. If the leak is small , the engine may have to be left shut off for an hour or so before coolant will accumulate in the pan. When water is present, simply loosening the oil pan drain plug will allow water to leak out first, making it easy to spot. When the engine is severely overheated, water-cooled exhaust manifolds, cylinder heads, and even the cylinder block can crack, causing coolant leaks into the oil pan. 104

103. BELTS AND HOSES Belts affixed to raw-water pumps, alternators, and coolant pumps all spin and transfer power to these components. From the viewpoint of manufacturers and boat - builders, drive belts are attractive for their simplicity, low cost, and convenience. Engine designers know that it will cost more to build an engine with a gear - driven coolant pump than one that is belt - driven. A disadvantage of the belt-driven pump, though, is that it will need the belts changed periodically. Hoses are another important part of a vast array of boat systems. Hoses, or lines, carry fuel, oil, coolant, raw water, potable water, propane gas, engine exhaust, and sewage. There are many types, each with its specific application. 105 Water Pump a nd Alternator Belts Raw-water, coolant, and alternator belts live in the engine room, where heat is a concern. High heat greatly reduces belt life. Too much or too little belt tension is another area to watch. overtightened belts will ruin water pump and alternator bearings.

104. BELTS AND HOSES Fuel Hoses and A i r in The Fuel The presence of air in the fuel reduces engine power and can cause hard starting. To eliminate the air, start working backward from the engine and tighten all fittings. If needed, reseal them with a sparing application of pipe sealant. Tighten the stem packing on all valves in the system. These valve stem packings can be a source of air entering the fuel system too. Watch for collapsed or damaged fuel hoses as well. Transmission Hoses Beware of a suction leak that allows the transmission oil pump to draw air with the oil. Aerated oil won’t provide proper lubrication. Suction leaks occur when the suction hose to the pump gets hard (difficult to bend). When this happens, replace it. Wet Exhaust System Hoses The exhaust pipe for horizontally positioned wet exhaust systems is usually made of fiberglass. Periodically check the inside of the wet exhaust elbow where the exhaust hose is attached for signs of coking (carbon). Coking occurs on some engines because the exhaust gases get cold so quickly that the hydrocarbon residue in the gases can solidify and build up inside the elbow. 106

105. BELTS AND HOSES COOLANT HOSES If your conventional coolant hoses (the black ones) seem to age, dry out, and fail prematurely, consider upgrading them to silicone hoses. silicone hoses don’t harden over time. In the long run you’ll save money, and don’t forget the safety implications if a coolant hose bursts when the boat is in a close-quarters maneuver or near rocks or other hazards. Heat and the effects of galvanic corrosion, the result of electrochemical action, cause many hose failures. Consider this interesting scenario: The pump inlet pipe becomes an anode, the hose becomes a cathode, and the coolant circulating inside the hose becomes an electrolyte because of higher-than-normal acidity. What you have is a form of battery, or, more properly termed, a galvanic cell generating low voltage that will shorten the life of the hose. 107

106. WATER IN THE FUEL OR LUBE OIL Water in diesel fuel will create havoc and water in oil degrades its lubrication ability. WATER IN THE FUEL Whether you have a gasoline or a diesel engine, the most common type of fuel contamination is fresh water. It can get into fuel through condensation in the fuel tank or rain entering tank vents and the fuel fill. If there is a low drain point in the tank, water must be drained from there. WATER IN THE ENGINE OIL When water leaks into the engine crankcase, it migrates to the bottom of the oil pan because it is heavier than the engine’s lube oil. It will stay on the bottom until the engine is started. When the engine is running, water is pulled from the bottom of the pan into the engine oil pump. From there it is sent through out the engine lubricating oil system. 108

107. WATER IN THE FUEL OR LUBE OIL WATER IN THE ENGINE OIL Unless water is removed from the oil , the oil and water emulsify into an oily black substance . at is worse than water alone mixing with the oil , because the resulting sludge ( Fig . 1) is so thick it plugs the lube oil passages in the engine on both the suction and pressure side of the oil pump ( Fig . 2). Plugged oil passages result in a loss of lubricating oil to the entire engine. This condition is first revealed at the crankshaft ( Fig . 3). Some engine manufacturers suggest flushing the engine with a special compound to remove the coolant residue , or completely dismantling the engine for piece-by-piece cleaning . Others recommend changing the oil twice in a short period of time and then sampling the oil . 109 Fig . 1 Fig . 2 Fig . 3

108. ENGINE TROUBLESHOOTING ENGINE MISSES Probable causes: • Air in the fuel • Water in the fuel • Faulty valve seat • Faulty injector • Faulty injection pump 110

109. ENGINE TROUBLESHOOTING ENGINE KNOCKS Probable causes : • Spun connecting rod bearing • Wrong fuel injection timing • Injector tip, glow-plug end , valve head , or other object in the cylinder intake , or exhaust valve stuck open and piston striking it • Severely worn engine bearings • Extreme crankshaft end play • Extreme clearance between cylinder wall and piston 111

110. ENGINE TROUBLESHOOTING ENGINE LOCKED UP, OR CRANKSHAFT WILL TURN JUST A LITTLE Probable causes: • Hydraulic lock with water, or fuel on top of a piston • Object on top of a piston • Piston rings and cylinder walls severely rusted due to water in the cylinder ( see Fig.) 112

111. ENGINE TROUBLESHOOTING ENGINE LOW ON POWER Probable causes: • Air filter plugged with dust and soot • Collapsed silencer or exhaust pipe • Wrong fuel in engine • Air in the fuel • Water in the fuel • Plugged fuel filter or restricted fuel lines on the suction side, pressure side, or return side of fuel system • Faulty fuel injection timing, injection pump, or injector, or faulty adjustment of injection pump or injector • Faulty turbocharger • Low compression due to cylinder damage • Valve clearance too much or too little, adjustment is set too loose or too tight 113

112. ENGINE TROUBLESHOOTING ENGINE STARTS HARD Probable causes: • Low battery charge causes slow cranking speed • Poor ground between engine and battery • Low or no fuel , wrong fuel type , air in fuel , or fuel filter plugged • Injection pump faulty or water damaged • Fuel injection timing wrong , low injection pump pressure , or poor atomizing of fuel by injectors • Low compression due to piston ring and cylinder wear • Exhaust pipe covered or blocked • Injection pump shutdown linkage stuck in the off position • Valve clearance setting too tight or too loose 114

113. ENGINE TROUBLESHOOTING EXCESSIVE BLACK EXHAUST Probable causes: • Plugged air filter • Excessive fuel delivery by pump or injectors • Insufficient atomization of fuel by the injector • Engine overloaded and lugging • Exhaust system restricted due to a collapsed muffler, or pipes with too small a diameter or too many tight bends 115

114. ENGINE TROUBLESHOOTING EXCESSIVE BLUE EXHAUST Probable causes: • Piston rings and cylinders extremely worn • Extremely worn valve guides and seals • Faulty oil seals in turbocharger • Engine overfilled with oil • Engine burns oil 116

115. ENGINE TROUBLESHOOTING EXCESSIVE WHITE EXHAUST Probable causes: • Low compression • Late injection timing • Water in the fuel or poor fuel quality 117

116. ENGINE TROUBLESHOOTING COOLANT TEMPERATURE TOO HIGH, LOW COOLANT FLOW Probable causes: • Coolant pump not turning , loose water pump belt if so equipped • Pump impeller slipping on shaft , broken , or reduced in size by corrosion COOLANT TEMPERATURE TOO HIGH, LOW COOLANT LEVEL Probable causes: • Thermostat faulty and not opening • Heat exchanger core plugged , or water inlet plugged 118

117. ENGINE TROUBLESHOOTING ENGINE OVERHEATING, YET COOLANT TEMPERATURE READS NORMAL OR LOW Probable causes: • Faulty gauge • Cooling system has large amount of air in it 119

118. ENGINE TROUBLESHOOTING LOW OIL PRESSURE Probable causes: • Low oil level or no oil in crankcase • Wrong viscosity of oil or oil diluted with fuel • Oil pump pressure relief valve stuck open • Crankshaft bearings extremely worn • Faulty gauge gives wrong reading when oil pressure is actually OK 120

119. ENGINE TROUBLESHOOTING HIGH OIL CONSUMPTION Probable causes : • Worn cylinder , pistons , and rings • Faulty turbocharger oil seals • Worn valve guides and valve stem seals • Incorrect lubricating oil • Plugged oil drain-back holes in cylinder head causing valve guide oil leakage 121

120. ENGINE TROUBLESHOOTING INSUFFICIENT POWER Fuel Supply Low fuel level and water in fuel: If there is no fuel gauge, dip the tank with a clean dowel or broom stick that will reach the bottom. It’s always good to dab the end of the dowel or broom handle with paste designed to change color if water is present in the fuel at the bottom of the tank. The paste is available at most fuel docks. If there is water in the tank, it must be removed. Fuel filters : The next check involves the fuel filters. If they are clogged , reduced power can result. Change the filters. Fuel line sizing: If the boat has been recently repowered with more powerful engines , take a careful look at the fuel lines. If they weren’t replaced when the new engines were installed, they may not have sufficient inner diameters to carry enough fuel. Poor fuel flow will make an engine appear to have less power than it should. 122

121. ENGINE TROUBLESHOOTING INSUFFICIENT POWER Wrong fuel type: Boats with gasoline engines have been mistakenly filled with diesel fuel. While the engine won’t run with diesel fuel in the tank, it doesn’t usually harm the engine. Replacing all the diesel fuel with gasoline is time-consuming, but it is a simple fix. fuel injection control levers: The control lever on the engine must move to full fuel when the engine speed control in the wheelhouse is pulled into the full speed position. If it doesn’t, the throttle control must be repaired or adjusted. Mufflers and air filters : A collapsed muffler (silencer) will reduce engine power by restricting airflow through the engine, which will result in excessive back-pressure. Check the back-pressure on the engine exhaust system every two years. Adequate airflow into and through the engine must not be hindered in any way. Many engines have a filter restriction gauge on the intake air system that shows red when the air filter should be serviced; air filters get loaded with dust and grime. Always check the condition of your air filter to avoid potential low power problems. 123

122. ENGINE TROUBLESHOOTING INSUFFICIENT POWER Line in the propeller: line wrapped around the propeller or propeller shaft will make it appear as though the enginee has a low power problem. B ecause it will take much more effort to turn the shaft . Checking the cylinders : There are some indirect ways to learn what is happening in the heart of the engine. Auto repair shops use engine analyzers to check gasoline cylinder condition by turning off the spark to one cylinder at a time and then measuring the amount the engine speed drops. Engine speed drops the most when cylinders that are carrying their share of the load are shorted out. However, when weak cylinders are shorted out the engine speed changes very little. 124

123. ENGINE TROUBLESHOOTING TROUBLESHOOTING HARD STARTS—DIESEL AND GAS ENGINES T he first thing to do if faced with a hard start regardless of what type of engine you have is to check the fuel level and fuel filters. CRANKSHAFT WON’T TURN WHEN STARTER ENGAGED , NO SOUND OF STARTER MOTOR TRYING TO WORK Probable causes: • Faulty or discharged battery, • Corroded battery terminals, corroded or partially cut cables , • Alternator output low or nonexistent, belt slipping , excessively worn pulley • Faulty starter switch, low voltage to switch • Bad starter solenoid 125

124. ENGINE TROUBLESHOOTING CAN HEAR THE STARTER TRYING TO TURN CRANKSHAFT , BUT ENGINE WON’T TURN FAST ENOUGH TO START Probable cause: Possible low voltage Suggested action: See previous actions related to charging ENGINE TURNS BUT WILL NOT START Probable causes: • Engine not getting fuel • Low compression in cylinders • Fuel injection timing out of specification 126

125. 127 Vapors Compression Refrigeration Two-phase liquid-vapor mixture Almost all marine refrigeration and air - conditioning systems operate on the vapor - compression cycle . The vapor - compression cycle consists of the following processes : (l) expansion , (2) vaporization , (3) compression , and (4) condensation . Process 4-1 : two-phase liquid-vapor mixture of refrigerant is evaporated through heat transfer from the refrigerated space. Process 1-2 : vapor refrigerant is compressed to a relatively high temperature and pressure requiring work input. Process 2-3 : vapor refrigerant condenses to liquid through heat transfer to the cooler surroundings. Process 3-4 : liquid refrigerant expands to the evaporator pressure .

126. MARINE REFRIGERATION AND AIR CONDITION SYSTEM 128

127. MARINE REFRIGERATION AND AIR CONDITION SYSTEM 129

128. 130 As the temperature drops, more energy is required to run a machine, while the operating power of the battery decreases. A battery should have sufficient capacity to cope with the worst expected situation.

129. 131 Battery capacity as a function of the rate of discharge: 100 Ah battery, (20-hour) rating

130. 132

131. 133 Series connection. The Ah capacity is unchanged from a single battery’s capacity, but output voltage is doubled. Twelve-volt batteries should never be connected in series on a 12-volt electrical system—the resulting high voltage will damage equipment. When in series, the total amp-hour capacity of the two batteries together remains the same as the amp-hour rating of either one, but the output voltage is doubled.

132. 134 Parallel connection. Output voltage remains the same as that of the individual batteries, but Ah capacity is doubled. Paralleling batteries leaves the system voltage unchanged, but doubles the amp-hour capacity. Connecting two 200 Ah, 12-volt batteries in parallel produces only 12 volts, but has a 400 Ah capacity.