Patent Publication Number: US-10322785-B2

Title: Outboard motor

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority to Japanese Patent Application No. 2017-041617 filed on Mar. 6, 2017. The entire contents of this application are hereby incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to outboard motors. 
     2. Description of the Related Art 
     There is a type of outboard motor including an oil cooler for cooling oil that circulates inside an engine. For example, Japan Laid-open Patent Application Publication No. 2000-120420 describes an outboard motor in which an oil cooler is disposed forward of a crankshaft of an engine. An oil cooler cooling pipe is connected to a lateral surface of the oil cooler, and is disposed to pass through a lateral side of the engine. Additionally, a water discharge pipe is connected to the front surface of the oil cooler. Cooling water is supplied to the oil cooler through the oil cooler cooling pipe, and is discharged from the oil cooler through the water discharge pipe. 
     In the above described outboard motor, the water discharge pipe is connected to the front surface of the oil cooler at a position above the bottom surface of the oil cooler, and horizontally extends from the oil cooler. Therefore, when the outboard motor is tilted up after deactivation of the engine, the performance of water discharge from the oil cooler degrades, such that the cooling water is likely to remain inside the oil cooler. This may result in freezing of the cooling water inside the oil cooler. When the engine is restarted under this condition, the flow rate of the cooling water reduces and thus cooling efficiency degrades. Thus, there has been room for improvement regarding a cooling system in the well-known outboard motor. 
     SUMMARY OF THE INVENTION 
     Preferred embodiments of the present invention provide outboard motors in which performance of water discharge from an oil cooler is enhanced when an engine is deactivated and the outboard motor is tilted up. 
     An outboard motor according to a preferred embodiment of the present invention includes an engine, a drive shaft, a propeller shaft, an oil cooler, an engine cooling water passage, an oil cooling water passage, and a water discharge passage. The engine includes a crankshaft. The drive shaft is connected to the crankshaft, and extends downwardly from the engine. The propeller shaft is connected to the drive shaft, and extends in a direction intersecting with the drive shaft. The oil cooler is disposed forward of the crankshaft. The engine cooling water passage is disposed inside the engine. The oil cooling water passage is connected to the oil cooler and branches from the engine cooling water passage. The water discharge passage is connected to the oil cooler. The water discharge passage is disposed lower than the oil cooler and forward of a center axis of the crankshaft. 
     In the outboard motors according to the present preferred embodiment, the water discharge passage is disposed lower than the oil cooler and forward of the center axis of the crankshaft. With this structure, water discharge from the oil cooler is enhanced when the engine is deactivated and the outboard motor is tilted up. 
     The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of an outboard motor according to a preferred embodiment of the present invention. 
         FIG. 2  is a side view of a schematic configuration of an engine. 
         FIG. 3  is a block diagram showing a structure of a cooling water passage in the outboard motor. 
         FIG. 4  is a perspective view of the cooling water passage in the outboard motor. 
         FIG. 5  is a side view of the cooling water passage in the outboard motor. 
         FIG. 6  is a perspective view of a portion of a third oil pan water passage and a second guide water passage. 
         FIG. 7  is a perspective view of a portion of the third oil pan water passage. 
         FIG. 8  is a diagram showing the outboard motor in a tilted-up position. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred embodiments of the present invention will be hereinafter explained with reference to drawings.  FIG. 1  is a side view of an outboard motor  1  according to a preferred embodiment of the present invention. The outboard motor  1  includes an engine  2 , a drive shaft  3 , a propeller shaft  4 , and a shift mechanism  5 . 
     The engine  2  generates a thrust that propels a watercraft. The engine  2  includes a crankshaft  6 . The crankshaft  6  extends in the vertical direction. The drive shaft  3  is connected to the crankshaft  6 . The drive shaft  3  extends in the vertical direction. The drive shaft  3  extends downwardly from the engine  2 . 
     The propeller shaft  4  extends in the back-and-forth direction. The propeller shaft  4  is connected to the drive shaft  3  through the shift mechanism  5 . A propeller  7  is connected to the propeller shaft  4 . The shift mechanism  5  switches a rotational direction of power to be transmitted from the drive shaft  3  to the propeller shaft  4 . The shift mechanism  5  includes, for instance, a plurality of gears and a clutch that changes meshing of the gears. 
     The outboard motor  1  includes a cowl  8 , an upper housing  9 , and a lower housing  10 . The cowl  8  accommodates the engine  2 . The upper housing  9  is disposed below the cowl  8 . The lower housing  10  is disposed below the upper housing  9 . The upper housing  9  and the lower housing  10  accommodate the drive shaft  3 . The lower housing  10  accommodates the propeller shaft  4 . 
     The outboard motor  1  includes a bracket  11 . The outboard motor  1  is attached to the watercraft through the bracket  11 . The bracket  11  includes a trim and tilt shaft  12 . The trim and tilt shaft  12  extends in the right-and-left direction. The bracket  11  supports the outboard motor  1  such that the outboard motor  1  is rotatable about the trim and tilt shaft  12 . 
       FIG. 2  is a side view of a schematic configuration of the engine  2 . As shown in  FIG. 2 , the engine  2  includes a crankcase  13 , a cylinder body  14 , and a cylinder head  15 . The cylinder body  14  is disposed behind the crankcase  13 . The crankcase  13  and the cylinder body  14  accommodate the crankshaft  6 . The cylinder head  15  is disposed behind the cylinder body  14 . 
     The outboard motor  1  includes an exhaust manifold  16  and an exhaust pipe  17 . The exhaust manifold  16  is connected to the cylinder head  15 . The engine  2  is preferably a multi-cylinder engine, and the exhaust manifold  16  aggregates exhaust gas from a plurality of cylinders of the cylinder head  15 . It should be noted that the engine  2  may be a single-cylinder engine. In this case, the exhaust manifold  16  may not be provided. 
     The exhaust pipe  17  is connected to the exhaust manifold  16 . The exhaust pipe  17  is disposed behind the cylinder head  15 . The exhaust pipe  17  extends downward. 
     The outboard motor  1  includes a support  18  and a muffler  23 . The support  18  is disposed below the engine  2  and supports the engine  2 . The support  18  includes an exhaust guide  21  and an oil pan  22 . The engine  2  is disposed on the exhaust guide  21 . The exhaust pipe  17  is connected to the exhaust guide  21 . The oil pan  22  is disposed below the exhaust guide  21 . The muffler  23  is disposed below the oil pan  22 . An exhaust passage  24  is disposed in the exhaust guide  21 , the oil pan  22 , and the muffler  23 . The exhaust passage  24  is connected to the exhaust pipe  17 . 
     The outboard motor  1  includes a first oil cooler  25 . The first oil cooler  25  is disposed in front of the engine  2 . The first oil cooler  25  is attached to the front surface of the crankcase  13 . The first oil cooler  25  is disposed forward of the crankshaft  6 . 
     An electric component  26  is attached to the first oil cooler  25 . The electric component  26  is, for instance, a rectifier/regulator. It should be noted that an electric component other than the rectifier/regulator may be attached to the first oil cooler  25 . The first oil cooler  25  cools lubricating oil that circulates inside the engine  2 . Additionally, the first oil cooler  25  cools the electric component  26 . 
     The first oil cooler  25  includes a first cooler portion  27 , a second cooler portion  28 , and a third cooler portion  29 . The first cooler portion  27 , the third cooler portion  29 , and the second cooler portion  28  are aligned in the up-and-down direction. The second cooler portion  28  and the third cooler portion  29  are disposed above the first cooler portion  27 . The third cooler portion  29  is disposed between the first cooler portion  27  and the second cooler portion  28 . In a front view, the area of the third cooler portion  29  is the largest among the areas of the first to third cooler portions  27  to  29 . The electric component  26  is connected to the third cooler portion  29 . 
       FIG. 3  is a block diagram showing a structure of a cooling water passage in the outboard motor  1 . As shown in  FIG. 3 , the cooling water passage in the outboard motor  1  includes an inlet  31 , a water pump  32 , an engine cooling water passage  33 , an oil cooling water passage  34 , and an outlet  35 . 
     The inlet  31  is disposed in the lower housing  10 . Water is taken into the cooling water passage from the outside of the outboard motor  1  through the inlet  31 . The water pump  32  sucks the water through the inlet  31  and feeds the water to the engine cooling water passage  33  and the oil cooling water passage  34 . The engine cooling water passage  33  is disposed inside the engine  2 . The oil cooling water passage  34  is connected to the first oil cooler  25 . The oil cooling water passage  34  branches from the engine cooling water passage  33 . 
       FIG. 4  is a perspective view of the cooling water passage in the outboard motor  1 .  FIG. 5  is a side view of the cooling water passage in the outboard motor  1 . It should be noted that in  FIG. 5 , the dashed dotted line C 1  indicates the center axis of the crankshaft  6 . Additionally in  FIG. 5 , a dashed two-dotted line indicates the approximate positions of the crankcase  13 , the cylinder body  14 , the cylinder head  15 , the exhaust guide  21 , the oil pan  22 , and the muffler  23 . 
     As shown in  FIGS. 4 and 5 , the cooling water passage includes a muffler water passage  47 . The muffler water passage  47  is disposed inside the muffler  23 . As shown in  FIG. 3 , the muffler water passage  47  is connected to the inlet  31 . The muffler water passage  47  is connected to the engine cooling water passage  33  and the oil cooling water passage  34 . 
     The engine cooling water passage  33  includes a first oil pan water passage  48 , a first guide water passage  49 , and an exhaust pipe water passage  50 . The first oil pan water passage  48  is disposed inside the oil pan  22 . The first oil pan water passage  48  is connected to the muffler water passage  47 . The first guide water passage  49  is disposed inside the exhaust guide  21 . The first guide water passage  49  is connected to the first oil pan water passage  48 . The exhaust pipe water passage  50  is disposed inside the exhaust pipe  17 . The exhaust pipe water passage  50  is connected to the first guide water passage  49 . 
     A first engine water passage  36  includes a first manifold water passage  51 , a first cylinder head water passage  52 , a first cylinder body water passage  53 , and a first engine cooling pipe  54 . The first manifold water passage  51  is disposed inside the exhaust manifold  16 . The first cylinder head water passage  52  is disposed inside the cylinder head  15 . The first cylinder head water passage  52  is connected to the first manifold water passage  51 . The first cylinder body water passage  53  is disposed inside the cylinder body  14 . The first cylinder body water passage  53  is connected to the first cylinder head water passage  52 . A thermostat  45  is disposed downstream of the first cylinder body water passage  53 . 
     The first engine cooling pipe  54  is disposed outside the engine  2 . The first engine cooling pipe  54  is disposed inside the cowl  8 . The first engine cooling pipe  54  extends in the up-and-down direction. The engine cooling water passage  33  includes a second oil pan water passage  59 . The second oil pan water passage  59  is disposed inside the oil pan  22 . The first engine cooling pipe  54  connects the first cylinder head water passage  52  and the second oil pan water passage  59 . 
     A second engine water passage  37  includes a second manifold water passage  55 , a second cylinder head water passage  56 , a second cylinder body water passage  57 , and a second engine cooling pipe  58 . The second manifold water passage  55  is disposed inside the exhaust manifold  16 . The second cylinder head water passage  56  is disposed inside the cylinder head  15 . The second cylinder head water passage  56  is connected to the second manifold water passage  55 . The second cylinder body water passage  57  is disposed inside the cylinder body  14 . The second cylinder body water passage  57  is connected to the second cylinder head water passage  56 . A thermostat  46  is disposed downstream of the second cylinder body water passage  57 . 
     The second engine cooling pipe  58  is disposed outside the engine  2 . The second engine cooling pipe  58  is disposed inside the cowl  8 . The second engine cooling pipe  58  extends in the up-and-down direction. The second engine cooling pipe  58  connects the second cylinder head water passage  56  and the second oil pan water passage  59 . 
     Water taken through the inlet  31  flows to the exhaust pipe water passage  50  through the muffler water passage  47 , the first oil pan water passage  48 , and the first guide water passage  49 . The water flows upwardly in the muffler water passage  47 , the first oil pan water passage  48 , the first guide water passage  49 , and the exhaust pipe water passage  50 . 
     A portion of the water flows from the exhaust pipe water passage  50  to the second oil pan water passage  59  through the first manifold water passage  51 , the first cylinder head water passage  52 , the first cylinder body water passage  53 , and the first engine cooling pipe  54 . The water flows downwardly in the first engine cooling pipe  54 . 
     On the other hand, another portion of the water flows from the exhaust pipe water passage  50  to the second oil pan water passage  59  through the second manifold water passage  55 , the second cylinder head water passage  56 , the second cylinder body water passage  57 , and the second engine cooling pipe  58 . The water flows downwardly in the second engine cooling pipe  58 . The water merges in the second oil pan water passage  59  and is discharged through the outlet  35 . 
     The oil cooling water passage  34  has a smaller cross-section in the flow passage than the engine cooling water passage  33 . The oil cooling water passage  34  branches into a first oil water passage  64  and a second oil water passage  65 . 
     The first oil water passage  64  includes a first cooling water passage  66  and a second cooling water passage  67 . The first cooling water passage  66  is located upstream of the first oil cooler  25 . The first cooling water passage  66  extends from the oil pan  22 , passes through the exhaust guide  21  and the crankcase  13 , and is connected to the first oil cooler  25 . The second cooling water passage  67  is located downstream of the first oil cooler  25 . The second cooling water passage  67  connects the first oil cooler  25  and the engine cooling water passage  33 . 
     The first cooling water passage  66  includes a third oil pan water passage  63 , a second guide water passage  68 , and a case water passage  69 . The third oil pan water passage  63  is disposed inside the oil pan  22 . The second guide water passage  68  is disposed inside the exhaust guide  21 . The second guide water passage  68  is connected to the third oil pan water passage  63 . 
     The third oil pan water passage  63 , the second guide water passage  68 , and the case water passage  69  are disposed below the first oil cooler  25 . A portion of the third oil pan water passage  63  is located forward of a center axis C 1  of the crankshaft  6 . A portion of the second guide water passage  68  is located forward of the center axis C 1  of the crankshaft  6 . The case water passage  69  is located forward of the center axis C 1  of the crankshaft  6 . 
     The case water passage  69  is disposed inside the crankcase  13 . The case water passage  69  is connected to the second guide water passage  68 . As shown in  FIGS. 4 and 5 , the case water passage  69  includes a body water passage  71 , a first connecting water passage  72 , and a second connecting water passage  73 . The body water passage  71  is connected to the second guide water passage  68 . The body water passage  71  extends upwardly from the second guide water passage  68 . 
     The first connecting water passage  72  is connected to the body water passage  71 . The first connecting water passage  72  extends from the body water passage  71  in the right-and-left direction. The first connecting water passage  72  connects the body water passage  71  and the first cooler portion  27 . As shown in  FIG. 5 , the first cooler portion  27  includes a first connection port  74 . The first connecting water passage  72  is connected to the first connection port  74 . 
     The second connecting water passage  73  is connected to the body water passage  71 . The second connecting water passage  73  extends from the body water passage  71  in the right-and-left direction. The second connecting water passage  73  is located higher than the first connecting water passage  72 . The second connecting water passage  73  connects the body water passage  71  and the third cooler portion  29 . The third cooler portion  29  includes a third connection port  76 . The third connection port  76  is located higher than the first connection port  74 . The second connecting water passage  73  is connected to the third connection port  76 . 
     The first cooler portion  27  and the third cooler portion  29  are connected through a first coupling water passage  77 . The first coupling water passage  77  extends upwardly from the first cooler portion  27  toward the third cooler portion  29 . The third cooler portion  29  and the second cooler portion  28  are connected through a second coupling water passage  78 . The second coupling water passage  78  extends upwardly from the third cooler portion  29  toward the second cooler portion  28 . 
     The second cooling water passage  67  includes a first oil cooling pipe  79 . The first oil cooling pipe  79  is disposed outside the engine  2 . The first oil cooling pipe  79  is disposed inside the cowl  8 . The first oil cooling pipe  79  is connected to the first oil cooler  25 . The second cooler portion  28  includes a second connection port  75 . The second connection port  75  is located higher than the first connection port  74  and the third connection port  76 . The first oil cooling pipe  79  is connected to the second cooler portion  28 . 
     The first oil cooling pipe  79  extends sideways from the second cooler portion  28  and then bends backward. Additionally, the first oil cooling pipe  79  bends downward, and then extends downwards and through a lateral side of the engine  2 . The first oil cooling pipe  79  is connected to the first engine cooling pipe  54 . 
     The water taken in through the inlet  31  flows to the first oil cooler  25  through the muffler water passage  47 , the third oil pan water passage  63 , the second guide water passage  68 , and the case water passage  69 . The water flows upwardly in the muffler water passage  47 , the third oil pan water passage  63 , the second guide water passage  68 , and the case water passage  69 . 
     In the case water passage  69 , a portion of the water flows from the first connecting water passage  72  to the third cooler portion  29  through the first cooler portion  27  and the first coupling water passage  77 . In the case water passage  69 , another portion of the water flows from the second connecting water passage  73  to the third cooler portion  29 . The water merges in the third cooler portion  29  and flows to the first oil cooling pipe  79  through the second coupling water passage  78  and the second cooler portion  28 . The water flows upwardly in the first cooler portion  27 , the first coupling water passage  77 , the third cooler portion  29 , the second coupling water passage  78 , and the second cooler portion  28 . 
     As described above, the water, which has flowed through the first oil cooler  25 , flows from the first oil cooling pipe  79  to the first engine cooling pipe  54 , and is discharged through the outlet  35  together with the water that has cooled the engine  2  as described above. 
     The outboard motor  1  preferably includes a second oil cooler  30 . The second oil cooler  30  is disposed inside the cylinder body  14 . The second oil water passage  65  is connected to the first oil water passage  64 . The second oil water passage  65  is connected to the first oil water passage  64  in a downstream portion of the first oil cooler  25 . 
     The second oil water passage  65  includes a third guide water passage  83 , a third cylinder body water passage  84 , and a second oil cooling pipe  85 . The third guide water passage  83  is disposed inside the exhaust guide  21 . The third guide water passage  83  is connected to the third oil pan water passage  63 . The third guide water passage  83  extends upwardly from the third oil pan water passage  63 . 
     The third cylinder body water passage  84  is disposed inside the cylinder body  14 . The third cylinder body water passage  84  is connected to the third guide water passage  83 . The third cylinder body water passage  84  extends upwardly from the third guide water passage  83 . The third cylinder body water passage  84  is connected to a bottom portion of the second oil cooler  30 . 
     The second oil cooling pipe  85  is connected to a top portion of the second oil cooler  30 . The second oil cooling pipe  85  extends upwardly from the second oil cooler  30  and bends sideways. The second oil cooling pipe  85  is connected to the first oil cooling pipe  79 . 
     The water taken in through the inlet  31  flows to the second oil cooler  30  through the muffler water passage  47 , the third oil pan water passage  63 , and the third guide water passage  83 . The water flows upwardly in the muffler water passage  47 , the third oil pan water passage  63 , the third guide water passage  83 , and the second oil cooler  30 . 
     As described above, the water, which has flowed through the second oil cooler  30 , flows from the second oil cooling pipe  85  to the first engine cooling pipe  54  through the first oil cooling pipe  79 , and is discharged through the outlet  35  together with the water that has cooled the engine  2  as described above. 
     It should be noted that the cooling water passage includes a fourth guide water passage  61  and a fifth guide water passage  62 . The fourth guide water passage  61  and the fifth guide water passage  62  are disposed inside the exhaust guide  21 . The fourth guide water passage  61  is connected to the third oil pan water passage  63 . The fourth guide water passage  61  extends upwardly from the third oil pan water passage  63 . The fourth guide water passage  61  is connected to the first cylinder body water passage  53 . 
     The fifth guide water passage  62  is connected to the third oil pan water passage  63 . The fifth guide water passage  62  extends upwardly from the third oil pan water passage  63 . The fifth guide water passage  62  is connected to the second cylinder body water passage  57 . 
     Inside the oil pan  22 , the first, second and third oil pan water passages  48 ,  59  and  63  are preferably integral with the oil pan  22 . Inside the exhaust guide  21 , the first, second, third, fourth and fifth guide water passages  49 ,  68 ,  83 ,  61  and  62  are preferably integral with the exhaust guide  21 . Inside the crankcase  13 , the case water passage  69  is preferably integral with the crankcase  13 . 
     A fuel cooler  86  is connected to the case water passage  69 . The fuel cooler  86  is disposed on a fuel tank (not shown in the drawings). The fuel cooler  86  extends in the up-and-down direction. The fuel cooler  86  is connected to the first oil cooling pipe  79 . A portion of the water inside the case water passage  69  flows upwardly through the fuel cooler  86 . The portion of the water flows from the fuel cooler  86  to the first oil cooling pipe  79  and merges with the water that has flowed through the first oil cooler  25 . 
     The cooling water passage preferably includes a flushing water passage  87  and a drain water passage  88 . The flushing water passage  87  and the drain water passage  88  are connected to the first cooler portion  27 . When cleaning the cooling water passage, water is supplied to the flushing water passage  87 . The water supplied to the flushing water passage  87  flows through the cooling water passage in the outboard motor  1 , thus the cooling water passage is cleaned. After cleaning the cooling water passage, the water is discharged through the drain water passage  88 . 
       FIG. 6  is a perspective view of a portion of the third oil pan water passage  63  and the second guide water passage  68 .  FIG. 7  is a perspective view of a portion of the third oil pan water passage  63 . As shown in  FIG. 6 , the oil pan  22  and the exhaust guide  21  include a hole  89  into which the crankshaft  6  is inserted. The third oil pan water passage  63  and the second guide water passage  68  surround the hole  89 . 
     As shown in  FIG. 7 , the oil pan  22  includes a water discharge hole  91 . The water discharge hole  91  communicates with the third oil pan water passage  63 . The water discharge hole  91  extends downwardly through the interior of the oil pan  22 . The water discharge hole  91  communicates with the interior of the lower housing  10  through the interior of the upper housing  9 . 
     The opening area of the water discharge hole  91  is smaller than the cross-sectional flow area of the third oil pan water passage  63 . As shown in  FIG. 6 , the second guide water passage  68  includes a connecting water passage  92 . The connecting water passage  92  is connected to the case water passage  69 . The opening area of the water discharge hole  91  is smaller than the cross-sectional flow area of the connecting water passage  92 . 
     As shown in  FIG. 3 , the cooling water passage includes a water discharge passage  93 . The water discharge passage  93  includes the case water passage  69 , the second guide water passage  68 , the third oil pan water passage  63 , and the water discharge hole  91 . Therefore, the water discharge passage  93  includes a portion of the first cooling water passage  66 , in other words, the case water passage  69 , the second guide water passage  68 , and the third oil pan water passage  63 . Put differently, the water discharge passage  93  is connected to the first oil cooler  25  through the first cooling water passage  66 . A portion of the water discharge passage  93  is disposed lower than the first oil cooler  25  and forward of the center axis C 1  of the crankshaft  6 . 
     When deactivating the engine  2 , the water inside the first oil cooler  25  is discharged to the outside of the outboard motor  1  through the water discharge passage  93 . In detail, the water inside the first oil cooler  25  flows into the upper housing  9  through the case water passage  69 , the second guide water passage  68 , the third oil pan water passage  63 , and the water discharge hole  91 . The water inside the upper housing  9  flows through the interior of the lower housing  10  and is discharged therefrom to the outside. 
     Therefore, the case water passage  69 , the second guide water passage  68 , and the third oil pan water passage  63  define a portion of the first cooling water passage  66  when activating the engine  2 , but on the other hand, define a portion of the water discharge passage  93  when deactivating the engine  2 . 
       FIG. 8  shows the outboard motor  1  in a tilted-up position. In the outboard motor  1  according to the present preferred embodiment, the water discharge passage  93  is disposed lower than the first oil cooler  25  and forward of the center axis C 1  of the crankshaft  6 . Therefore, as shown in  FIG. 8 , even when the engine  2  is deactivated and the outboard motor  1  is in the tilted-up position, water discharge from the first oil cooler  25  is enhanced. 
     Preferred embodiments of the present invention have been explained above. However, the present invention is not limited to the above described preferred embodiments, and a variety of changes can be made without departing from the gist of the present invention. 
     The layout of the cooling water passage may be changed. The layout of the engine cooling water passage  33  may be changed. For example, the engine cooling water passage  33 , designed to pass through the exhaust pipe  17 , the exhaust manifold  16 , the cylinder head  15  and the cylinder body  14 , may pass therethrough in a different order. 
     The layout of the first oil water passage  64  may be changed. For example, the first oil water passage  64  may not be provided with any of the case water passage  69 , the second guide water passage  68 , and the third oil pan water passage  63 . The shapes of the case water passage  69 , the second guide water passage  68 , and the third oil pan water passage  63  may be changed. A portion of the first oil water passage  64  may include a pipe or a hose. 
     The layout of the second oil water passage  65  may be changed. A portion of the second oil water passage  65  may include a pipe or a hose. Alternatively, the second oil water passage  65  may not be provided. 
     The water discharge passage  93  may be provided independently from the first cooling water passage  66 . The water discharge passage  93  may not be provided with any of the case water passage  69 , the second guide water passage  68 , and the third oil pan water passage  63 . A portion of the water discharge passage  93  may include a pipe or a hose. 
     The water discharge hole  91  may be disposed in an element other than the oil pan  22 . For example, the water discharge hole  91  may be disposed in the exhaust guide  21 . The water discharge hole  91  may communicate with an element other than the interior of the lower housing  10 . For example, the water discharge hole  91  may be connected to the outlet  35  provided in the upper housing  9 . 
     The structure of the first oil cooler  25  may be changed. For example, any of the first, second and third cooler portions  27  to  29  may not be provided. The first, second and third cooler portions  27  to  29  may be integral with each other. The structure of the second oil cooler  30  may be changed. Alternatively, the second oil cooler  30  may not be provided. 
     While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.