Abstract:
Please make the following amendments to the abstract. Material to be inserted in replacement paragraphs or sections is in bold and underline, and material to be deleted is in and/or in if the deletion would be difficult to see. 
     Please replace abstract with the following rewritten abstract: A water muffler of a personal watercraft comprises: a muffler body; and an inlet pipe which is connected to the muffler body and guides an exhaust gas and cooling water to an inner space of the muffler body. The inlet pipe includes: a center pipe wall; an outer pipe wall provided to surround the center pipe wall; an exhaust passage which is provided inside the center pipe wall; and a water passage surrounded by the center pipe wall and the outer pipe. The center pipe wall has in a downstream end portion of the inlet pipe, a protruding portion protruding from the outer pipe wall in an axial direction of the inlet pipe, and an outlet of the water passage is located to be apart from an outlet of the exhaust passage in an axial direction of the inlet pipe.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    Field of the Invention 
         [0002]    The present invention relates to a water muffler incorporated into a personal watercraft. 
         [0003]    Description of Related Art 
         [0004]    In a personal watercraft, a water muffler is used as an exhaust gas silencer (see U.S. Pat. No. 7,326,093 B2). The water muffler includes an inlet pipe connected to an exhaust pipe extending from an engine. This inlet pipe has a double-walled structure including a center pipe wall, and an outer pipe wall formed to surround the center pipe wall. The inlet pipe is provided with an exhaust passage formed inside the center pipe wall, and a water passage surrounded by the center pipe wall and the outer pipe wall. The downstream end of the inlet pipe is formed with an outlet of the exhaust passage and an outlet of the water passage. The exhaust gas and cooling water flow into the interior of the water muffler through the outlet of the exhaust passage and the outlet of the water passage. 
         [0005]    Typically, an exhaust gas outlet and a water outlet are placed to be coplanar with each other. For this reason, the cooling water is highly likely to flow into the exhaust passage through the exhaust gas outlet located inward relative to and close to the water outlet. As a result, the cooling water may flow back toward the engine through the exhaust passage. 
       SUMMARY OF THE INVENTION 
       [0006]    An object of the present invention is to provide a water muffler which can make it difficult for cooling water to flow back through an exhaust passage. 
         [0007]    According to an aspect of the present invention, a water muffler of a personal watercraft comprises a muffler body having a tubular shape; and an inlet pipe which is connected to the muffler body and guides an exhaust gas and cooling water to an inner space of the muffler body, wherein the inlet pipe includes: a center pipe wall; an outer pipe wall provided to surround the center pipe wall; an exhaust passage which is provided inside the center pipe wall and through which the exhaust gas flows; and a water passage which is surrounded by an outer peripheral surface of the center pipe wall and an inner peripheral surface of the outer pipe wall, and through which cooling water flows, wherein the center pipe wall has in a downstream end portion of the inlet pipe, a protruding portion protruding from the outer pipe wall in an axial direction of the inlet pipe, and an outlet of the water passage is located to be apart from an outlet of the exhaust passage in the axial direction of the inlet pipe. 
         [0008]    In accordance with this configuration, since the outlet of the water passage is located to be apart from the outlet of the exhaust passage in the axial direction of the inlet pipe, the cooling water does not easily reach the outlet of the exhaust passage, after the cooling water has flowed through the water passage and into the inner space of the muffler body. Therefore, the cooling water does not easily flow back through the exhaust passage. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a side view of a personal watercraft according to an embodiment. 
           [0010]      FIG. 2  is a plan view of the personal watercraft. 
           [0011]      FIG. 3  is a schematic view showing an exhaust system. 
           [0012]      FIG. 4A  is a cross-sectional view showing a part of a muffler body and a part of an inlet pipe.  FIG. 4B  is a cross-sectional view of the inlet pipe which is taken along line B-B of  FIG. 4A .  FIG. 4C  is a cross-sectional view of the inlet pipe which is taken along line C-C of  FIG. 4A .  FIG. 4D  is a view taken in the direction of arrows along line D-D of  FIG. 4A  (a view showing the downstream end of the inlet pipe when viewed from a first chamber in an axial direction). 
           [0013]      FIG. 5  is a cross-sectional view taken along line V-V of  FIG. 4A . 
           [0014]      FIG. 6A  is a cross-sectional view of a right deck fin, in a region which is in the vicinity of a flange of an exhaust system, when viewed from the front.  FIG. 6B  is a cross-sectional view of the right deck fin, in a region which is in the vicinity of a swelling portion of the exhaust system, when viewed from the front. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0015]    Hereinafter, the embodiment will be described with reference to the drawings. The stated directions are from the perspective of a rider riding on a personal watercraft  1 . 
         [0016]    As shown in  FIGS. 1 and 2 , the personal watercraft  1  includes a body  2  including a hull  3  and a deck  4 . The deck  4  covers the hull  3  from above, and is connected to the hull  3 . A connection line of the hull  3  and the deck  4  is in some cases called a gunnel line. An engine room  10  is provided in the interior of the body  2 , is in communication with a maintenance opening  10   a  provided in the deck  4 , and is opened upward through the maintenance opening  10   a . An engine hood  6  covers the maintenance opening  10   a  from above, and is detachably attached to the deck  4 . 
         [0017]    The personal watercraft  1  is a stand-up type personal watercraft which is steered by the rider in a standing posture. A standing deck  4   a,  and right and left deck fins  4   b,    4   c  are provided at the rear portion of the deck  4 . The standing deck  4   a  has a flat floor surface on which the rider stands. The standing deck  4   a  is located rearward relative to the engine room  10 . The floor surface of the standing deck  4   a  is set to be lower than the upper end of the engine room  10 . The standing deck  4   a  has on the front side thereof, a front wall  4   d  protruding upward and extending in a rightward and leftward direction. The standing deck  4   a  is isolated from the engine room  10  by the front wall  4   d.  The right and left deck fins  4   b,    4   c  are provided on the right side and the left side of the standing deck  4   a,  respectively, to protrude upward and extend in a forward and rearward direction. The front end portions of the right and left standing decks  4   b ,  4   c  are continuous with the front wall  4   d.  The standing deck  4   a  is surrounded by the right and left standing decks  4   b,    4   c,  and the front wall  4   d,  which have a U-shape when viewed from above. 
         [0018]    The front end portion of a handle pole  7  is coupled to the upper surface of the deck  4  in front of the maintenance opening  10   a  in such a manner that handle pole  7  is rotatable around the front end portion. The handle pole  7  is vertically pivotable around the front end portion thereof. A bar-type steering handle  8  is attached onto the rear end portion of the handle pole  7 . A groove  6   a  extending in the forward and rearward direction is provided in the center portion in the rightward and leftward direction of the upper surface of the engine hood  6 . The handle pole  7  is accommodated in the groove  6   a  in a state in which the steering handle  8  is not gripped by the rider. The rider stands on the standing deck  4   a,  grips the steering handle  8 , and moves the handle pole  7  upward. In this state, the rider steers the personal watercraft  1 . 
         [0019]    An engine  11  is placed in the engine room  10 . The output shaft of the engine  11  is connected to a propeller shaft  12  extending rearward in the interior of the body  2 . A water jet pump (not shown) is driven by the propeller shaft  12 . The water jet pump pressurizes and accelerates water suctioned through a suction port provided in the hull  3 . The pressurized and accelerated water is ejected rearward through a jet nozzle  13  attached to the rear end portion of the body  2 . In this way, a forward propulsive force is generated in the body  2 . 
         [0020]    An air cleaner  14 , a battery  15 , and a fuel tank  16  are placed in the engine room  10 . The air cleaner  14  is connected to the intake port of the engine  11  through an air-intake pipe  17 . The battery  15  is configured to store electric power to be supplied to electric components such as a starter motor (not shown) for starting the engine  1 , and a controller (not shown) for controlling the engine  11 . The fuel tank  16  is configured to store fuel to be supplied to the combustion chamber of the engine  11 . The air cleaner  14  is placed rearward relative to the engine  11  and located in the rear portion of the engine room  10 . The battery  15  is placed in front of the engine  11 . The fuel tank  16  is placed in front of the engine  11  and the battery  15 . The fuel tank  11  is located in the front portion of the engine room  10 . Further, a part of an exhaust system  20  (see  FIG. 3 ) of the engine  11  is placed in the engine room  10 . 
         [0021]    As shown in  FIG. 3 , the exhaust system  20  includes a first exhaust pipe  21 , a second exhaust pipe  22 , and a water muffler  30 . The first exhaust pipe  21  includes one pipe member or a plurality of pipe members which are coupled to each other. The second exhaust pipe  22  has the same structure. 
         [0022]    The first exhaust pipe  21  connects the exhaust port of the engine  11  to a water muffler  30  and serves to guide an exhaust gas emitted from the engine  11  to the water muffler  30 . The exhaust gas flows through the water muffler  30 , and thereby a noise of the exhaust gas is reduced. The second exhaust pipe  22  serves to guide the exhaust gas which has flowed through the water muffler  30  outside of the watercraft. The upstream end of the second exhaust pipe  22  is connected to the water muffler  30 , while the downstream end of the second exhaust pipe  22  is opened at the stern. The exhaust gas emitted from the engine  11  flows through the first exhaust pipe  21 , the water muffler  30 , and the second exhaust pipe  22  in this order, and is discharged outside of the watercraft. 
         [0023]    The temperatures of the components included in the exhaust system  20  are elevated by exhaust heat radiated from the engine  11 . The exhaust system  20  includes a cooling water passage through which cooling water flows, in addition to an exhaust passage through which the exhaust gas flows. Water surrounding the personal watercraft  1  is used as the cooling water. The temperatures of the components included in the exhaust system  20  and the temperature of the exhaust gas can be lowered by cooling using the water. 
         [0024]    The structure of the water muffler  30  will now be described. A muffler body  31  of the water muffler  30  has a cylindrical shape. The muffler body  31  includes a first side wall  31   a  located on a first side (one side) in an axial direction, a second side wall  3  lb located on a second side (the other side) in the axial direction, and a peripheral wall  31   c  connecting the side walls  31   a,    31   b  to each other, and having a circular cross-section. The muffler body  31  has an inner space surrounded by the walls  31   a  to  31   c.  The muffler body  31  includes a first separating wall  32  and a second separating wall  33  which are placed in an inner space thereof to be spaced apart from each other in the axial direction. The inner space of the muffler body  31  is separated into three chambers  34  to  36  arranged in the axial direction, by the separating walls  32 ,  33 . The first chamber  34  is in communication with the second chamber  35  via a first communicating portion  37 . The second chamber  35  is in communication with the third chamber  36  via a second communicating portion  38 . 
         [0025]    The first chamber  34  is placed between the second chamber  35  and the third chamber  36  in the axial direction and surrounded by the two separating walls  32 ,  33 . The first separating wall  32  and the third chamber  36  are placed on the first side in the axial direction. The second separating wall  33  and the second chamber  35  are placed on the second side in the axial direction. The first communicating portion  37  is constituted by a pipe or a through-hole provided on the second separating wall  33 . The second communicating portion  38  is constituted by a pipe penetrating the first separating wall  32  and the second separating wall  33  and extending through the interior of the first chamber  34 . 
         [0026]    The water muffler  30  includes an inlet pipe  41  and an outlet pipe  42 . The upstream end portion of the inlet pipe  41  is connected to the downstream end portion of the first exhaust pipe  21 . The downstream end portion of the inlet pipe  41  is opened in the first chamber  34 . The upstream end portion of the outlet pipe  42  is opened in the third chamber  36 . The downstream end portion of the outlet pipe  42  is connected to the upstream end portion of the second exhaust pipe  22 . The exhaust gas emitted from the first exhaust pipe  21  flows through the inlet pipe  41 , the first chamber  34 , the first communicating portion  37 , the second chamber  35 , the second communicating portion  38 , the third chamber  36 , and the outlet pipe  42 , and into the second exhaust pipe  22 . 
         [0027]    The inlet pipe  41  penetrates the first side wall  31   a  and the first separating wall  32  and extends through the interior of the third chamber  36 . The inlet pipe  41  protrudes from the first side wall  31   a  in a first direction (one direction) of the axial direction and is connected to the first exhaust pipe  21  in a location that is apart from the muffler body  31  in the first direction of the axial direction. The outlet pipe  42  protrudes radially from the peripheral wall  31   c  and is connected to the second exhaust pipe  22  in a location that is radially apart from the muffler body  31 . Since the inlet pipe  41  penetrates the first side wall  31   a  located on the first side in the axial direction and the third chamber  36  is located on the first side in the axial direction, the outlet pipe  42  is close to the inlet pipe  41  in the axial direction. For example, in a case where the water muffler  30  is placed in the interior of the body  2  in such a manner that the axial direction of the water muffler  30  conforms to the forward and rearward direction, the inlet pipe  41  and the outlet pipe  42  are placed in the front portion of the water muffler  30 . 
         [0028]    As shown in  FIG. 4A , the inlet pipe  41  has a double-walled pipe structure. The inlet pipe  41  includes a center pipe  43  and an outer pipe  44 . The center pipe  43  has a center pipe wall  45 . The outer pipe  44  has an outer pipe wall  46 . An exhaust passage  47  through which the exhaust gas flows is provided inside the center pipe wall  45 . A water passage  48  through which the cooling water flows is provided between the outer peripheral surface of the center pipe wall  45  and the inner peripheral surface of the outer pipe wall  46 . As shown in  FIG. 4B , the center pipe  43  and the outer pipe  44  are circular pipes, respectively, and are disposed coaxially with each other. The common axis of the pipes  43 ,  44  is a center C 41  of the inlet pipe  41 . The exhaust passage  47  has a circular cross-section. The water passage  48  has a ring-shaped cross-section. 
         [0029]    The downstream end portion of the inlet pipe  41  is formed with an outlet  49  (hereinafter referred to as an exhaust gas outlet  49 ) of the exhaust passage  47 , and an outlet  50  (hereinafter referred to as a water outlet  50 ) of the water passage  48 . The downstream end of the center pipe  43  is opened to form the exhaust gas outlet  49 . The downstream end of the outer pipe  44  (the downstream end of the water passage  48 ) is closed by a ring-shaped closing plate  51 . The water outlet  50  includes at least one through-hole formed to penetrate the closing plate  51 . The through-hole (the water outlet  50 ) is, for example, a circular hole. In a case where the water outlet  50  includes a plurality of through-holes, the plurality of through-holes are arranged at equal intervals in the circumferential direction of the closing plate  51 . 
         [0030]    The center pipe wall  45  has a protruding portion  45   a  protruding from the outer pipe wall  46 , at a downstream end portion of the inlet pipe  41 . In this structure, the water outlet  50  is located to be apart from the exhaust gas outlet  49  in the axial direction of the inlet pipe  41 . A distance from the first separating wall  32  to the exhaust gas outlet  49  is set to be longer than a distance from the first separating wall  32  to the water outlet  50 . The outer peripheral surface of the center pipe  43  includes an exposed portion which is exposed in the first chamber  34 . The ring-shaped closing plate  51  is externally fitted to the center pipe  43 . The inner peripheral edge of the closing plate  51  is integrated with the outer peripheral surface of the center pipe  43 . The outer surface of the closing plate  51  is exposed in the first chamber  34 . The outer surface of the closing plate  51  is made closer to the first separating wall  32  than the downstream end of the center pipe  43  is. 
         [0031]    As shown in  FIGS. 4A and 4D , the center pipe  43  has a radially protruding portion  52  which radially protrudes, at the downstream end portion thereof. The radially protruding portion  52  is placed to overlap with the water outlet  50  when viewed from the axial direction of the inlet pipe  41 . 
         [0032]    As shown in  FIG. 4A , in a state in which the water muffler  30  is incorporated into the body  2 , the inlet pipe  41  is inclined downward toward a downstream side. As shown in  FIG. 5 , the center C 41  of the exhaust gas outlet  49  is placed above the center C 31  of the muffler body  31 . Also, the center C 41  of the exhaust gas outlet  49  is apart from the center C 31  of the muffler body  31  in the rightward and leftward direction. In the present embodiment, the first exhaust pipe  21  is placed on the left side of the engine  11 . In the same manner, the center C 41  of the exhaust gas outlet  49  is apart from the center C 31  of the muffler body  31 , to the left. Alternatively, in a case where the first exhaust pipe  21  is placed at the right side, the center C 41  of the exhaust gas outlet  49  may be apart from the center C of the muffler body  31 , to the right. 
         [0033]    In the water muffler  30  having the above-described configuration, the center pipe wall  45  has the protruding portion  45   a  protruding from the outer pipe wall  46 , at the downstream end portion of the inlet pipe  41 . The water outlet  50  is placed to be apart from the exhaust gas outlet  49  in the axial direction of the inlet pipe  41 . Since the water outlet  50  is placed to be apart from the exhaust gas outlet  49  in the axial direction of the inlet pipe  41 , the cooling water does not easily reach the exhaust gas outlet  49  after the cooling water has flowed through the water passage  48  and into the inner space (the first chamber  34 ) of the muffler body  31  through the water outlet  50 . Therefore, the cooling water does not easily flow back through the exhaust passage  47 . 
         [0034]    In particular, the protruding portion  45   a  is provided with the radially protruding portion  52  which radially protrudes. In this structure, even when the cooling water which has passed through the water outlet  50  flows toward the exhaust gas outlet  49  along the outer peripheral surface of the protruding portion  45   a,  this cooling water can be caused to collide with the radially protruding portion  52 . Thus, the cooling water does not reach the exhaust gas outlet  49  and can be diffused in the radial direction of the inlet pipe  41 . As a result, the cooling water does not easily flow back through the exhaust passage  47 . In the present embodiment, the radially protruding portion  52  overlaps with the water outlet  50  in the axial direction of the inlet pipe  41 . The radially protruding portion  52  can suitably prevent the back flow of the cooling water through the exhaust passage  47 . 
         [0035]    Further, the inlet pipe  41  is inclined downward toward the downstream side. Even if the cooling water flows into the exhaust passage  47 , the cooling water can be discharged from the exhaust passage  47  by a gravitational force. This makes it possible to prevent the backflow of the cooling water. The center C 41  of the exhaust gas outlet  49  is placed above the center C 31  of the muffler body  31 . In this structure, even if the cooling water ejected from the water outlet  50  is accumulated in the interior of the water muffler  30 , it becomes possible to prevent the back flow of the accumulated cooling water through the exhaust passage  47 . 
         [0036]    Turning back to  FIGS. 1 to 3 , the water muffler  30  is placed at the left part of the body  2  with respect to a center line C of the body  2 , in a rightward and leftward direction. The first exhaust pipe  21  is placed on the left side of the engine  11  and extends rearward from the engine  11 . The water muffler  30  is placed rearward relative to the engine room  10 . More specifically, the water muffler  30  is placed to overlap with the left deck fin  4   c  when viewed from above (see  FIG. 1 ). The water muffler  30  is placed below the left deck fin  4   c  and accommodated in the interior of the hull  3  (see  FIG. 2 ). The first side wall  31   a  faces the front, while the second side wall  31   b  faces the rear (see  FIGS. 2 and 3 ). The inlet pipe  41  protrudes forward from the first side wall  31   a  (see  FIGS. 2 and 3 ). The downstream end portion of the first exhaust pipe  21  is connected to the inlet pipe  41  from the front (see  FIGS. 2 and 3 ). 
         [0037]    The outlet pipe  42  protrudes upward from a first portion (i.e., front portion) of the water muffler  30  in the axial direction (see  FIG. 1 ). The second exhaust pipe  22  includes a transverse pipe member  23  connected to the water muffler  30 , and a downstream pipe member  24  connected to the downstream end portion of the transverse pipe member  23  (see  FIGS. 1 to 3 ). The downstream end portion of the transverse pipe member  23  and the upstream end portion of the downstream pipe member  24  are connected to each other by a flange  25  as a pipe joint (see  FIGS. 1 to 3 ). The outer diameter of the flange  25  is set to be larger than that of the transverse pipe member  23  and that of the downstream pipe member  24 . 
         [0038]    The transverse pipe member  23  is connected to the downstream end portion of the outlet pipe  42 , and extends in the rightward and leftward direction in the interior of the engine room  10  (see  FIGS. 1 and 2 ). More specifically, the transverse pipe member  23  extends in the rightward and leftward direction within a slight clearance in the forward and rearward direction, which is formed between the front wall which isolates the standing deck  4   a  from the engine room  10 , and the air cleaner placed rearward relative to the engine  11  in the interior of the engine room  10 . The transverse pipe member  23  is made of rubber and has an elasticity. The downstream end portion of the transverse pipe member  23  is connected to the upstream end portion of the downstream pipe member  24  via the flange  25 . The downstream pipe member  24  extends rearward and is placed in the interior of the right deck fin  4   b.  The inner spaces of the right and left deck fins  4   b,    4   c  cannot be accessed easily by a user, but are spatially in communication with the engine room  10 . Since the exhaust system  20  includes the transverse pipe member which allows the left part and right part of the body  2  to be in communication with each other, it becomes possible to prevent the backflow of the water toward the engine through the exhaust pipe, even if the personal watercraft  1  is inverted to the left or to the right. 
         [0039]    The second exhaust pipe  22  includes a swelling portion  22   a  protruding upward. Because of the presence of the swelling portion  22   a,  it becomes possible to prevent a situation in which the water reaches a portion of the second exhaust pipe  22  which is upstream of the swelling portion  22   a  even when the water outside the watercraft flows forward through the downstream end portion of the second exhaust pipe  22  as backflow. In this way, the water muffler  30  and the engine  11  can be protected. 
         [0040]    The swelling portion  22   a  is provided at the downstream pipe member  24 . The upstream end portion of the downstream pipe member  24  and the flange  25  are placed below the top portion of the swelling portion  22   a  (see  FIG. 1 ). The upstream portion of the second exhaust pipe  22  has an inverted-U shape. 
         [0041]    The swelling portion  22   a  is accommodated in the interior of the right deck fin  4   b . The upstream end portion of the downstream pipe member  24  is placed in front of the top portion of the swelling portion  22   a.  The upstream end portion of the downstream pipe member  24  and the flange  25  are placed at the front end portion of the right deck fin  4   b  or slightly in front of the front end portion of the right deck fin  4   b.    
         [0042]      FIG. 6A  is a cross-sectional view of the right deck fin  4   b,  in a region which is in the vicinity of the flange  25 , when viewed from the front.  FIG. 6B  is a cross-sectional view of the right deck fin  4   b,  in a region which is in the vicinity of the top portion of the swelling portion  22   a,  when viewed from the front. As shown in  FIG. 6B , the top portion of the swelling portion  22   a  is close to the inner surface of the top portion of the right deck fin  4   b.  In contrast, the upstream end portion of the downstream pipe member  24  is vertically apart from the inner surface of the top portion of the right deck fin  4   b.  The width of the right deck fin  4   b  is reduced in the rightward and leftward direction as the right deck fin  4   b  extends upward. In a case where the deck  4  is manufactured by molding, the right deck fin  4   b  is designed to have the above-described width, because it is necessary to provide a draft angle. 
         [0043]    If the transverse pipe member  23  and the downstream pipe member  24  are connected to each other at the top portion of the swelling portion  22   a,  the top portion of the right deck fin  4   b  is required to have a great lateral width so that the flange  25  can be accommodated therein. Since the right deck fin  4   b  is required to be provided with the draft angle, the lower portion of the right deck fin  4   b  is expanded. This may lead to reduction of the width of the standing deck  4   a.  In the present embodiment, the flange  25  is placed at the lower portion of the right deck fin  4   b.  This makes it possible to reduce the width of the right deck fin  4   b,  and increase the width of the standing deck  4   a.  As a result, the stand-up type personal watercraft  1  which can be steered easily by the rider can be realized. 
         [0044]    The water muffler  30  is placed rearward relative to the engine  11  (see  FIG. 1 ). The inlet pipe  41  is provided on the first side wall  31   a  (front wall) of the muffler body  31  so that the inlet pipe  41  can be linearly connected to the first exhaust pipe  21 . On the front side of the muffler body  31 , the third chamber  36 , which is a furthest downstream chamber of the chambers  34  to  36 , is placed (see  FIG. 3 ). For this reason, the outlet pipe  42  is also placed at the front portion of the water muffler  30 . Since the outlet pipe  42  is placed at the front portion of the water muffler  30 , the upstream portion of the second exhaust pipe  22  is made close to the engine  11 . In this layout, the water muffler  30  can be placed below the right deck fin  4   b,  and the upstream portion of the second exhaust pipe  22  can be placed in front of the standing deck  4   a . Also, the upstream portion of the second exhaust pipe  22  can be placed in the engine room  10 . In the rear end portion of the engine room  10 , a gap is formed between the separating wall and the air cleaner  14 . The transverse pipe member  23  can be extended through this gap. In this way, the transverse pipe member  23  can be placed while avoiding interference with the propeller shaft  12 . The transverse pipe member  23  is made of rubber, and is bendable. Therefore, the transverse pipe member  23  can be easily placed in a narrow space. In addition, an operation for connecting the water muffler  30  and the downstream pipe member  24  to each other can be performed easily by use of the transverse pipe member  23 . 
         [0045]    The above-described configuration and illustration are merely exemplary, and can be changed within the scope of the invention. Although in the example of  FIG. 4A , the closing plate  51  is located to be apart from the first separating wall  32  in the axial direction, in the interior of the first chamber, the closing plate  51  may be coplanar with the first separating wall  32 . In the example of  FIG. 4D , the radially protruding portion  52  protrudes radially from the entire periphery of the protruding portion  45  and has the ring-shape, when viewed from the axial direction of the inlet pipe  41 . However, it is sufficient that the radially protruding portion  52  overlaps with the water outlet  50 , when viewed from the axial direction of the inlet pipe  41 . As shown in  FIGS. 4A and 4D , in the case where the plurality of water outlets  50  are arranged to be spaced apart from each other in the circumferential direction, a plurality of radially protruding portions  52  may be provided to protrude from a plurality of locations, respectively, on the outer peripheral surface of the protruding portion  45   a.  The cross-section of each of the muffler body  31  and the inlet pipe  41  need not have a circular shape. The configuration in which the exhaust gas outlet is placed above the center of the muffler body is merely exemplary. Alternatively, the exhaust gas outlet may be placed below the center of the muffler body.