Patent Publication Number: US-7223138-B2

Title: Water jet propeller

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   The present application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2004-264215, filed Sep. 10, 2004, the entire contents of which are hereby incorporated by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a water jet propeller having an impeller disposed inside an impeller housing and making the impeller rotate to expel a water jet. 
   2. Description of Background Art 
   Conventionally, the water jet propeller is mounted in a rear portion of a hull and draws in water from a hull bottom by driving the impeller with an engine and expelling the water drawn therein rearward, thereby propelling a watercraft See, for example, Japanese Patent Laid-open No. Hei 9-99897. 
   The art disclosed in Japanese Patent Laid-open No. Hei 9-99897 will be described with reference to  FIG. 11 . 
     FIG. 11  is a view for illustrating a basic construction of the conventional water jet propeller. 
   A water jet propeller  200  includes an impeller housing  203 , a stator  204 , a nozzle  205 , and a steering nozzle  207 . The impeller housing  203 , of a cylindrical shape, is disposed in a rear portion  202  of a hull  201 . The stator  204 , of a cylindrical shape, is disposed at a rear-end portion  203   a  of the impeller housing  203 . The nozzle  205  having a diminishing diameter rearwardly is disposed at a rear-end portion  204   a  of the stator  204 . The steering nozzle  207  is fitted to the nozzle  205  via upper and lower pins  206 ,  206  swingably in a crosswise direction. 
   An impeller  208  is disposed inside the impeller housing  203 . A rotational shaft  209  of the impeller  208  is extended to reach into the stator  204 . The extended rotational shaft  209  is rotatably mounted in the stator  204  via bearings  211 ,  211 . 
   According to the water jet propeller  200 , the impeller  208  disposed inside the impeller housing  203  is rotated by an engine (not shown). A water jet is thereby expelled from a rear-end portion  207   a  of the steering nozzle  207  to propel the hull  201 . 
   The steering nozzle  207  is swung to the right or to the left about an axis of the upper and lower pins  206 ,  206 , thereby allowing the hull  201  to turn right or left. 
   The water jet propeller  200  generally uses a connection bolt (not shown) as means for mounting the impeller housing  203 , the stator  204 , and the nozzle  205  integrally together. 
   More specifically, each of the impeller housing  203 , the stator  204 , and the nozzle  205  includes a mounting portion (not shown) disposed on an outer wall thereof. The connection bolt is passed through the mounting portion of the impeller housing  203 , the mounting portion of the stator  204 , and the mounting portion of the nozzle  205 . The impeller housing  203 , the stator  204 , and the nozzle  205  are thereby connected integrally together. 
   The water jet propeller  200  may be disassembled for purposes of, for example, performing a service job, by removing the connection bolt. In such cases, the impeller housing  203 , the stator  204 , and the nozzle  205  can be separated from each other. 
   It is to be noted herein that the rotational shaft  209  of the impeller  208  is extended to reach into the stator  204 . The extended rotational shaft  209  is rotatably mounted in the stator  204  via the bearings  211 ,  211 . 
   Accordingly, when the impeller housing  203 , the stator  204 , and the nozzle  205  are separated from each other, the impeller  208  and the stator  204  are integrally separated from the impeller housing  203  or the nozzle  205 . 
   As a result, the impeller  208  is removed from the impeller housing  203  and exposed. 
   It is therefore an object of the present invention to provide a water jet propeller that prevents the impeller from being exposed when the water jet propeller is disassembled. 
   SUMMARY AND OBJECTS OF THE INVENTION 
   To achieve the foregoing object, according to a first aspect of the present invention, there is provided a water jet propeller including: a cylindrically shaped impeller housing disposed in a rear portion of a hull; an impeller disposed inside the impeller housing; a cylindrically shaped stator disposed at a rear-end portion of the impeller housing; and a nozzle disposed at a rear-end portion of the stator, the nozzle having a diameter that gradually diminishes rearwardly. The water jet propeller propels the hull by expelling a water jet from a rear-end portion of the nozzle by rotating the impeller. The water jet propeller is characterized in the following points. Specifically, the impeller is rotatably mounted to the stator, being disposed inside the impeller housing; the impeller housing, the stator, and the nozzle are connected integrally with each other using a first bolt; and the impeller housing and the stator are connected integrally with each other using a second bolt. 
   The impeller is rotatably mounted to the stator and disposed inside the impeller housing. Further, the impeller housing and the stator are connected integrally with each other using the second bolt. 
   Accordingly, the impeller housing and the stator are kept in a state of being connected to each other when the first bolt is removed. This keeps the impeller housed inside the impeller housing, preventing the impeller from being exposed. 
   According to a second aspect of the present invention, the water jet propeller is characterized in that a head portion of the first bolt is disposed to face rearwardly of the hull and that a head portion of the second bolt is disposed to face forwardly of the hull. 
   The head portion of the first bolt is disposed to face rearwardly of the hull. This arrangement allows a removal tool to be simply mounted onto the head portion of the first bolt from a rearward direction of the hull. The first bolt can thus be removed and reinstalled simply and in a trouble-free manner. 
   The head portion of the second bolt is disposed to face forwardly of the hull. This arrangement makes the head portion of the second bolt invisible from the rear when the removal tool is mounted on the head portion of the first bolt from the rearward direction of the hull. 
   The arrangement, in which the head portion of the second bolt is invisible from the rear, prevents the second bolt from being inadvertently removed. 
   According to a third aspect of the present invention, the water jet propeller is characterized in the following points. Specifically, the stator includes a water take-out path, through which water in the stator is taken out externally, disposed on an outer wall of the stator; the impeller housing includes a water guide path in communication with the water take-out path, the water guide path being disposed on an outer wall of the impeller housing; a first protruding tab and a second protruding tab are disposed on a wall portion forming the water take-out path and a wall portion forming the water guide path, respectively, so as to oppose to each other; and the first and the second protruding tabs are connected together using the second bolt. 
   The first protruding tab and the second protruding tab are disposed on the wall portion forming the water take-out path and the wall portion forming the water guide path, respectively, so as to oppose to each other. The second bolt is mounted in the first and the second protruding tabs. 
   Accordingly, a connection portion between the water take-out path and the water guide path can be positively sealed via the first and the second protruding tabs by tightening the first and the second protruding tabs with the second bolt. 
   The first aspect of the present invention achieves the effect of preventing the impeller from being exposed. 
   According to the second aspect of the present invention, the head portion of the second bolt is not visible from the rear. This achieves the effect of preventing the second bolt from being inadvertently removed. 
   According to the third aspect of the present invention, the connection portion between the water take-out path and the water guide path can be positively sealed via the first and the second protruding tabs. This achieves the effect of efficiently taking out water in the stator externally. 
   Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
       FIG. 1  is a side elevational view showing a personal watercraft including a water jet propeller according to a preferred embodiment of the present invention; 
       FIG. 2  is a cross-sectional view showing the water jet propeller according to the preferred embodiment of the present invention; 
       FIG. 3  is a cross-sectional view showing an impeller housing, a liner, and a stator of the water jet propeller according to the preferred embodiment of the present invention; 
       FIG. 4  is an exploded perspective view showing the water jet propeller according to the preferred embodiment of the present invention; 
       FIG. 5  is a side elevational view showing the water jet propeller according to the preferred embodiment of the present invention; 
       FIG. 6  is a rear view showing the water jet propeller according to the preferred embodiment of the present invention; 
       FIG. 7  is a cross-sectional view taken along line  7 — 7  of  FIG. 6 ; 
       FIG. 8  is a view for illustrating a condition, in which connection bolts are removed from the water jet propeller according to the preferred embodiment of the present invention; 
       FIG. 9  is a view for illustrating a condition, in which connection bolts are removed from a water jet propeller according to a modified example of the present invention; 
       FIG. 10  is a view for illustrating the operation of the water jet propeller according to the preferred embodiment of the present invention; and 
       FIG. 11  is a view for illustrating a basic construction of a conventional water jet propeller. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   A specific embodiment to which the present invention is applied will be described below with reference to the accompanying drawings. For the purpose of this specification, “front,” “rear,” “left,” and “right” denote corresponding directions as viewed from an operator of a watercraft. In addition, “Fr” denotes forward, “Rr” denotes rearward, “L” denotes leftward, and “R” denotes rightward. 
     FIG. 1  is a side elevational view showing a personal watercraft including a water jet propeller according to a preferred embodiment of the present invention. 
   A personal watercraft  10  includes a fuel tank  13 , an engine  14 , a water jet propeller chamber  16 , and a water jet propeller  20 . The fuel tank  13  is mounted in a front portion  12  of a hull  11 . The engine  14  is disposed rearward of the fuel tank  13 . The water jet propeller chamber  16  is disposed at a stern (a rear portion of the hull)  15  located rearward of the engine  14 . The water jet propeller  20  is disposed inside the water jet propeller chamber  16 . 
   The personal watercraft  10  further includes a steering nozzle  21 , a steering handlebar  22 , and a seat  23 . The steering nozzle  21  is disposed rearward of the water jet propeller  20  and mounted swingably to the right and left via upper and lower pins  18 ,  19 . The steering handlebar  22  for swingably operating the steering nozzle  21  is disposed upward of the fuel tank  13 . The seat  23  is disposed rearward of the steering handlebar  22 . 
     FIG. 2  is a cross-sectional view showing the water jet propeller according to the preferred embodiment of the present invention. 
   The water jet propeller  20  is constructed as follows. Specifically, the stem  15  of the hull  11  includes an intake port  25  (shown in  FIG. 1 ) of a water flow duct  24  that opens to a hull bottom  17 . The water flow duct  24  is extended to the water jet propeller chamber  16 . First and second bases  27 ,  28  are mounted in a wall portion  26  of the water jet propeller chamber  16 . A cylindrical impeller housing  30  is disposed on the first and the second bases  27 ,  28 . A cylindrical stator  32  is disposed on a rear-end portion  30   a  of the impeller housing  30 . Further, a nozzle  34  is disposed at a rear-end portion  32   a  of the stator  32 . The nozzle  34  has a diameter that gradually diminishes rearwardly. 
   Further, an impeller  36  is disposed inside the impeller housing  30 . Female splines  37  of the impeller  36  are engaged onto male splines  39  of a drive shaft  38  to achieve a splined coupling between the impeller  36  and the drive shaft  38 . A front-end of the drive shaft  38  is coupled to the engine  14  (see  FIG. 1 ). A threaded connection is then made between internal threads  41  of the impeller  36  and external threads  43  of a support shaft  42 . The support shaft  42  is rotatably mounted in a bearing  46  of the stator  32  via a bearing  44 . 
   More specifically, the impeller  36  and the support shaft  42  are integrated with each other by making the threaded connection between the internal threads  41  of the impeller  36  and the external threads  43  of the support shaft  42 . 
   The arrangement, in which the support shaft  42  is rotatably mounted in the bearing  46  of the stator  32  via the bearing  44 , means that the impeller  36  is rotatably mounted in the stator  32 . 
   The impeller  36  is disposed, or accommodated, in the impeller housing  30 . 
   The bearing  46  is secured to a casing  49  of the stator  32  via a plurality of stays  48  . . . ( . . . indicates plurality). 
   A cap  68  is mounted to a rear-end portion of the bearing  46  with bolts  69  . . . . 
   The stays  48  are members extending radially from an outer periphery of the bearing  46  to the casing  49  of the stator  32 . 
     FIG. 3  is a cross-sectional view showing disassembled states of the impeller housing, a liner, and the stator of the water jet propeller according to the preferred embodiment of the present invention. An imaginary line representing a liner  53  in  FIG. 3  indicates a state, in which the liner  53  is insert-molded in the impeller housing  30 . 
   In the water jet propeller  20 , the impeller  36  (see  FIG. 2 ) is disposed so as to circumvent a front-end portion  51   a  of an inner periphery  51  of the impeller housing  30 . Further, the liner  53  is disposed over a region  51   b  facing the impeller  36  and representing the inner periphery  51  of the impeller housing  30  less the front-end portion  51   a . The front-end portion  51   a  is formed to have an inside diameter that gradually increases forwardly, or toward the front edge  51   c.    
   By gradually increasing the inside diameter of the front-end portion  51   a  toward the front edge  51   c , the front-end portion  51   a  is formed into a curved cross section. 
   By gradually increasing the inside diameter of the front-end portion  51   a  toward the front edge  51   c  as described above, the front edge  51   c  of the inner periphery  51  is formed to have the same inside diameter as the first base  27  shown in  FIG. 2 . The first base  27  has an inside diameter identical to the inside diameter of a rear-end portion  24   a  of the water flow duct  24 . 
   According, the front edge  51   c  of the inner periphery  51  has an inside diameter identical to the inside diameter of the rear-end portion  24   a  of the water flow duct  24 . 
   The liner  53  is, as an example, a stainless steel cylindrical member molded (insert-molded) in the impeller housing  30 . 
   A positioning pin  29  is used when the rear-end portion  30   a  of the impeller housing  30  is mounted to the stator  32 . A job of assembling the stator  32  to the impeller housing  30  is thereby simplified. 
   Referring back to  FIG. 2 , according to the water jet propeller  20 , the impeller  36  is rotated by rotating the drive shaft  38  with the engine  14  (see  FIG. 1 ). 
   Rotation of the impeller  36  allows water to be drawn into the water flow duct  24  through the intake port  25  (see  FIG. 1 ). The water thus drawn in is then further drawn into the impeller housing  30  via the rear-end portion  24   a  of the water flow duct  24 . 
   Water in the impeller housing  30  is sent to the nozzle  34  via the stator  32  through rotation of the impeller  36 . A water jet is then expelled from a rear-end portion  34   a  of the nozzle  34  rearwardly as shown by an arrow b. 
   Expelling the water jet rearwardly from the rear-end portion  34   a  of the nozzle  34  propels the personal watercraft  10  (shown in  FIG. 1 ). 
     FIG. 4  is an exploded perspective view showing the water jet propeller according to the preferred embodiment of the present invention. 
   The impeller housing  30  is a cylindrically formed member. Four mounting brackets  55  . . . are provided at predetermined intervals on a front-end portion  30   b . Each of the mounting brackets  55  . . . is provided with a mounting hole  56 . A rear flange  57  is formed on the rear-end portion  30   a . Mounting threaded holes  58  . . . (shown in  FIG. 4  are only the left-hand side mounting threaded holes  58 ,  58 ) are formed at all four corners of the rear flange  57 . 
   The impeller housing  30  is constructed as follows. Specifically, a left-hand side portion  61   a  of an outer wall  61  includes a water guide path  62 . A wall portion  63  forming the water guide path  62  includes a left-hand side second protruding tab (a second protruding tab)  64 . The left-hand side second protruding tab  64  includes a mounting hole  65 . A right-hand side portion (not shown) of the outer wall  61 , or a side opposite to the left-hand side second protruding tab  64 , includes a right-hand side second protruding tab  66  (see  FIG. 6 ). The right-hand side second protruding tab  66  includes a mounting hole  67  (see  FIG. 6 ). 
   The liner  53  is, as an example, a stainless steel cylindrical member molded (insert-molded) in the impeller housing  30  when the impeller housing  30  is cast. 
   Forming the liner  53  from the stainless steel that offers outstanding wear resistance helps prevent the inner periphery  51  of the impeller housing  30  from wearing should foreign matter enter between the impeller  36  and the impeller housing  30  during rotation of the impeller  36  (see  FIG. 2 ). 
   The stator  32  is a cylindrically formed member. A front-end portion  32   b  includes a front flange  71 . The front flange  71  is provided with mounting holes  72  . . . disposed at all four corners thereof. The rear-end portion  32   a  of the stator  32  includes a rear flange  73 . The rear flange  73  is provided with mounting holes  74  . . . (the mounting hole  74  at the right bottom corner is not shown) disposed at all four corners thereof. 
   The mounting holes  72  . . . in the front flange  71  and the mounting holes  74  . . . in the rear flange  73  are formed concentrically with each other. 
   The stator  32  is constructed as follows. Specifically, a left-hand side portion  76   a  of an outer wall  76  includes a water take-out portion  77 . The water take-out portion  77  is provided with a water take-out path  78 . A wall portion  81  forming the water take-out path  78  includes a left-hand side first protruding tab (a first protruding tab)  82 . The left-hand side first protruding tab  82  is provided with a mounting threaded hole  83 . A right-hand side portion (not shown) of the outer wall  76 , or a side opposite to the left-hand side first protruding tab  82 , includes a right-hand side first protruding tab  84  (see also  FIG. 6 ). The right-hand side first protruding tab  84  includes a mounting threaded hole  85  (see also  FIG. 6 ). 
   The left-hand side first protruding tab  82  is disposed opposingly to the left-hand side second protruding tab  64 . The right-hand side first protruding tab  84  is disposed opposingly to the right-hand side second protruding tab  66  (see  FIG. 6 ). 
   The water take-out path  78  is a path, through which water in the stator  32  is taken out externally via the water take-out portion  77  and then guided into the water guide path  62 . 
   The water guided up to the water guide path  62  is guided to the engine through a path not shown, used as coolant for cooling the engine. 
   There are known some types of the water jet propeller  20  that integrate the impeller housing  30  with the stator  32 . When the impeller housing  30  is molded integrally with the stator  32 , the resultant molded member becomes relatively large in size and has a complicated shape. 
   Accordingly, integrally molding the impeller housing  30  with the stator  32  requires a mold that is large in size and complicated in shape, thus resulting in equipment cost being increased. 
   The impeller housing  30  and the stator  32  are therefore divided into two parts so that each of the members  30 ,  32  is built compactly and shaped simply. 
   It is then possible to make molds for molding the impeller housing  30  and the stator  32  small and less complicated in shape, thus suppressing the equipment cost. 
   The nozzle  34  is attached to the rear-end portion  32   a  of the stator  32 . 
   The nozzle  34  is formed to have a diameter that gradually diminishes from a front-end portion  34   b  toward the rear-end portion  34   a . The front-end portion  34   b  includes a front flange  91 . The front flange  91  is provided with mounting holes  92  . . . disposed at all four corners thereof. 
   The front-end portion  32   b  of the stator  32  is pressed up against the rear-end portion  30   a  of the impeller housing  30 . The mounting holes  72  . . . in the front flange  71  are thereby aligned with corresponding ones of the mounting threaded holes  58  . . . in the rear flange  57 . 
   Further, pressing the front-end portion  32   b  of the stator  32  up against the rear-end portion  30   a  of the impeller housing  30  results in the following. Specifically, a rear opening end  62   a  of the water guide path  62  is connected to an opening end  78   a  of the water take-out path  78 , thus bringing the water guide path  62  into communication with the water take-out path  78 . At the same time, the left-hand side second protruding tab  64  is abutted against the left-hand side first protruding tab  82 , and the right-hand side second protruding tab  66  (see  FIG. 6 ) is abutted against the right-hand side first protruding tab  84 . 
   Similarly, the front-end portion  34   b  of the nozzle  34  is pressed up against the rear-end portion  32   a  of the stator  32 . The mounting holes  92  in the front flange  91  are then aligned with corresponding ones of the mounting holes  74  in the rear flange  73 . 
   Connection bolts (first bolts)  94  . . . are then inserted into the mounting holes  92  . . . in the front flange  91 , the mounting holes  74  in the rear flange  73 , the mounting holes  72  . . . in the front flange  71 , and the mounting threaded holes  58  . . . in the rear flange  57 . 
   The connection bolt  94  includes a head portion  94   a  disposed at a base end portion and a threaded portion  94   b  at a leading end portion. The threaded portion  94   b  has external threads that can be screw-threadably engaged with the mounting threaded hole  58 . 
   The left-hand side second protruding tab  64  is abutted against the left-hand side first protruding tab  82 . The mounting threaded hole  83  in the left-hand side first protruding tab  82  is thereby aligned with the mounting hole  65  in the left-hand side second protruding tab  64 . 
   A lock bolt  96  is then inserted in the mounting hole  65  in the left-hand side second protruding tab  64  and the mounting threaded hole  83  in the left-hand side first protruding tab  82 . 
   The lock bolt  96  includes a head portion  96   a  disposed at a base end portion and a threaded portion  96   b  at a leading end portion. The threaded portion  96   b  has external threads that can be screw-threadably engaged with the mounting threaded hole  83 . 
     FIG. 5  is a side elevational view showing the water jet propeller according to the preferred embodiment of the present invention.  FIG. 6  is a rear view showing the water jet propeller according to the preferred embodiment of the present invention. 
   The front-end portion  32   b  of the stator  32  is pressed up against the rear-end portion  30   a  of the impeller housing  30 . Further, the front-end portion  34   b  of the nozzle  34  is pressed up against the rear-end portion  32   a  of the stator  32 . 
   In this condition, the connection bolts  94  . . . are inserted into the mounting holes  92  . . . in the nozzle  34 , the mounting holes  74  . . . and the mounting holes  72  in the stator  32 , and the mounting threaded holes  58  . . . in the impeller housing  30 . 
   The threaded portions  94   b  . . . of the connection bolts  94  . . . are then screwed in the corresponding ones of the mounting threaded holes  58  . . . . 
   The stator  32  is thereby clamped between the impeller housing  30  and the nozzle  34 . The impeller housing  30 , the stator  32 , and the nozzle  34  are then connected together using the four connection bolts  94  . . . . 
   In this condition, the head portions  94   a  of the connection bolts  94  . . . are disposed to face rearwardly of the hull  11  (see  FIG. 1 ). 
   Connecting together the impeller housing  30 , the stator  32 , and the nozzle  34  brings the water guide path  62  into communication with the water take-out path  78 . 
   In addition, connecting together the impeller housing  30 , the stator  32 , and the nozzle  34  causes the left-hand side first protruding tab  82  and the left-hand side second protruding tab  64  to oppose each other. Similarly, connecting together the impeller housing  30 , the stator  32 , and the nozzle  34  causes the right-hand side first protruding tab  84  and the right-hand side second protruding tab  66  (see  FIG. 6 ) to oppose each other. 
   The lock bolt (second bolt)  96  is inserted in the mounting hole  65  (see  FIG. 7 ) in the left-hand side second protruding tab  64 . The threaded portion  96   b  protruding from the left-hand side second protruding tab  64  is then screw-threadably engaged with the mounting threaded hole  83  (see  FIG. 7 ) in the left-hand side first protruding tab  82 . 
   Specifically, the left-hand side first protruding tab  82  and the left-hand side second protruding tab  64  are connected together with the lock bolt  96 . 
   Further, referring to  FIG. 6 , the lock bolt (second bolt)  96  is inserted in the mounting hole  67  in the right-hand side second protruding tab  66 . The threaded portion  96   b  protruding from the right-hand side second protruding tab  66  is then screw-threadably engaged with the mounting threaded hole  85  in the right-hand side first protruding tab  84 . 
   Specifically, the right-hand side first protruding tab  84  and the right-hand side second protruding tab  66  are connected together with the lock bolt  96 . 
   Thus, the left-hand side first protruding tab  82  and the left-hand side second protruding tab  64  are connected together with the lock bolt  96 , and the right-hand side first protruding tab  84  and the right-hand side second protruding tab  66  are connected together with the lock bolt  96 . The impeller housing  30  and the stator  32  are thereby connected together with the two lock bolts  96 ,  96 . 
   In this condition, the head portions  96   a ,  96   a  of the lock bolts  96 ,  96  are disposed to face forwardly of the hull  11  (see  FIG. 1 ). 
   Reasons why the impeller housing  30  and the stator  32  are connected together with the two lock bolts  96 ,  96  will be described later in detail with reference to  FIGS. 8 and 9 . 
   In a condition, in which the impeller housing  30 , the stator  32 , and the nozzle  34  are integrated together, the mounting brackets  55  . . . of the impeller housing  30  are pressed against the first and the second bases  27 ,  28  (see  FIG. 2 ). Mounting bolts  98  . . . are then inserted in the mounting holes  56  . . . in the mounting brackets  55  . . . . 
   Threaded portions  98   b  . . . of the mounting bolts  98  . . . protruding from the mounting brackets  55  . . . are then screw-threadably engaged with threaded holes (not shown) in the first and the second bases  27 ,  28 . 
   The impeller housing  30 , the stator  32 , and the nozzle  34  are thereby mounted to the first and the second bases  27 ,  28  with the mounting bolts  98  . . . . 
   In this condition, the mounting bolts  98  . . . are disposed such that head portions  98   a  thereof face rearwardly of the hull  11  (see  FIG. 1 ). 
   The head portions  94   a  . . . of the connection bolts  94  . . . are disposed to face rearwardly of the hull  11  (see  FIG. 1 ). 
   This arrangement allows the connection bolts  94  . . . to be removed and reinstalled simply and in a trouble-free manner by simply attaching a removal tool onto the head portions  94   a  . . . of the connection bolts  94  . . . from a rearward direction of the hull  11 . 
   Similarly, the head portions  98   a  . . . of the mounting bolts  98  . . . are disposed to face rearwardly of the hull  111  (see  FIG. 1 ). 
   This arrangement allows the mounting bolts  98  . . . to be removed and reinstalled simply and in a trouble-free manner by simply attaching a removal tool onto the head portions  98   a  . . . of the mounting bolts  98  . . . from a rearward direction of the hull  11 . 
   Similarly, the head portions  96   a ,  96   a  of the lock bolts  96 ,  96  are disposed to face forwardly of the hull  11  (see  FIG. 1 ). 
   This arrangement makes the head portions  96   a ,  96   a  of the lock bolts  96 ,  96  invisible from the rear when the removal tool is mounted on the head portions  94   a  . . . of the connection bolts  94  . . . or the head portions  98   a  . . . of the mounting bolts  98  . . . from the rearward direction of the hull  11 . 
   The arrangement, in which the head portions  96   a ,  96   a  of the lock bolts  96 ,  96  are invisible from the rear, prevents the lock bolts  96 ,  96  from being inadvertently removed. 
     FIG. 7  is a cross-sectional view taken along line  7 — 7  of  FIG. 6 . 
   The lock bolt  96  is inserted in the mounting hole  65  in the left-hand side second protruding tab  64 . The threaded portion  96   b  protruding from the left-hand side second protruding tab  64  is then screw-threadably engaged with the mounting threaded hole  83  in the left-hand side first protruding tab  82 . 
   The lock bolt  96  is tightened with the left-hand side second protruding tab  64  being opposed to the left-hand side first protruding tab  82 . 
   It should be noted herein that the left-hand side second protruding tab  64  is formed integrally with the wall portion  63  of the water guide path  62  and the left-hand side first protruding tab  82  is formed integrally with the wall portion  81  of the water take-out path  78 . 
   Accordingly, the lock bolt  96  is tightened with the left-hand side second protruding tab  64  and the left-hand side first protruding tab  82  being opposed to each other. The lock bolt  96  is therefore tightened in a condition, in which the opening end  78   a  of the water take-out path  78  and the rear opening end  62   a  of the water guide path  62  are in abutment with each other by way of the left-hand side second protruding tab  64  and the left-hand side first protruding tab  82 . 
   This achieves a positive sealing of an abutment portion (connection portion)  99  between the opening end  78   a  of the water take-out path  78  and the rear opening end  62   a  of the water guide path  62  using a sealing material  101 . 
   The water take-out path  78  is in communication with a space  77   a  of the water take-out portion  77 . The space  77   a  is in communication with the stator  32  via small holes  79  . . . . 
   Accordingly, water in the stator  32  is led into the space  77   a  via the small holes  79  . . . and the water led into the space  77   a  is guided to the water guide path  62  via the water take-out path  78 . 
   The reasons why the impeller housing  30  and the stator  32  are connected together with the two lock bolts will be described in detail below with reference to  FIGS. 8 and 9 . 
     FIG. 8  is a view for illustrating a condition, in which the connection bolts are removed from the water jet propeller according to the preferred embodiment of the present invention. 
   A threaded connection is made between the impeller  36  of the water jet propeller  20  and the support shaft  42  (see  FIG. 2 ). The support shaft  42  is then rotatably mounted in the stator  32 . The impeller  36  is then accommodated in the impeller housing  30 . 
   In this condition, the impeller housing  30  and the stator  32  are connected integrally using the lock bolts  96 ,  96 . 
   Accordingly, when the connection bolts  94  . . . are removed to separate the water jet propeller  20 , a condition, in which the impeller housing  30  and the stator  32  are connected together, is retained. 
   Accordingly, a condition, in which the impeller  36  is stored inside the impeller housing  30 , is retained, thus preventing the impeller  36  from being exposed. 
     FIG. 9  is a view for illustrating a condition, in which connection bolts are removed from a water jet propeller according to a modified example of the present invention. 
   A threaded connection is made between an impeller  251  of a water jet propeller  250  and a support shaft  252 . The support shaft  252  is then rotatably mounted in a stator  253 . The impeller  251  is then accommodated in an impeller housing  254 . 
   In this condition, the impeller housing  254 , the stator  253 , and a nozzle  255  are connected integrally together using connection bolts  266  . . . . 
   When the connection bolts  266  . . . are removed to separate the water jet propeller  250 , therefore, the impeller housing  254  is separated from the stator  253 . 
   As a result, the impeller housing  254  is separated from the impeller  251 , thus exposing the impeller  251 . 
   An example, in which the water jet propeller propels the personal watercraft, will be described with reference to  FIG. 10 . 
     FIG. 10  is a view for illustrating the operation of the water jet propeller according to the preferred embodiment of the present invention. 
   The water jet propeller  20  includes the liner  53  that is applied to the region  51   b  facing the impeller  36  and representing the inner periphery  51  of the impeller housing  30  less the front-end portion  51   a . The inside diameter of the front-end portion  51   a  not lined with the liner  53  is made to increase gradually toward the front edge  51   c . The front-end portion  51   a  is thus formed into a curved cross section. 
   The front edge  51   c  of the inner periphery  51  is formed to have an inside diameter identical to the inside diameter of the first base  27  and the inside diameter of the rear-end portion  24   a  of the water flow duct  24 . 
   Accordingly, even if the inside diameter of the region  51   b  facing the impeller  36  and representing the inner periphery  51  of the impeller housing  30  less the front-end portion  51   a , is made smaller than the inner periphery of the rear-end portion  24   a  of the water flow duct  24 , there is produced no step in the first base  27 , the rear-end portion  24   a  of the water flow duct  24 , and the front edge  51   c  of the inner periphery  51 . 
   This permits an efficient inflow of water in the direction shown by the arrow in  FIG. 10  from the rear-end portion  24   a  of the water flow duct  24  to the impeller housing  30  by way of the first base  27  and the front-end portion  51   a  of the inner periphery  51 . 
   It is easily conceivable that foreign matter (not shown) enters between the impeller  36  and the impeller housing  30  during rotation of the impeller  36 . 
   The water jet propeller  20  therefore includes the stainless steel liner  53  that is applied to the region  51   b  facing the impeller  36  and representing the inner periphery  51  of the impeller housing  30  less the front-end portion  51   a.    
   This enhances wear resistance of the region  51   b  facing the impeller  36  and representing the inner periphery  51  of the impeller housing  30  less the front-end portion  51   a . It is also possible to suppress wear of the liner  53 , should foreign matter (not shown) enter between the impeller  36  and the impeller housing  30 . 
   The preferred embodiment of the present invention has been described using an exemplary case, in which four connection bolts  94  . . . are used to integrally connect the impeller housing  30 , the stator  32 , and the nozzle  34 . It should be noted that the number of the connection bolts  94  . . . is not limited to four; rather, any number of the connection bolts  94  . . . may be used. 
   The preferred embodiment of the present invention has been described using an exemplary case, in which two lock bolts  96  . . . are used to integrally connect the impeller housing  30  and the stator  32 . It should be noted that the number of the lock bolts  96  . . . is not limited to four; rather, any number of the lock bolts  96  . . . may be used. 
   Further, according to the preferred embodiment of the present invention described as an exemplary case in the foregoing, the water take-out path  78  is mounted to the left of the stator  32  and the water guide path  62  is mounted to the left of the impeller housing  30 . It should be noted, however, that the positions at which the water take-out path  78  and the water guide path  62  are disposed at not limited to the exemplary case. Rather, the water take-out path  78  and the water guide path  62  may be disposed at any other locations. 
   The present invention can be preferably applied to a water jet propeller having an impeller housing disposed at a rear portion of a hull and making an impeller disposed inside the impeller housing rotate to expel a water jet. 
   The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.