Patent Publication Number: US-6902451-B1

Title: Marine propulsion system with vertical adjustment without requiring a U-joint

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a marine propulsion system and, more particularly, to a stern drive unit that provides the capability of adjusting the propeller position vertically without the necessity of providing a U-joint to permit this capability. 
     2. Description of the Prior Art 
     Those skilled in the art of marine propulsion systems are aware that most stern drive systems require the use of a U-joint to allow the marine propulsion system to be trimmed, tilted, and steered. Those skilled in the art are also aware that most known stern drive systems do not allow the propeller to be raised or lowered from its normal position without also trimming the drive unit. In addition, those skilled in the art are aware that the steering axis of most known stern drive systems is closer to the transom of a marine vessel than to the intersection between the propeller shaft and the drive shaft which is connected to the propeller shaft. 
     U.S. Pat. No. 5,647,780, which issued to Hosoi on Jul. 15, 1997, describes a vertically adjustable stern drive for a water craft. The marine stern drive includes a tilt/trim and lift adjustment mechanism which raises and lowers the drive while maintaining an established trim angle. The adjustment mechanism includes a parallelogram linkage system. An upper lever of the linkage system is defined in part by a pair of tilt and trim actuators which vary the length of the upper linkage to adjust the trim position of the stern drive and for tilt up. A lower lever of the linkage system is defined between two flexible couplings of a propulsion drive train. One of the flexible couplings is coupled to a lower drive unit of the stern drive which permits the lower lever to rotate without changing the trim angle of the lower drive unit. 
     U.S. Pat. No. 4,297,097, which issued to Kiekhaefer on Oct. 27, 1981, discloses a stern drive mechanism. The stern drive installation includes a mounting bracket assembly for securing to the transom of a watercraft. The bracket assembly is provided with a transverse horizontal bore rearwardly of the transom for receiving one end of the horizontal cylinder portion of the upper housing of the drive unit. A bracket assembly addition is provided with a horizontal bore which rotatably receives the opposite end of the horizontal cylindrical portion of the upper housing and is secured to the bracket assembly. The bracket assembly and the addition thereto serve to rotatably support the drive unit and provide for tilt movement of the unit on a horizontal transverse axis. The lower housing of the drive unit is dirigibly connected to the upper housing for support and to provide for pivotal movement of the lower housing relative to the upper housing to provide for steering control of the water craft. 
     U.S. Pat. No. 6,019,649, which issued to Friesen et al. on Feb. 1, 2000, describes an adjustable propeller system. The system includes an outboard drive portion having a propeller. At least one linearly extendable and retractable trim arm is mounted between an outboard plate and the propeller to adjust the trim angle between the outboard plate and the propeller. An upper arm and a lower arm are each pivotally mounted to a transom mounting plate and typically mounted to the outboard mounting plate. The upper and lower arm are linearly extendable and retractable to adjust the depth of the outboard drive portion. 
     U.S. Pat. No. 6,383,043, which issued to Heston on May 7, 2002, describes a vertical trim system for marine outdrives. A vertical trim system for a marine inboard-outboard outdrive includes a transom plate and arms having first ends attached to the transom plate and second hands attached to a gimbal ring of the outdrive. 
     U.S. Pat. No. 5,934,955, which issued to Heston on Aug. 10, 1999, describes a vertical trim system for marine outdrives. The system, for a marine inboard-outboard outdrive, includes a transom plate defining an opening therethrough and having first and second sides, the first side adapted to be mounted to a boat transom. At least one arm includes first and second ends, the first end being pivotally coupled to the second side of the transom plate, such that the arm pivots about a horizontal axis. The second end of the arm is adapted to be pivotally coupled to a gimbal ring of an outdrive. 
     International Patent Application WO 94/00340, which was filed on Jun. 22, 1993, describes a boat propulsion unit comprising a suspension arrangement and a propeller drive shaft housing which, via a lower and an upper universal joint, are pivotally connected to each other. The suspension arrangement comprises a hollow frame member in the form of an extruded aluminum profile which is fixed around an opening in a boat transom, and a carrier attached to the frame member, said carrier covering the opening and supporting said pivot means. The frame member presents inlets and outlets for exhaust gases. 
     International Patent Application WO 99/22989, which was filed on Nov. 3, 1998, describes an omni-directional horizontal thrust adjustable marine propulsion system. The system is capable of providing independent control of propeller elevation, trim and steering utilizes a set of pivotally connected, independent frames. A pair of elevational hydraulic rams are connected between the vessel and the frame support for controlling the lift of the propeller. A trim hydraulic ram, coupled between the support frame and the upper gearcase controls the trim. Directional control is provided by a drive shaft coupled between the gear cases. 
     International Patent Application WO 91/19644, which was filed on Jun. 20, 1991, describes an arrangement in connection with a swingable turn-up inboard/outboard stern aggregate for a craft. An arrangement in a swingable turn-up inboard/outboard stern aggregate for a craft with an inboard engine and an outboard driving means comprises a screw, where the inboard driving shaft of the stern aggregate for connection with the engine is connected with a screw shaft which is approximately horizontal in a position for use and is mounted in the lower end of a housing by the aid of a transmission shaft, which is divided into two sections and surrounded by a housing. The first section is at one end mounted in the upper end of the housing and connected with the driving shaft, via a first universal joint, and is at its other end, via an angular gear, connected with an upper end of a section which is inclined rearwards and downwards. The lower end of the second section is connected with a screw shaft at a firm angle, via a transmission means of torsional moment. In connection with the angular gear comprising two sets of angular gear wheels, a reversing means is provided to reverse the direction of rotation of the lower section and, thus, the direction of movement of the craft. 
     The patents described above are hereby expressly incorporated by reference in the description of the present invention. 
     In certain types of marine propulsion systems, the U-joint is susceptible to wear and damage. Most known stern drive systems require the use of at least one U-joint in order to allow the system to move for the purpose of trimming or steering the drive unit relative to the transom of a boat. In addition, most known stern drive systems do not allow for the raising or lowering of a propeller shaft without a corresponding change in the trim of the drive. Typically, changing the elevation of the propeller shaft relative to the boat requires significant changes to the overall marine propulsion system. 
     It would therefore be significantly beneficial if a marine propulsion system could be provided which allows a stern drive unit to be raised or lowered without requiring a change in the trim angle of the drive unit. It would also be significantly beneficial if the stern drive unit could be provided which allows the propeller shaft to be steered about a steering axis which is coincident with the generally vertical drive shaft axis of rotation. 
     SUMMARY OF THE INVENTION 
     A marine propulsion system, made in accordance with a preferred embodiment of the present invention, comprises an input shaft which is connectable in torque transmitting relation with an engine. It also comprises a first intermediate shaft which is connected in torque transmitting relation with the input shaft and is rotatable about a first axis of rotation. It comprises a second intermediate shaft which is connected in torque transmitting relation with the first intermediate shaft and is rotatable about a second axis of rotation. The first and second axes of rotation of the first and second intermediate shafts are generally parallel to each other. The present invention further comprises a drive shaft which is connectable in torque transmitting relation with a second intermediate shaft. 
     In a particularly preferred embodiment of the present invention, it further comprises a propeller shaft connected in torque transmitting relation with the drive shaft. The input shaft is generally perpendicular to the first intermediate shaft. The present invention further comprises a first spur gear attached to the first intermediate shaft and a second spur gear attached to the second intermediate shaft. The first and second spur gears are connected in tooth meshing relation with each other. 
     A preferred embodiment of the present invention further comprises a first bevel gear connected in torque transmitting relation with the second intermediate shaft to rotate in a first direction and a second bevel gear connected in torque transmitting relation with a second intermediate shaft to rotate in a second direction. It further comprises a clutch which is moveable between a first position to cause the drive shaft to rotate in a first direction and a second position to cause the drive shaft to rotate in a second direction. The first bevel gear is connected in torque transmitting relation with the drive shaft when the clutch is in the first position and the second bevel gear is connected in torque transmitting relation with the drive shaft when the clutch is in the second position. The clutch is connected in torque transmitting relation with the drive shaft by a plurality of splines formed on the clutch and on the drive shaft. 
     A preferred embodiment of the present invention further comprises a drive shaft bevel gear attached to the drive shaft and a propeller shaft bevel gear attached to the propeller shaft. The drive shaft bevel gear is disposed in tooth meshing relation with the propeller shaft bevel gear. 
     A preferred embodiment of the present invention further comprises a transom housing which is attachable to a transom of a marine vessel. The input shaft is supported for rotation about an input shaft axis of rotation by the transom housing. A drive shaft housing is also provided. The drive shaft and the first and second bevel gears are supported for rotation about the drive shaft axis of rotation by the drive shaft housing. The present invention also comprises an intermediate housing. The first and second intermediate shafts are supported for rotation about the first and second axes of rotation by the intermediate housing. 
     The present invention further comprises a first hydraulic cylinder connected between the drive shaft housing and the intermediate housing. A gearcase is also provided. The propeller shaft is supported for rotation about a propeller shaft axis of rotation by the gearcase and the propeller shaft bevel gear is supported for rotation about the drive shaft axis of rotation by the gearcase. The present invention further comprises a hydraulic actuator connected between the drive shaft housing and the gearcase for causing the gearcase to rotate about the drive shaft axis of rotation. A second hydraulic cylinder is connected between the transom housing and the intermediate housing. The intermediate housing is rotatable relative to the transom housing and the drive shaft housing is rotatable relative to the intermediate housing. 
     An embodiment of the marine propulsion system made in accordance with the present invention can comprise an input shaft which is connectable in torque transmitting relation with an engine, a drive shaft which is connectable in torque transmitting relation with the input shaft, and a propeller shaft connectable in torque transmitting relation with the drive shaft. The propeller shaft is rotatable about a drive shaft axis of rotation. The drive shaft is supported for rotation about the drive shaft axis of rotation by a drive shaft housing. The propeller shaft is supported for rotation about a propeller shaft axis of rotation by a gearcase, wherein the gearcase is rotatable about the drive shaft axis of rotation relative to the drive shaft housing. A hydraulic actuator is connected between the drive shaft housing and the gearcase for causing the gearcase to rotate about the drive shaft axis of rotation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be more fully and completely understood from a reading of the description of the preferred embodiment in conjunction with the drawings, in which: 
         FIG. 1  shows the relative positions of the shafts, gears, and clutch of the present invention; 
         FIG. 2  is a side section view of a preferred embodiment of the present invention; 
         FIG. 3  is similar to  FIG. 2  but with the gearcase raised; 
         FIG. 4  shows the gearcase lowered in comparison to  FIG. 3 ; 
         FIG. 5  shows the gearcase trimmed to place the drive shaft angle at a non-perpendicular angle relative to a horizontal plane; and 
         FIG. 6  shows the marine propulsion system tilted upward as it would be during storing or moving the marine vessel. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Throughout the description of the preferred embodiment of the present invention, like components will be identified by like reference numerals. 
       FIG. 1  is a highly simplified isometric representation of the basic concept of the present invention, but with only the shafts, gears, and clutch being shown. The other components of the present invention will be illustrated and described in detail below, but  FIG. 1  is intended to simplify the explanation of the basic operation of the present invention. 
     As illustrated in  FIG. 1 , a marine propulsion system made in accordance with the present invention comprises an input shaft  10  which is connectable in torque transmitting relation with an internal combustion engine. A first intermediate shaft  12  is connected in torque transmitting relation with the input shaft  10  and is rotatable about a first axis of rotation  14 . A second intermediate shaft  18  is connected in torque transmitting relation with the first intermediate shaft  12  and is rotatable about a second axis of rotation  20 . The first and second axes of rotation,  14  and  20 , are generally parallel to each other in a preferred embodiment. A drive shaft  24  is connectable in torque transmitting relation with the second intermediate shaft  18 . A propeller shaft  28  is connected in torque transmitting relation with the drive shaft  24 . In a particularly preferred embodiment of the present invention, the input shaft  10  is generally perpendicular to the first intermediate shaft  12 . 
     A first spur gear  30  is attached to the first intermediate shaft  12  and a second spur gear  32  is attached to the second intermediate shaft  18 . The first and second spur gears,  30  and  32 , are connected in tooth meshing relation with each other. A first bevel gear  40  is connected in torque transmitting relation with the second intermediate shaft  18  to rotate in a first direction. A second bevel gear  42  is connected in torque transmitting relation with the second intermediate shaft  18  to rotate in a second direction. In a preferred embodiment, the first and second bevel gears,  40  and  42 , are connected in tooth meshing relation with a bevel gear  46  that is attached to the second intermediate shaft  18 . This bevel gear  46  and the first and second bevel gears,  40  and  42 , are in constant rotation as long as the second intermediate shaft  18  is rotating about its axis of rotation  20 . A clutch  50 , which is illustrated as a cone clutch, is moveable between a first position to cause the drive shaft  24  to rotate in a first direction and a second position to cause the drive shaft  24  to rotate in a second direction. In a preferred embodiment, the clutch  50  is a cone clutch that can move into frictional driving relation with either the first bevel gear  40  or the second bevel gear  42 . The clutch  50  is connected in torque transmitting relation with the drive shaft  24  by a plurality of spline teeth that transmits torque between the clutch  50  and the drive shaft  24 . When the clutch  50  is moved upwardly into frictional driving relation with the first bevel gear  40 , the drive shaft  24  rotates in the first direction along with the first bevel gear  40 . Conversely, when the clutch  50  is moved downwardly into frictional driving relation with the second bevel gear  42 , the drive shaft  24  moves in the second direction along with the second bevel gear  42 . When the clutch  50  is in a central position, the drive shaft  24  is not rotated because of the lack of frictional driving relationship between the clutch  50  and either the first or second bevel gears,  40  or  42 . The first bevel gear  40  is connected in torque transmitting relation with the drive shaft  24  when the clutch  50  is in the first position and the second bevel gear  42  is connected in torque transmitting relation with the drive shaft  24  when the clutch is in the second position. 
     Another significant advantage of the present invention relates to the first and second spur gears,  30  and  32 , which are connected in tooth meshing relation with each other. These spur gears can be interchanged with other spur gears having different gear tooth ratios. As a result, the gear ratio of the entire system can be quickly and easily changed. Known systems require significant disassembly and reassembly to accomplish a gear ratio change. 
     The present invention further comprises a drive shaft bevel gear  60  which is attached to the drive shaft  24  and a propeller shaft bevel gear  62  which is attached to the propeller shaft  28 . The drive shaft bevel gear  60  is disposed in tooth meshing relation with the propeller shaft bevel gear  62  in order to cause the propeller shaft  28  to rotate in a first or second direction in coordination with the drive shaft  24 . 
       FIG. 2  is a side view which is sectioned to show some of the internal components of the present invention. Some of the components described above in conjunction with  FIG. 1  are also visible in  FIG. 2 . They are identified by the same reference numerals used above in order to allow  FIG. 1  to be compared to  FIG. 2 .  FIG. 2  also shows a transom housing  70  which is attachable to a transom of a marine vessel. The input shaft  10  is supported for rotation about an input shaft axis  72 . A drive shaft housing  76  is provided. The drive shaft  24  and the first and second bevel gears,  40  and  42 , are supported for rotation about a drive shaft axis  80  by the drive shaft housing  76 . It should be understood that the drive shaft  24  can be constructed of two pieces that are connectable to each other with a spline connection in order to make assembly and disassembly of the marine propulsion system easier. A lower portion of the drive shaft  24  extends downwardly toward the drive shaft bevel gear  60  and the upper portion of the drive shaft  24  extends toward the first and second bevel gears,  40  and  42 . An intermediate housing  84  is also provided. The first and second intermediate shafts,  12  and  18 , are supported for rotation about the first and second axes,  14  and  20 , by the intermediate housing  84 . With continued reference to  FIG. 2 , a first hydraulic cylinder  90  is connected between the drive shaft housing  76  and the intermediate housing  84 . These connection points are identified by reference numerals  91  and  92 , respectively, in  FIG. 2 . 
     A gearcase  94  is also provided. The propeller shaft  28  is supported for rotation about the propeller shaft axis of rotation  96  by the gearcase  94  and the propeller shaft bevel gear  62  is supported for rotation about the drive shaft axis  80 . As will be described in greater detail below, the gearcase  94  is rotatable about axis  80  relative to the drive shaft housing  76 . A hydraulic actuator  100  is connected between the drive shaft housing  76  and the gearcase  94  for causing the gearcase  94  to rotate about the drive shaft axis  80 . 
     With continued reference to  FIGS. 1 and 2 , several important advantageous characteristics of the present invention can be seen. Because of the fact that torque is transmitted between the input shaft  10  and the first intermediate shaft  12 , the intermediate housing  84  is rotatable about the axis  14  of the first intermediate shaft  12  relative to the transom housing  70 . In addition, because of the relationship of the bevel gear  46  and the first and second bevel gears  40  and  42 , the drive shaft housing  76  is rotatable about axis  20  of the second intermediate shaft  18  relative to the intermediate housing  84 . The combination of these two axes of rotation,  14  and  20 , with respect to the transom housing  70 , the intermediate housing  84 , and the drive shaft housing  76  provides a significant advantage because it allows the propeller shaft  28  to be raised or lowered without having to change the trim angle of the drive shaft  24 . 
     With continued reference to  FIG. 2 , a second hydraulic cylinder  110  is connected between the transom housing  70  and the intermediate housing  84 . The combined use of the first hydraulic cylinder  90  and the second hydraulic cylinder  110  allows the drive unit to be rotated about axis  14 , axis  20 , or both axes simultaneously. The second hydraulic cylinder is connected between the points identified by reference numerals  114  and  116 . 
       FIG. 3  shows a drive unit after the intermediate housing  84  has been rotated clockwise relative to the transom housing  70  and the drive shaft housing  76  has been rotated counterclockwise by a similar magnitude, relative to the intermediate housing  84 . This is accomplished by selective actuation of the first and second hydraulic cylinders,  90  and  110 . It should be noted that the drive shaft  24  remains generally vertical, but the propeller shaft  28  is raised by the difference in height between the axes of rotation,  14  and  20 , of the first and second intermediate shafts,  12  and  18 . 
       FIG. 4  shows the device described above in conjunction with  FIGS. 2 and 3 , but with the intermediate housing  84  rotated slightly about the centerline  14  of the first intermediate shaft  12  with a corresponding clockwise rotation of the drive shaft  76  relative to the intermediate shaft  14 , about the centerline  20  of the second intermediate shaft  18 . This lowers the position of the propeller shaft  28  while maintaining the drive shaft  24  in a generally vertical position. The slight lowering of the gearcase  94  can be seen by comparing the position of the second intermediate shaft  18  relative to axis  72  of the input shaft  10 , which remains stationary during the trimming maneuver. 
     With reference to  FIGS. 3 and 4 , it can be seen that a raising maneuver as illustrated in  FIG. 3  results in a slightly forward movement of the gearcase  94  toward the marine vessel to which it is attached. Similarly, a lowering of the gearcase  94  as described above in conjunction with  FIG. 4  also results in a movement of the gearcase  94  toward the marine vessel. This results from the fact that the distance between the axes of rotation,  14  and  20 , decreases, when measured along a horizontal plane, during both maneuvers. The maximum horizontal distance between axes  14  and  20  occurs when these two axes of rotation, or the first and second intermediate shafts,  12  and  18 , are within the same horizontal plane. This is illustrated in  FIG. 2 . 
       FIG. 5  illustrates the use of the present invention to provide a trim angle with regard to the position of the drive shaft  24 . The gearcase  94  is trimmed outwardly away from the marine vessel. This places the axis  96  of the propeller shaft  28  in a non-horizontal position as illustrated (i.e. not parallel to axis  72  of the input shaft  10 ). This is accomplished by rotating the intermediate housing  84  clockwise about the axis  14  of the first intermediate shaft  12  with little or no corresponding rotation of the drive shaft  76  relative to the intermediate housing  84 . 
       FIG. 6  shows a more extreme change in the position of the gearcase  94 , when compared to  FIG. 5 . This position is accomplished by rotating the intermediate housing  84  in a clockwise direction about axis  14  of the first intermediate shaft  12  relative to the transom housing  70  while simultaneously rotating the drive shaft housing  76  in a clockwise direction about axis  20  of the second intermediate shaft  18 . As described above, these two simultaneous rotations are accomplished by the first and second hydraulic cylinders,  90  and  110 . It should be understood that the drive unit could be tilted upward even farther than illustrated as long as the intermediate housing is provided with sufficient clearance to allow this to occur. Since the system has no U-joint, there can be no limitation caused by the U-joint as with normal drive systems. This could allow the propeller to be changed while the boat is in the water. Also, the drive can be tilted upward sufficiently to lift the system out of salt water, thus minimizing corrosion. 
     With continued reference to  FIG. 6 , it can be seen that the first hydraulic cylinder  90  exerts a force between points  91  and  92  to rotate the drive shaft housing  76  relative to the intermediate housing  84 . The second hydraulic cylinder  110  exerts a force between points  114  and  116  to rotate the intermediate housing  84  relative to the transom housing  70 . 
     The relative positions of the various housings illustrated in  FIGS. 2–6  show only a few of the many potential positions of the intermediate housing  84  and drive shaft housing  76  relative to the transom housing  70  and relative to each other. In this way, the gearcase  94  can be trimmed outwardly or inwardly, with a corresponding change in the angle of the axis of rotation  80  of the drive shaft  24 . In addition, the gearcase  94  can be moved upwardly or downwardly without changing the angle of axis  80  to a horizontal plane. This allows a trim angle to be maintained while the gearcase  94  is moved upwardly or downwardly relative to the transom housing  70 . 
     With continued to reference to  FIGS. 2–6 , it can be seen that actuation of the hydraulic actuator  100  can be used to cause the gearcase  94  to rotate about the drive shaft axis  80  in either a clockwise or counterclockwise direction to change the steering angle of the propeller shaft  28 . When this occurs, the propeller shaft  28  and the propeller shaft bevel gear  62  rotate about the axis of rotation  80 . As a result, the steering axis of the marine propulsion system remains perpendicular to the propeller shaft axis of rotation  96  and in intersecting relation with the propeller shaft  28 . 
     With reference to  FIGS. 1–6 , it can be seen that a marine propulsion system made in accordance with the present invention comprises an input shaft  10  which is connectable in torque transmitting relation with an engine. It also comprises a first intermediate shaft  12  which is connected in torque transmitting relation with the input shaft  10  and is rotatable about a first axis of rotation  14 . A second intermediate shaft  18  is connected in torque transmitting relation with the first intermediate shaft  12  and is rotatable about a second axis of rotation  20 . As particularly illustrated in  FIG. 1 , the first and second axes of rotation are generally parallel to each other in a preferred embodiment of the present invention. A drive shaft  24  is connectable in torque transmitting relation with the second intermediate shaft  18 . A propeller shaft  28  is connected in torque transmitting relation with the drive shaft  24 . The input shaft  10  is generally perpendicular to the first intermediate shaft  12 . The first and second spur gears,  30  and  32 , are attached to the first and second intermediate shafts,  12  and  18 , and are connected in tooth meshing relation with each other. A first bevel gear  40  is connected in torque transmitting relation with the second intermediate shaft  18 , through the operation of bevel gear  46 , and a second bevel gear  42  is connected in torque transmitting relation with the second intermediate shaft  18  through the operation of the bevel gear  46 . A clutch  50  is moveable between a first position to cause the drive shaft  24  to rotate in a first direction and a second position to cause the drive shaft  24  to rotate in a second direction. The first bevel gear  40  is connected in torque transmitting relation with the drive shaft  24  when the clutch  50  is in the first position and the second bevel gear  42  is connected in torque transmitting relation with the drive shaft  24  when the clutch  50  is in the second position. The clutch is connected in torque transmitting relation with the drive shaft  24  by a plurality of splines that are formed on the clutch and on the drive shaft. A drive shaft bevel gear  60  is attached to the drive shaft  24  and the propeller shaft bevel gear  62  is attached to the propeller shaft  28 . These two bevel gears are disposed in tooth meshing relation with each other. 
     With continued reference to  FIGS. 1–6 , a transom housing  70  is attachable to a transom of a marine vessel and the input shaft  10  is supported for rotation about an input shaft axis of rotation  72  by the transom housing  70 . A drive shaft housing  76  is provided to support the drive shaft  24  and the first and second bevel gears,  40  and  42 , for rotation about the drive shaft axis  80 . An intermediate housing  84  is provided to support the first and second intermediate shafts,  12  and  18 , for rotation about the first and second axes,  14  and  20 . A first hydraulic cylinder  90  is connected between the drive shaft housing  76  and the intermediate housing  84 . A gearcase  94  is provided and the propeller shaft  28  is supported for rotation about a propeller shaft axis of rotation  96  by the gearcase  94 . The propeller shaft bevel gear  62  is supported for rotation about both the propeller shaft axis  96  and the drive shaft axis  80 . A hydraulic actuator  100  is connected between the drive shaft housing  76  and the gearcase  94  for causing the gearcase  94  to rotate about the drive shaft axis of rotation  80 . A second hydraulic cylinder  110  is connected between the transom housing  70  and the intermediate housing  84 . The intermediate housing  84  is rotatable relative to the transom housing  70  and the drive shaft housing  76  is rotatable relative to the intermediate housing  84 . 
     With continued reference to  FIGS. 1–6 , it can be seen that one of the primary advantages of the present invention is that the axes of rotation of the various housings relative to each other are coincident with axes of shafts that are used to transmit torque from the input shaft  10  to the propeller shaft  28 . This eliminates the need for the use of U-joints and also allows the gearcase  94  to be raised or lowered without the necessity of the axis  80  being moved away from its current trim angle. 
     Although the present invention has been described with particular specificity and illustrated to show a particularly preferred embodiment, it should be understood that alternative embodiments are also within its scope.