Abstract:
A connection system for connecting two or more marine propulsion devices together provides a coupler that can be rotated in place, without detachment from other components, to adjust the distances between the tie bar arms. In addition, the use of various clevis ends and pairs of attachment plates on the components significantly reduces the possibility of creating moments when forces and their reactions occur between the various components.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is generally related to a connection system for connecting two or more marine propulsion devices together and, more particularly, to a system that simplifies and strengthens a tie bar system for operating two or more outboard motors in tandem. 
     2. Description of the Prior Art 
     It is well known by those skilled in the art that two or more marine propulsion devices can be used in tandem on a marine vessel. When two or more outboard motors are used in this manner, a tie bar or connecting link is used to connect the outboard motors together so that they can be steered in tandem to allow the marine vessel to be maneuvered with both marine propulsion devices operating cooperatively. 
     U.S. Pat. No. 6,406,340, which issued to Fetchko et al. on Jun. 18, 2002, describes a twin outboard motor hydraulic steering system. The steering assembly applies a force to tiller arms of twin marine, outboard propulsion units and rotates the propulsion units about a steering axis between a center position and hard over positions to each side of the center position. Each propulsion unit is supported for arcuate movement about a tilt axis which is generally perpendicular to the steering axis. There is a hydraulic steering apparatus mounted on a first of the propulsion units which includes a hydraulic cylinder pivotally connected to a member which is pivotally mounted on the tiller arm of the first propulsion unit. A tie bar is pivotally connected to the steering apparatus and pivotally connected to the tiller arm of a second propulsion unit. For example, the tie bar may be pivotally connected to the steering apparatus by a ball joint connected to the steering apparatus by a bracket which moves with the member. 
     U.S. Pat. No. 4,836,812, which issued to Griffiths on Jun. 6, 1989, discloses a steering system for an auxiliary marine engine. The steering system for controlling an auxiliary marine engine includes an auxiliary engine steering cable operably connected to the hydraulic cylinder of the steering system for the primary engine so that linear movement of the hydraulic cylinder results in movement of the steering cable and pivotal steering of the auxiliary engine. 
     U.S. Pat. No. 4,731,035, which issued to Wagner on Mar. 15, 1988, describes a steering mechanism for outboard motors. The mechanism is disclosed for a boat equipped with an outboard motor. The steering mechanism has a pair of opposed single acting cylinders maintained in a spaced relationship by a frame member. A pair of brackets enables pivotal connection of the steering mechanism with the mounting bracket of the motor. A piston is received in and extends between the cylinders and carries a lost motion linkage connectable with the tiller arm of the motor to induce steering movement of the motor upon actuation of the piston. 
     U.S. Pat. No. 6,561,860, which issued to Colyvas on May 13, 2003, describes a maneuvering enhancer for twin outboard motor boats. An adjustable length bar is used to replace the rigid bar, the one connecting the two outboards or the two outdrives of a boat, for steering purposes. The adjustable bar is electrically operated through a switch on the boat&#39;s dashboard, the switch having two operating positions. One position is to keep propellers creating two parallel thrusts and a second position is to shift the propellers to create a vee configuration, by which the boat&#39;s maneuverability will be enhanced. 
     U.S. Pat. No. 4,009,678, which issued to North on Mar. 1, 1977, discloses a multiple push-pull cable transmission apparatus. A racing boat is powered by a pair of pendent inboard-outboard drive units having inboard steering arms. A pair of push-pull cable units connect a forward located steering wheel unit to the arms. The cable units extend along opposite sides of the boat with the casing fixed at the steering wheel and the core wires secured to the opposite sides of the steering wheel and to the opposite steering arms. A power steering unit coupled to the one steering arm has an input element. The adjacent cable unit has a threaded extension pipe with a fixed coupler connected to the power control input. A core rod is connected to the core and is slidably mounted in the pipe and is pivotally connected to the power steering link to transmit casing reaction forces to the power input. An adjustable rigid linkage includes a tie rod having adjustable ends pivotally connected to the anchor member on the extension pipes. The anchor member of the second cable unit is slidably mounted in a pivotally mounted support for generally linear movement. The rod directly interconnects the two anchor members to each other and to the power input for rapid power steering response. A second adjustable tie rod is pivotally connected to the arms and the core wires and is set to properly locate the steering arms. 
     The patents described above are hereby expressly incorporated by reference in the description of the present invention. 
     Known tie bar systems for tandem steering of two or more outboard motors typically exhibit two inherent problems. First, adjusting the various elements of the system during installation can be exceedingly difficult when using known tie bar systems. In addition, the structure of the individual joints, about which the various linkages rotate, can place the components under undue stress because of the lack of alignment between certain forces and their reactions. It would therefore be significantly beneficial if a tandem outboard motor steering system could be provided which is easier to assemble and adjust than known systems and which directs reactive forces in alignment with original forces to avoid creating moments that can otherwise be destructive to individual components. 
     SUMMARY OF THE INVENTION 
     A connection system for connecting two marine propulsion devices together, in a preferred embodiment of the present invention, comprises a first tie bar arm, which is attachable to a first one of the two marine propulsion devices, and a first connecting link which is pivotally connectable to the first tie bar arm for rotation about a first axis. It also comprises a first rod assembly which is pivotally connectable to the first connecting link for rotation about a second axis and a coupler which is attachable in a first direction of threaded association with the rod assembly. It further comprises a second rod assembly which is attachable in a second direction of threaded association with the coupler. The first and second directions of threaded association are opposite to each other. 
     The present invention further comprises a second connecting link which is pivotally connectable to the second rod assembly for rotation about a third axis. A preferred embodiment of the present invention further comprises a second tie bar arm which is attachable to a second one of the two marine propulsion devices. The second tie bar arm is pivotally connectable to the second connecting link for rotation about a fourth axis. 
     The first tie bar arm can comprise a first attachment plate and a second attachment plate. The first and second attachment plates are generally parallel to each other. The first connecting link is disposable between the first and second attachment plates. The first axis extends through the first and second attachment plates and also through the first connecting link. 
     The first connecting link comprises a first clevis end. The first rod assembly is disposed within the first clevis end. The second axis extends through the first rod assembly and through the first clevis end. In one embodiment of the present invention, the first connecting link comprises a second clevis end which is disposed between the first and second attachment plates. The first axis extends through the first and second attachment plates and through the second clevis end. The second clevis end is shaped to receive an extension portion of a third connecting link. The first and second axes extend in directions which are perpendicular to each other and these first and second axes are associated in nonintersecting relation with each other in a preferred embodiment. 
     The first direction of threaded association employs a right handed thread and the second direction of threaded association employs a left handed thread. As a result, the first and second rod assemblies are moved toward each other in response to rotation of the coupler in a first rotational direction about its central axis and the first and second rod assemblies are moved away from each other in response to rotation of the coupler in a second rotational direction about its central axis. The first and second rotational directions are opposite to each other. 
     The present invention can further comprise a bolt extending through the first tie bar arm and through the first connecting link coaxially with the first axis. The bolt can be a shoulder bolt which is sized to retain the first connecting link in an uncompressed state between the first and second attachment plates. At least one flanged radial bearing is disposed around the bolt and between the first and second attachment plates. The present invention can further comprise a non-flanged radial bearing disposed around the bolt and between the first and second attachment plates. 
     As a result of the present invention, a first resultant force exerted by the first connecting link on the first tie bar arm is symmetrical with a second resultant force exerted by the first tie bar arm on the first connecting link. The first and second resultant forces, which comprise an original force and a reactive force, are generally equal in magnitude and directed in opposite directions along a common axis. The first and second resultant forces combine to create approximately no net moment about any point. 
    
    
     
       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: 
         FIGS. 1–3  illustrate the components and assembly of a prior art connection system; 
         FIG. 4  is an isometric view showing the present invention used to connect two outboard motors together; 
         FIG. 5  shows the present invention used in a manner which connects three outboard motors together; 
         FIGS. 6 and 7  are section views of the present invention shown in  FIG. 4 ; 
         FIGS. 8 and 9  are section views of the present invention as shown in  FIG. 6 ; 
         FIG. 10  is an isometric view showing a central outboard motor connection of the present invention when it is used to connect three outboard motors together; 
         FIG. 11  is an isometric view similar to  FIG. 10 , but also showing a pedestal and mounting cradle of an outboard motor; and 
         FIG. 12  is a section view of a tie bar arm when it is used as a central point of the present invention for connecting three outboard motors together. 
     
    
    
     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. 
     In order to fully understand and appreciate the advantages provided by the present invention, it is necessary to first understand the current types of tie bar systems that are known to those skilled in the art.  FIG. 1  shows a known assembly of components that is used to tie two outboard motors together. The assembly of components comprises two threaded steering rods  10  that are each provided with an opening  12  that can have a ball joint disposed therein. A locking nut  14  is provided. A coupler  18  is threaded at both ends,  19 , so that either of the two threaded steering rods  10  can be attached to the coupler  18  in threaded association, one at each end  19 . Bolts  20 , washers  22  and nuts  23  are provided to attach the openings  12  of the threaded steering rods  10  to openings in steering arms of the outboard motors. Two flexible tubes  26  are used in conjunction with the coupler  18  and the threaded steering rods  10  in a manner that will be described below in conjunction with  FIG. 2 . 
       FIG. 2  shows the components of  FIG. 1  attached to two steering arms  30 . Although not shown in  FIG. 2 , it should be understood that the steering arms  30  are attached to the outboard motors so that the arms can be used to cause the outboard motors to rotate about their respective steering axes. 
     In the assembly shown in  FIG. 2 , the threaded steering rods  10  are threaded into the ends  19  of the coupler  18 . The locking nut  14  is used to prevent rotation of the coupler  18  relative to the threaded rods  10 . The flexible tubes  26  are disposed over the ends  19  of the coupler  18 , the threaded ends of the threaded arms  10 , and the locking nut  14 . Also shown in  FIG. 2  is a steering drag link  34  which is attached to one of the two steering arms  30  to cause them to rotate about their respective steering axes. Although not shown in  FIG. 2 , the steering drag link  34  would typically be connected to a push-pull cable to allow the operator to cause the attached steering arm  30  to rotate. The connection between the two steering arms  30 , provided by the coupler  18 , the threaded steering rods  10 , and the bolts  20  caused the two steering arms  30  to move in tandem with each other. 
       FIG. 3  is an end view of the apparatus shown in  FIG. 2 . The items in  FIG. 3  are identified by the same reference numerals used to identify them in  FIGS. 1 and 2 . As can be seen in  FIG. 3 , the force F of the threaded bar  10  on the bolt  20  creates a reactive force R by the steering arms  30  on the bolt  20 . As illustrated in  FIG. 3 , the force F and the reactive force R are not aligned with each other in a coaxial manner. Instead, they are offset because of the physical relationship between the hole  12  of the threaded bar  10  and the hole extending through the steering arm  30 . Because of this offset, forces F and reactive forces R cause a moment to exist about a point that is generally located within the structure of the bolt  20  and between the hole  12  and the threaded rod  10  and the hole in the steering arm  30 . This moment can cause stress and significant damage over time. 
     With continued reference to  FIGS. 1–3 , it can also be seen that the assemblage of parts shown in  FIG. 1  necessitate a potentially complex procedure to assemble the parts and align the two steering arms  30  in parallel association with each other. When the two threaded rods  10  are threaded into the ends  19  of the coupler  18 , their two openings  12 , in which ball joints are typically provided, are spaced apart by a defined distance. If this defined distance is precisely equal to the distance between the associated holes in the steering arms  30 , the bolts  20  can be used to make the assembly shown in  FIG. 2 . However, if the holes  12  are not spaced apart by the same distance as the holes in the steering arms  30  when the two steering arms are perfectly parallel with each other, an adjustment has to be made. This adjustment is accomplished by rotating one or both of the threaded rods  10  relative to the coupler  18 . This rotation, in turn, requires that the bolts  20  be removed to allow this rotation. If the adjustment is not satisfactory to connect the two steering arms  30  together while in perfectly parallel association with each other, the bolts  20  must again be removed and one or both of the threaded rods  10  must be rotated relative to the coupler  18  to adjust the distance between the holes  12 . These steps must continue until the distance between the holes  12  in  FIG. 2  equal the distance between the holes in the steering arms  30  when the steering arms  30  are parallel to each other. 
     With continued reference to  FIGS. 1–3 , it should be understood that the locking nut  14  is required in order to prevent the coupler  18  from moving toward one or the other of the steering arm  30  by rotating about its own axis. Since known systems use right hand threads on both threaded rods  10  and both ends  19  of the coupler  18 , rotation of the coupler  18  about its central axis, even after attached to the threaded rods  10  is illustrated in  FIG. 2 , will cause the coupler to move either left or right in  FIG. 2  and possibly to detach from one of the two threaded rods  10 . Therefore, the locking nut  14  is jammed against one end of the coupler  18  to prevent rotation of the coupler  18 . 
     With continued reference to  FIGS. 1–3 , it can be seen that the known type of tie bar arrangement, which is generally known to those skilled in the art and currently used in most applications, presents a cumbersome method for adjusting the distance between the holes  12  of the threaded rods  10  and, in addition, allows a moment to exist because of the offset between the force F and the reaction force R. 
       FIG. 4  shows the present invention used to connect two outboard motors in tandem with each other. Reference numerals  41  and  42  represent two rotatable elements that are part of two outboard motors. For clarity, the entire outboard motors are not shown. Steering axes  45  and  46  are the two steering axes of the two outboard motors, respectively. A first tie bar arm  51  is attachable to a first one of the two marine propulsion devices, or outboard motors. A first connecting link  61  is pivotally connectable to the first tie bar arm  51  for rotation about a first axis  71  relative to the first tie bar arm  51 . A first rod assembly  81  is pivotally connectable to the first connecting link  61  for rotation about a second axis  91 . A coupler  100  is attachable in a first direction of threaded association with the first rod assembly  81 . A second rod assembly  82  is attachable in a second direction of threaded association with the coupler  100 . The first and second directions of threaded association are opposite to each other. These two directions of threaded association are identified by arrows T 1  and T 2  in  FIG. 4 . 
     With continued reference to  FIG. 4 , a second connecting link  62  is pivotally connectable to the second rod assembly  82  for rotation about a third axis  73 . A second tie bar arm  52  is attachable to a second one of the two marine propulsion devices. The second tie bar arm  52  is pivotally connectable to the second connecting link  62  for rotation about a fourth axis  74 . 
     With continued reference to  FIG. 4 , the first tie bar arm  51  comprises a first attachment plate  91  and a second attachment plate  92 . The first and second attachment plates,  91  and  92 , are generally parallel to each other. The first connecting link  61  is disposable between the first and second attachment plates,  91  and  92 . The first axis  71  extends through the first and second attachment plates,  91  and  92 , and through the first connecting link  61 . The first connecting link  61  comprises a first clevis end  96 . The first rod assembly  81  is disposed within the first clevis end  96 . The second axis  72  extends through the first rod assembly  81  and through the first clevis end  96 . 
     With continued reference to  FIG. 4 , it can be seen that rotation of the coupler  100  in the direction identified as R 1  will cause the first and second connecting links,  61  and  62 , to be drawn toward each other because of the different threads at the two ends of the coupler  100  and the different threads on the first and second rod assemblies,  81  and  82 . Conversely, rotation of the coupler  100  in the direction identified as R 2  in  FIG. 4  will cause the first and second connecting links,  61  and  62 , to move apart. By selective rotation of the coupler  100 , the precise distance between the first and fourth axes of rotation,  71  and  74 , can be accurately determined. Locking nuts,  111  and  112 , are used to prevent inadvertent rotation of the coupler  100  relative to the first and second rod assemblies,  81  and  82 . 
       FIG. 5  is generally similar to  FIG. 4 , except that it shows a slightly different embodiment of the present invention which is intended for use when three or more marine propulsion devices are used in tandem. It should me understood that, if three or more outboard motors are used in tandem, the arrangement shown in  FIG. 5  is repeated as many times as are required. The first and second tie bar arms,  51  and  52 , are identical to those described above in conjunction with  FIG. 4 . The difference in the embodiment shown in  FIG. 5  is that the first connecting link  61 ′ is formed differently than the first connecting link  61  described above in conjunction with  FIG. 4 . The first connecting link  61 ′ in  FIG. 5  comprises a second clevis end  97  which is disposed between the first and second attachment plates,  91  and  92 . The first axis  71  extends through the first and second attachment plates,  91  and  92 , and through the second clevis end  97  of the first connecting link  61 ′. The second clevis end  97  is shaped to receive an extension portion  120  of a third connecting link  63 . The remaining components to the left of the third connecting link  63  are similar to the components described above in conjunction with  FIGS. 4 and 5  and which are located between the first and second connecting links  61  and  62 . As illustrated in  FIG. 5 , these components would comprise a third rod assembly  83  and another coupler that is similar to the coupler identified by reference numeral  100  in  FIG. 5 . 
       FIG. 6  is a section view of the first tie bar arm  41 , the first connecting link  61 , and the first rod assembly  81  with associated components which include the coupler  100 .  FIG. 7  is a section view taken through the first rod assembly  81  and first connecting link  61  as shown. 
     With reference to  FIGS. 6 and 7 , the relationship between the first connecting link  61  and the first and second axes,  71  and  72 , can be seen. In addition, the first clevis end  96  illustrates its relationship to both the first rod assembly  81  and the second axis  72 . In addition, it can be seen that the first connecting link  61  is disposed between the first and second attachment plates,  91  and  92 , of the first tie bar arm  51 . 
     In  FIGS. 6 and 7 , it can also be seen that the first and second axes,  71  and  72 , are generally perpendicular to each other and are arranged in nonintersecting association with each other. The locking nut  111  is shown in its relationship to both the coupler  100  and the first rod assembly  81 .  FIGS. 6 and 7  show the application of the present invention in conjunction with an outboard motor that is connected in tandem with another outboard motor (not shown in  FIGS. 6 and 7 ). 
       FIG. 8  is a section view of a first tie bar arm  51 .  FIG. 9  is a section view of  FIG. 8  as shown. The primary differences between  FIGS. 8 and 9 , compared to  FIGS. 6 and 7 , relate to the fact that the first connecting link  61 ′ is provided with both first and second clevis ends,  96  and  97 , respectively. These can be seen by viewing  FIGS. 8 and 9  together. The provision of the second clevis end  97  allows the extension portion  120  of the third connecting link  63  to be disposed within the second clevis end  97  to allow the combined connection of the first and second connecting links,  61 ′ and  63 , to be connected as shown in  FIGS. 8 and 9  for rotation about axis  71 . 
     The arrangement shown in  FIGS. 8 and 9  represents the type of connection shown in  FIG. 5 , wherein three or more outboard motors are connected to each other. As an example, the first tie bar arm  51  in  FIGS. 5 ,  8 , and  9  represents the center outboard motors located between two other outboard motors and connected to those two outboard motors with couplers  100  as described above. In order to facilitate this connection of two other outboard motors to the one to which the first tie bar arm  51  is attached, the first connecting link  61 ′ is configured with a second clevis end  97  that allows the extension portion  120  of a third connecting link  63  to be connected in combination with the first connecting link  61  and the first and second attachment plates,  91  and  92 , as shown in  FIG. 9  for common rotation about the first axis  71 . 
       FIG. 10  is an isometric view of the first tie bar arm  51  associated with the first connecting link  61 ′ and the third connecting link  63 .  FIG. 10  shows the relationship between the second clevis end  97  of the first connecting link  61 ′ and the extension portion  120  of the third connecting link  63 . The first and third connecting links,  61 ′ and  63 , allow the first and third rod assemblies,  81  and  83 , to rotate independently about the first axis  71  while remaining attached to the first and second attachment plates,  91  and  92 , of the first tie bar arm  51 . The other components identified in  FIG. 10  are described above and will not be described again in conjunction with  FIG. 10 . 
       FIG. 11  is an isometric view of the first tie bar arm  51  attached to a steering head of an outboard motor. The steering head is connected to the mounting cradle  200  of an engine of the outboard motor with a pin attaching it to the mounting cradle. The outboard motor is supported by a support plate attached to the mounting cradle  200  and supported by resilient mounts, such as those identified by reference numeral  202 . A pedestal  210  is attachable to a transom of a marine vessel, with surfaces  214  and  216  being disposed in contact with the rearward surface of the transom. A trim cylinder  220  is also visible in  FIG. 11 . The primary intent of  FIG. 11  is to show the present invention in association with other components of an outboard motor to more clearly illustrate the relationship and location of the components of the present invention in conjunction with the outboard motor. The steering axis  45  of the outboard motor is illustrated in  FIG. 11  to show the axis about which the outboard motor rotates in response to forces provided by the couplers  100  on the first tie bar arm  51 . Two or more such outboard motors would be connected to the transom of a marine vessel and caused to rotate about their respective steering axis in tandem with each other. 
       FIG. 12  is a section view of the first tie bar arm  51  when used in conjunction with first and third connecting links,  61 ′ and  63 . The second clevis end  97  of the first connecting link  61 ′ is shaped to receive the extension portion  120  within it. Both the second clevis end  97  and the extension portion  120  are disposed between the first and second attachment plates,  91  and  92 , of the first tie bar arm  51 . A bolt  240  extends through the first tie bar arm  51  and through the first connecting link  61 ′ coaxially with the first axis  71 . The bolt  240  is a shoulder bolt which is sized to retain the first connecting link  61 ′ in an uncompressed state between the first and second attachment plates,  91  and  92 . At least one flanged radial bearing, illustrated as flanged radial bearing  251  and  252  in  FIG. 12 , is disposed around the bolt  240  and between the first and second attachment plates,  91  and  92 . A non-flanged radial bearing  260  is disposed around the bolt  240  and between the first and second attachment plates,  91  and  92 . 
     Also shown in  FIG. 12  is a retainer tab  270  that is located under the head of bolt  240  and on the top surface of the first attachment plate  91 . A protrusion  274  extends upwardly from the first attachment plate  91  and through an opening  276  formed in the retainer tab  270 . This prevents the retainer tab  270  from rotating about the first axis  71 . An edge  280  of the retainer tab  270  can be bent upwardly to lock the head of the bolt  240  and prevent it from rotating about the first axis  71 . 
     With continued reference to  FIG. 12 , it can be seen that the distal end  290  of the bolt  240  is threaded to be attached in threaded association with accommodating threads in the second attachment plate  92 . The bolt  240  is provided with a shoulder  292  which abuts a similarly shaped shoulder in the second attachment plate  92  above the threads that mesh with the threads of the bolt  240 . This defines the depth to which the bolt  240  can be moved downwardly relative to the first and second attachment plates,  91  and  92 . The use of the shoulder  292  prevents the first and second attachment plates,  91  and  92 , from being compressed towards each other by an overtightening of the bolt  240 . In other words, the location of the shoulder  292  assures that the first and second connecting links,  61 ′ and  63 , are not compressed between the first and second attachment plates,  91  and  92 , as a result of the bolts  240  being overtightened. The bearings,  251  and  252 , also assure that the first and second connecting links,  61 ′ and  63 , are free to rotate about the first axis  71 . 
     With reference to  FIGS. 4–12 , it has been shown that the connection system for connecting two marine propulsion devices together, according to a preferred embodiment of the present invention, comprises a first tie bar  51  which is attachable to a first one of the two marine propulsion devices and a first connecting link  61  which is pivotally connectable to the first tie bar arm  51  for rotation about a first axis  71 . The present invention further comprises a first rod assembly  81  which is pivotally connectable to the first connecting link  61  for rotation about a second axis  72 . A coupler  100  is attachable in a first direction of threaded association with the first rod assembly  81  and a second rod assembly  82  is attachable in a second direction of threaded association with a coupler  100 . The first and second directions of threaded association are opposite to each other, with one using a left hand thread and the other using a right hand thread. 
     A second connecting link  62  is pivotally connectable to the second rod assembly  82  for rotation about a third axis  72 . A second tie bar arm  52  is attachable to a second one of the two marine propulsion devices, or outboard motors. The second tie bar arm  52  is pivotally connectable to the second connecting link  62  for rotation about a fourth axis  74 . The first tie bar arm  51  comprises a first attachment plate  91  and a second attachment plate  92 . The first and second attachment plates,  91  and  92 , are generally parallel to each other. The first connecting link  61  is disposable between the first and second attachment plates. The first axis  71  extends through the first and second attachment plates,  91  and  92 , and also through the first connecting link  61 . The first connecting link  61  comprises a first clevis end  96 . The first rod assembly  81  is disposed within the first clevis end  96 . The second axis  72  extends through the first rod assembly  81  and through the first clevis end  96 . 
     In certain embodiments of the present invention, where three outboard motors are to be connected in tandem together, the first connecting link  61 ′ comprises a second clevis end  97  which is disposed between the first and second attachment plates,  91  and  92 . The first axis  71  extends through the first and second attachment plates and through the second clevis end  97 . The second clevis end is shaped to receive an extension portion  120  of a third connecting link  63 . 
     The first and second axes,  71  and  72 , extend in directions which are generally perpendicular to each other. The first and second axes are arranged in nonintersecting association with each other and separated by a distance which is determined by the size of the connecting link. The first direction of threaded association, which attaches the coupler  100  to the rod assemblies, employs a right handed thread and a left handed thread, one for each of the first and second rod assemblies. The first and second rod assemblies,  81  and  82 , are moved toward each other in response to rotation of the coupler  100  in a first direction R 1  about its central axis and are moved away from each other in response to rotation of the coupler  100  in an opposite direction R 2  about its central axis. This results from the use of two oppositely configured threads at the two ends of the coupler  100  and the corresponding use of two rod assemblies,  81  and  82 , that are provided with oppositely directed threads. 
     A bolt  240  extends through the first tie bar arm  51  and through the first connecting link,  61  or  61 ′. It should be understood that the first tie bar arm  51  and the first connecting link are configured in one manner when two outboard motors are connected together in tandem and the first connecting link  61 ′ is configured in another manner to suit the connection of three or more outboard motors together. The bolt  240  is a shoulder bolt which is sized to retain the first connecting link in an uncompressed state between the first and second attachment plates,  91  and  92 . At least one flanged radial bearing,  251  and  252 , is disposed around the bolt  240  and between the first and second attachment plates. A non-flanged radial bearing  260  is disposed around the bolt  240  between the first and second attachment plates. A first resultant force F exerted by the first connecting link  61  on the first tie bar arm  51  is symmetrical with a second resultant force R exerted by the first tie bar arm  51  on the first connecting link  61 . The first and second resultant forces are generally equal in magnitude and directed in opposite directions along a common axis. It should be understood that when a pair of connection plates,  91  and  92 , or the arms of a clevis end are used, either the first resultant force or the second resultant force will actually comprise two forces distributed between either the first and second attachment plates,  91  and  92 , or the two arms of a clevis end. As a result, the first and second resultant forces, F and R, combine to create approximately no net moment about any point. As a result of the structure of the present invention, the system is easily assembled and adjusted. The coupler  100  can be rotated about its centerline in either a first rotational direction R 1  or a second rotational direction R 2  to adjust the distance between the first and fourth axes. This can easily be done without having to detach the coupler  100  from its associated components or having to disconnect the connecting links,  61  and  62 , from their respective tie bar arms. In addition, the use of the clevis ends of the connecting links and the use of both first and second attachment plates of the first and second tie bar arms distributes the forces and their reactions in such a way that resulting moments are avoided. Therefore, bending forces on the various components are eliminated or significantly reduced. 
     Although the present invention has been described with particular specificity to show preferred embodiments and illustrated to show a particular structure, it should be understood that alternative embodiments are also within its scope.