Abstract:
A marine vessel or watercraft in which the power plant or engine is cantilevered off of the inboard face of the transom by a mounting adapter. An inboard engine is attached to the mounting adapter. By this arrangement, the mounting adapter provides cantilevered support to the engine. The engine has at least one exhaust port for engine exhaust gases. The mounting adapter has an exhaust channel in flow communication with an exhaust port of the inboard engine. In addition, the transom has an opening in flow communication with the exhaust channel of the mounting adapter. Thus the passage in the mounting adapter provides a flow path for engine exhaust gases to pass through an opening in the hull. Optionally the exhaust channel in the mounting adapter includes a noise suppression device, e.g., a muffler.

Description:
RELATED PATENT APPLICATION 
     This application is a continuation-in-part application claiming priority from U.S. patent application Ser. No. 09/265,075 filed on Mar. 9, 1999, now U.S. Pat. No. 6,132,269. 
    
    
     FIELD OF THE INVENTION 
     This invention generally relates to inboard motors for powering water jet propulsion units in boats and other watercraft. In particular, the invention relates to inboard engines cantilevered to transoms of watercraft. 
     BACKGROUND OF THE INVENTION 
     It is known to propel a boat or other watercraft using a water jet apparatus mounted to the hull, with the powerhead placed inside (inboard) the hull and an axialflow water jet apparatus mounted outside the boat below the waterline. The drive shaft of the water jet apparatus is coupled to the crankshaft of the motor. The water jet apparatus comprises an impeller mounted on the drive shaft and a housing surrounding the impeller. The interior surface of the housing defines a water tunnel. The impeller is designed such that during motor operation, the rotating impeller impels water rearward through the water tunnel and out an exit nozzle. The reaction force of the rearward water flow exiting the jet propulsion device propels the watercraft forward. 
     To facilitate use of jet-propelled boats in shallow water, it is known to mount the water jet propulsion unit at an elevation such that the propulsion unit does not project below the bottom of the boat hull. This can be accomplished, for example, by installing a duct in the stern of the boat, the duct being arranged to connect one or more inlet holes formed in the bottom of the hull with an outlet hole formed in the transom. The pump jet is then installed outside the hull in a position such that the pump jet inlet is in flow communication with the duct outlet at the transom. 
     Typically the jet drive power plant is mounted on stringers built into the hull of a boat for in-line drive applications or on an adapter plate mounted to stringers for 90° drive applications. It is also known to mount a marine engine to the inboard or forward face of a transom in a cantilever arrangement. In such a cantilevered arrangement, it is conventional practice to provide a hole in the transom through which the engine drive shaft passes. 
     There is a need for a design whereby a water jet propulsion unit is powered by an engine cantilevered from the transom. The mounting arrangement should also incorporate means for venting exhaust gases from the engine to a locus below the waterline and behind the transom. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a marine vessel or watercraft in which the power plant or engine is cantilevered off of the inboard face of the transom by a mounting adapter. In accordance with the preferred embodiment of the invention, the mounting adapter is attached to the transom on the inboard side thereof, and an inboard engine is attached to the mounting adapter. By this arrangement, the mounting adapter provides cantilevered support to the engine. 
     In accordance with the preferred embodiment, the engine comprises at least one exhaust port for engine exhaust gases. The mounting adapter comprises an exhaust channel in flow communication with an exhaust port of the inboard engine. In addition, the transom comprises an opening in flow communication with the exhaust channel of the mounting adapter. Thus the passage provides a flow path for engine exhaust gases to pass through an opening in the hull. Optionally the exhaust channel in the mounting adapter comprises a noise suppression device, e.g., a muffler. 
     Furthermore, a transom mounting plate is attached to the transom on its aft side. This transom mounting plate provides cantilevered support for a jet propulsion unit and comprises an exhaust pipe in flow communication with the opening in the transom. The exhaust pipe has an outlet which is located below the hull waterline. In accordance with the preferred embodiment, the transom mounting plate further comprises a tube portion having an inlet in flow communication with a water tunnel formed in the hull and an outlet in flow communication with an inlet of the jet propulsion unit. Preferably the exhaust pipe or manifold branches into two exhaust pipes which straddle the tube portion. 
     Preferably, each of the transom mounting plate and the mounting adapter is a cast metal structure. Also the transom mounting plate and the mounting adapter are preferably attached to the transom (on opposite sides thereof) by the same set of fasteners, with the transom sandwiched therebetween. The shafts of the fasteners are preferably encased in rubber isolation mounts to prevent the transmission of vibrations from the engine to the transom and the transom mounting plate. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic showing an elevational partly sectional view of the stern of a jet-powered watercraft in accordance with the preferred embodiment of the invention. 
     FIG. 2 is a schematic showing a rear elevational view of a transom mounting plate incorporated in the watercraft depicted in FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1, there is shown in cross section a molded hull  10  of a marine vessel having a bottom hull portion  12  extending from a transom portion  14  to a forward bow of the boat (not shown). As shown, the hull bottom  12  is attached to the transom  14  in a fluid-tight manner. The hull bottom  12  has a water inlet (not shown) which communicates with a channel or tunnel  16  formed as part of the molded hull. The bottom of a portion of the tunnel can be closed by a bolted-on inlet structure having a built-in grate (not shown). The other end of the tunnel  16  communicates with an inlet opening of a conventional water jet propulsion unit  18 , mounted aft of the transom by means of a transom mounting plate  2  attached to an aft face  20  of the transom  14 . 
     The transom mounting plate  2  (shown in FIG. 2) is preferably a sand-cast metal structure comprising a plate, a tube portion  8  connected at one end to a lower portion of the plate, and an exhaust manifold  4  which branches into separate pipes that straddle the tube portion  8 . The ends of the exhaust pipes are open to form respective exhaust outlets  6 . The aft end of the tube portion  8  is provided with conventional means (e.g., a flange with threaded holes) for attaching a water jet propulsion unit. 
     Referring again to FIG. 1, the tube portion  8  effectively becomes an extension of the water duct or tunnel  16 , i.e., is in flow communication with the water duct  16 . Preferably the shape of the tube portion  8 , at the inlet where it meets the water duct  16 , should conform to the shape of the latter, thereby allowing water to flow along a smooth transition from the water duct  16  into the tube portion  8 . Similarly, the inlet to the water jet propulsion unit  18  is in flow communication with the outlet of tube portion  8 . Thus tube portion  8  of the transom mounting plate  2  guides flowing water from the water duct  16  into the jet propulsion unit. 
     One conventional type of water jet propulsion unit comprises an impeller (not shown) mounted to a drive shaft  48  and a housing  50  surrounding the impeller. The impeller draws in ambient water via the duct  16  and the water inlet (not shown) of that duct, formed in the hull bottom  12 . The water inlet is preferably covered by a grating or screen (not shown) to prevent debris from entering the duct  16 , thereby avoiding damage to the impeller inside the water jet propulsion unit  18 . The impeller housing  50  is in flow communication with a thrust nozzle  52  having a decreasing cross-sectional area to increase the velocity of the impelled water passing therethrough. A steering nozzle  54  is pivotally mounted to the thrust nozzle by means of a pair of pivot pin assemblies  56 . The water flow exiting the steering nozzle  54  can be reversed by activation of a conventional reverse gate  42 , which causes exiting water to flow through a slot  44  formed in the steering nozzle  54  and in a reverse direction. The steering and shifting controls for controlling the positions of the steering nozzle and the reverse gate comprise well-known structures such as cables, links and levers. These structures are not shown in the drawings to avoid unnecessary complication in the depiction of the preferred embodiment. 
     As shown in FIG. 1, the water jet propulsion unit is powered by a powerhead or engine  24 . The engine  24  may be any suitable power source, such as a gasoline or diesel internal combustion engine. The engine could be a 2-cycle or a 4-cycle engine which has the necessary power for driving the boat. As shown, at the forward end of engine  24 , there is included a drive plate assembly  35  which is coupled to a crankshaft  58  of engine  24 . Drive plate assembly  35  extends below the bottom of the engine  24  as shown and provides a drive output  40  at a point below the engine, namely the forward end of the drive shaft  48 , the rear end of which is coupled to the impeller. It will be appreciated that the crankshaft  58  of the engine  24  may be coupled to the drive output  40  by any suitable transmission technique, including a fixed ratio belt drive, such as indicated by pulleys  60  and  64  which are connected by belt  62 . It will also be appreciated by those skilled in the art that a fixed ratio gear drive could readily be substituted for the fixed ratio belt drive. Further, it is also possible to use a changeable ratio gear drive or a continuous variable transmission for transferring the power from the crankshaft  58  of the engine  24  to the drive output  40 . There may also be included in any of the above-mentioned drive mechanisms an electric clutch such that the engine and transmission include a neutral setting. 
     In accordance with a further feature of the preferred embodiment, the drive shaft  48  is rotatably supported by a bearing  68  incorporated in the drive plate assembly and is isolated from the vibrations produced by the operating engine by means of an isolation coupler  66  which damps and vibrations. In addition, a watertight seal assembly  70  allows leakage-free passage of the drive shaft  48  through the hull of the boat. As a result, when the engine  24  is operating and power is being transmitted to drive shaft  48  from drive output  40  through isolation coupler  66 , water will be drawn into the duct or passage  16  and then impelled out the steering nozzle  54  by the impeller of the jet propulsion unit  18 . 
     In accordance with the preferred embodiment of the invention, the engine  24  is cantileverly mounted to the transom  14  by means of a mounting adapter  26 , which is attached to the inboard face  22  of the transom by means of a multiplicity of fastener assemblies  30  (e.g., a nut and bolt assembly) which penetrate the transom  14  at different elevations. The mounting adapter  26  is preferably a sandcast metal structure designed to support the engine in cantilever fashion. Preferably the mounting adapter has a pair of transom mounting flanges  28  (only one of which is visible in FIG. 1) on opposing sides of the adapter. Each transom mounting flange  28  has a plurality of holes which align with corresponding holes  10  (seen in FIG. 2) formed in the transom mounting plate  2 , as well as with corresponding holes formed in the transom  14 . Thus, it should be apparent that each fastener  30  passes through a transom mounting flange  28  of the mounting adapter  26 , the transom  14 , and the transom mounting plate  2 . These fastener assemblies fasten the mounting adapter  26  to the inboard face  22  of the transom and fasten the transom mounting plate  2  to the aft face  20  of the transom, sandwiching the transom therebetween. 
     Preferably the mounting adapter is designed to have a shape to assure that the engine  24  is maintained in a horizontal position. The mounting adapter  26  is cast with a pair of engine mounting flanges  32  (only one of which is visible in the figure). Similarly, the engine  24  is provided with a pair of mounting flanges  34  (again, only one is visible). The aft end of the engine is mounted to the forward face of the mounting adapter by fastening the flanges  34  of the engine to the respective engine mounting flanges  32  using fasteners (not shown). 
     In addition, the mounting adapter  26  is designed with a plurality of external reinforcement ribs  36 , which extend from bosses formed on the transom mounting flanges  28 . These bosses surround and reinforce the holes in the transom mounting flanges which are penetrated by the fasteners  30 . To help prevent vibrations of the engine being transmitted to the boat, rubber mounts  31  are installed in the penetration holes in the transom  14 , which rubber mounts are in turn surround the shaft of the bolts passing therethrough. Thus it can be seen that the engine or power source  24  is cantileverly mounted to the transom  14 . 
     In addition to providing cantilevered support for the engine, the mounting adapter is also designed to serve as an exhaust manifold. In accordance with the preferred embodiment of the invention, an exhaust port of the engine is in flow communication with an opening  72  in the transom via a flow passage or channel  10  formed when the mounting adapter is cast. If the engine has more than one exhaust port, then an equal number of branches can be provided. In the latter case, the branches meet to form a single main channel in flow communication with the transom opening  72 . In accordance with a further preferred embodiment, a muffler  11  can be built into the mounting adapter to suppress engine noise. Although not shown in FIG. 1, the person skilled in the art will readily appreciate that the inlet of the muffler  11  must be in flow communication with the engine exhaust port (or ports) via a first passage (or respective passages) formed in the mounting adapter, while the outlet of the muffler will be in flow communication with the transom opening  72  via a second passage 
     In accordance with the preferred embodiment of the invention, the transom mounting plate  2  is also designed to play a role in the exhaustion of exhaust gases from the engine. More particularly, the transom mounting plate  2  comprises an exhaust manifold  4  having an inlet in flow communication with the transom opening  72 . As best seen in FIG. 2, the exhaust manifold  4  starts as a single pipe and then branches into a pair of exhaust pipes which straddle the tube portion (and the portion of the jet propulsion unit connected thereto). As best seen in FIG. 1, each exhaust pipe of exhaust manifold  4  has an exhaust outlet  8  which is located at an elevation below the centerline of the jet propulsion unit, i.e., the exhaust outlets  6  will be disposed below the waterline when the vessel is waterborne. 
     Thus, the preferred embodiments of the invention provide an engine exhaust system for a cantilever-mounted inboard engine which is easy to build and requires a minimum of connections. 
     While the invention has been described with reference to preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation to the teachings of the invention without departing from the essential scope thereof. Therefore it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.