Cantilever jet drive package having mounting adapter with exhaust passage

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.

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.degree. 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.

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.