Induction system for small watercraft

Abstract

An induction system for a 4-cycle engine of a small watercraft includes an improved construction that insulates the fuel injectors from engine-produced vibration and heat. The air induction system includes an air intake box defining the plenum chamber. The air intake box is supported from the engine by one or more stays. An insulating grommet is positioned between the air intake box and the stays. The air induction system also includes one or more throttle bodies within the plenum chamber which are connected to intake pipes external of the plenum chamber. The throttle bodies each support a fuel injector. Insulating sleeves are positioned between the throttle bodies and the intake pipes. Insulating rings are positioned between the throttle bodies and the air intake box.

Description

PRIORITY INFORMATION

[0001] This invention is based on and claims priority to Japanese Patent Applications No. 200-205618, filed Jul. 6, 2000, the entire contents of which are hereby expressly incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to an engine for a watercraft, and particularly to an improved air induction system of an engine for a watercraft.

[0004] 2. Description of the Related Art

[0005] Personal watercrafts have become very popular in recent years. This type of watercraft is quite sporting in nature and carries one or more riders. A relatively small hull of the personal watercraft commonly defines a rider's area above an engine compartment. An internal combustion engine powers a jet propulsion unit which propels the watercraft. The engine lies within the engine compartment in front of a tunnel formed on an underside of the hull. The jet propulsion unit, which includes an impeller, is placed within the tunnel. The impeller has an impeller shaft driven by the engine. The impeller shaft usually extends between the engine and the jet propulsion device through a bulkhead of the hull tunnel.

[0006] The engine includes an air induction system for delivering air into one or more combustion chambers. The engine also includes a fuel delivery system for introducing fuel into the one or more combustion chambers. In order to reduce emissions, the fuel delivery system often includes at least one electronically controlled fuel injector associated with the combustion chambers. An electronically controlled fuel injector is capable of more precise metering of fuel delivery than mechanical systems, such as carburetors.

[0007] Typically, the fuel injector is mounted to a component of the air induction system which, in turn, is mounted to the engine. Often, the fuel injector is mounted to a throttle body of the fuel delivery system. This arrangement results in vibration and heat produced by the engine to be transferred through the throttle body to the fuel injector. The electronic components of the fuel injector may be negatively affected by exposure to vibration and/or heat, which results in lower performance, decreased life and a higher rate of premature failure.

SUMMARY OF THE INVENTION

[0008] According to one aspect a preferred embodiment, a watercraft includes a hull defining an engine compartment. An internal combustion engine is positioned within the engine compartment. The engine includes an engine body which defines a combustion chamber. An air induction system is provided which is configured to guide air into the combustion chamber and includes an intake air chamber. An electronic component is supported within the intake chamber. A first insulating member connects the intake air chamber to the engine body.

[0009] According to another aspect of the preferred embodiment a marine duty engine includes an engine body which defines a combustion chamber. An air induction system is configured to guide air into the combustion chamber and includes an intake air chamber and a throttle body. An electrical component is disposed in the air chamber. A first insulating member connects air intake chamber to the engine.

[0010] According to another aspect the preferred embodiment, a watercraft includes a hull defining an engine compartment. An internal combustion engine is positioned within the engine compartment. The engine includes an engine body which defines a combustion chamber. An air induction system is provided which is configured to guide air into the combustion chamber and includes a throttle body. A fuel delivery system is provided which is configured to deliver fuel to the combustion chamber and includes a fuel injector. The fuel injector is supported by the throttle body. A first insulating member connects the throttle body to the engine.

[0011] In accordance with another aspect of the preferred embodiment, a small watercraft includes a hull defining an engine compartment. An internal combustion engine is positioned within the engine compartment. The engine includes an engine body which defines a combustion chamber. An air induction system is configured to guide air into the combustion chamber and includes a throttle body. A fuel delivery system is provided which is configured to deliver fuel to the combustion chamber and includes a fuel injector. The fuel injector is supported by the throttle body. Means for inhibiting engine produced vibrations from being transferred to the fuel injector is provided.

[0012] A still further aspect of a preferred embodiment involves a small watercraft including a hull defining an engine compartment. An internal combustion engine is positioned within the engine compartment. The engine includes an engine body which defines a combustion chamber. An air induction system is provided which is configured to guide air into the combustion chamber and includes a throttle body. A fuel delivery system is provided which is configured to deliver fuel to the combustion chamber and includes a fuel injector. The fuel injector is supported by the throttle body. Means for inhibiting engine produced vibrations from being transferred to the fuel injector is provided.

[0013] Further aspects, features and advantages of this invention will become apparent from the detailed description of the preferred embodiments which follow.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] These and other features, aspects and advantages of the present invention will now be described with reference to the drawings of preferred embodiments which are intended to illustrate and not to limit the invention. The drawings comprise 8 figures.

[0015] FIG. 1 is a side elevational view of a personal watercraft of the type powered by an engine configured in accordance with a preferred embodiment of the present invention. Several of the internal components of the watercraft (e.g., the engine) are illustrated in phantom.

[0016] FIG. 2 is a top plan view of the watercraft shown in FIG. 1.

[0017] FIG. 3 is a schematic and partial cross-sectional rear view of the watercraft and the engine. A profile of a hull of the watercraft is shown schematically. The engine including an air intake box and an opening of an engine compartment of the hull are illustrated partially in section.

[0018] FIG. 4 is a front, top, and right side perspective view of the engine shown in FIG. 3.

[0019] FIG. 5 is a front, top, and left side perspective view of the engine shown in FIG. 3.

[0020] FIG. 6 is a top plan view of the intake box. An upper chamber member is detached in this figure.

[0021] FIG. 7 is an enlarged cross-sectional view of a portion of the intake box shown in FIG. 3.

[0022] FIG. 8 is a cross-sectional view taken along the line 8-8 of FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0023] With reference to FIGS. 1 to 8, an overall configuration of a personal watercraft 10 is described below. An arrow F, present in several of the figures, indicates a forward direction of the watercraft 10.

[0024] The watercraft 10 employs an internal combustion engine 12 configured in accordance with a preferred embodiment of the present invention. The described engine configuration has particular utility with the personal watercraft, and thus, is described in the context of the personal watercraft 10. The engine configuration, however, can be applied to other types of watercrafts as well, such as, for example, small jet boats.

[0025] The personal watercraft 10 includes a hull 14 formed with a lower hull section 16 and an upper hull section or deck 18. Both the hull sections 16, 18 are made of, for example, a molded fiberglass reinforced resin or a sheet molding compound. The lower hull section 16 and the upper hull section 18 are coupled together to define an internal cavity 20 (FIG. 3). A gunnel 22 defines an intersection of both the hull sections 16, 18.

[0026] With reference to FIGS. 1 through 3, the hull 14 defines a center plane CP that extends generally vertically from bow to stern. Along the center plane CP, the upper hull section 18 includes a hatch cover 24, a control mast 26 and a seat 28 arranged from fore to aft.

[0027] In the illustrated embodiment, a bow portion 30 of the upper hull section 18 slopes upwardly and an opening (not shown) is provided through which the rider can access the internal cavity 20. The hatch cover 24 is detachably affixed (e.g., hinged) to the bow portion 30 so as to cover the opening.

[0028] The control mast 26 extends upwardly to support a handle bar 32. The handle bar 32 is provided primarily for controlling the direction in which the water jet propels the watercraft 10. Grips are formed at both ends of the bar 32 so that the rider can hold them for that purpose. The handle bar 32 also carries other control units such as, for example, a throttle lever 34 that is used for control of running conditions of the engine 12.

[0029] The seat 28 extends along the center plane CP to the rear of the bow portion 30. The seat 28 also generally defines a rider's area. The seat 28 has a saddle shape and hence a rider can sit on the seat 28 in a straddle-type fashion. Foot areas 36 are defined on both sides of the seat 28 on the top surface of the upper hull section 18. The foot areas 36 are formed generally flat.

[0030] A cushion supported by the upper hull section 18, at least in principal part, forms the seat 28. The seat 28 is detachably attached to the upper hull section 18. An access opening 38 is defined under the seat 28 through which the rider can also access the internal cavity 20. That is, the seat 28 usually closes the access opening 38. In the illustrated embodiment, the upper hull section 18 also defines a storage box 40 under the seat 28.

[0031] A fuel tank 42 is disposed in the cavity 20 under the bow portion 30 of the upper hull section 18. The fuel tank 42 is coupled with a fuel inlet port positioned at a top surface of the upper hull section 18 through a duct (not shown). A closure cap 44 closes the fuel inlet port. Optionally, the cap 44 can be positioned under the hatch cover 24.

[0032] The engine 12 is disposed in an engine compartment defined in the cavity 20. The engine compartment preferably is located under the seat 28, but other locations are also possible (e.g., beneath the control mast 26 or in the bow). The rider thus can access the engine 12 in the illustrated embodiment through the access opening 38 by detaching the seat 28.

[0033] A pair of air ducts or ventilation ducts 46 are provided on both sides of the bow portion 30 so that the ambient air can enter the internal cavity 20 therethrough. Optionally, the watercraft 10 can also include additional air ducts (not shown) which allow air to enter and exit the engine internal cavity 20 through a rear area thereof. Except for the air ducts, the engine compartment 20 is substantially sealed so as to protect the engine 12 and other components from water.

[0034] A jet pump unit 48 propels the watercraft 30. The jet pump unit 48 is mounted at least partially in a tunnel 50 formed on the underside of the lower hull section 36 which is preferably isolated from the engine compartment by a bulkhead (not shown). The tunnel 50 has a downward facing inlet port (not shown) opening toward the body of water. A jet pump housing 52 is disposed within a portion of the tunnel 50 and communicates with the inlet port. An impeller (not shown) is supported within the housing 52.

[0035] An impeller shaft 54 extends forwardly from the impeller and is coupled to a crankshaft 56 of the engine 12 by a coupling member 58. The crankshaft 56 of the engine 12 thus drives the impeller shaft 54.

[0036] The rear end of the housing 52 defines a discharge nozzle 59. A steering nozzle 60 is affixed to the discharge nozzle 59 for pivotal movement about a steering axis which extends generally vertically. The steering nozzle 60 is connected to the handle bar 32 by a cable so that the rider can pivot the nozzle 60.

[0037] As the engine 12 drives the impeller shaft 54 and hence rotates the impeller, water is drawn from the surrounding body of water through the inlet port (not shown). The pressure generated in the housing 52 by the impeller produces a jet of water that is discharged through the steering nozzle 60 which propels the watercraft 10. The rider can move the steering nozzle 60 with the handle bar 32 so as to turn the watercraft 30 in either direction.

[0038] The engine 12 operates on a four-stroke cycle combustion principle. With reference to FIG. 3, the engine 12 includes a cylinder block 62. The cylinder block 62 defines four cylinder bores 64 which are spaced from each other in a fore to aft direction along the center plane CP. The engine 12 thus is an L4 (in-line four cylinder) type. The illustrated engine, however, merely exemplifies one type of engine on which various aspects and features of the present invention can be used. Engines having other number of cylinders, having other cylinder arrangements, other cylinder orientations (e.g., upright cylinder banks, V-type, and W-type) and operating on other combustion principles (e.g., crankcase compression two-stroke, diesel, and rotary) are all practicable.

[0039] Each cylinder bore 64 has a center axis CA that is slanted or inclined at an angle from the center plane CP so that the engine 12 can be shorter in height. All the center axes CA in the illustrated embodiment are inclined at the same angle.

[0040] Pistons 66 reciprocate within the cylinder bores 64. A cylinder head member 68 is affixed to the upper end of the cylinder block 62 to close respective upper ends of the cylinder bores 64 and to define combustion chambers 70 with cylinder bores and the pistons 66.

[0041] A crankcase member 72 is affixed to the lower end of the cylinder block 62 to close the respective lower ends of the cylinder bores 64 and to define a crankcase chamber 74. The crankshaft 56 is rotatably connected to the pistons 66 through connecting rods 76 and is journaled with the crankcase member 72. That is, the connecting rods 76 are rotatably coupled with the pistons 66 and with the crankshaft 56.

[0042] The cylinder block 62, the cylinder head member 68, and the crankcase member 72 together define an engine body 78. The engine body 78 preferably is made of an aluminum based alloy.

[0043] In the illustrated embodiment, the engine body 78 is oriented in the engine compartment 20 so as to position the crankshaft 56 generally parallel to the central plane CP and to extend generally in the longitudinal direction. Other orientations of the engine body, of course, are also possible (e.g., with a transverse or vertical crankshaft).

[0044] Engine mounts 80 extend from both sides of the engine body 78. The engine mounts 80 preferably include resilient portions made of, for example, a rubber material. The engine 12 preferably is mounted on the lower hull section 16, specifically, a hull liner, by the engine mounts 80 so that vibrations from the engine 12 are attenuated.

[0045] The engine 12 preferably includes an air induction system to introduce air to the combustion chambers 70. In the illustrated embodiment, the air induction system includes at least four air intake ports 82 defined in the cylinder head member 68, i.e., one for each cylinder bore 64. The intake ports 82 communicate with the associated combustion chambers 70. Intake valves 84 are provided to selectively connect and disconnect the intake ports 82 with the combustion chambers 70. That is, the intake valves 84 selectively open and close the intake ports 82.

[0046] The air induction system also includes an air intake box 86, which defines a plenum chamber 88 within, for smoothing intake air and acting as an intake silencer. The intake box 86 in the illustrated embodiment, has a generally rectangular shape. Other shapes of the intake box of course are possible, but it is desired to make the plenum chamber as large as possible within the space provided in the engine compartment. In the illustrated embodiment, a space is defined between the top of the engine 12 and the bottom of the seat 28 due to the inclined orientation of the engine 12. The rectangular shape of the intake box 86 conforms to this space.

[0047] With reference to FIGS. 3 and 7, the intake box 86 comprises an upper chamber member 90 and a lower chamber member 92. The upper and lower chamber members 90, 92 preferably are made of plastic or synthetic resin, although they can be made of metal or other material. Additionally, the intake box 86 can be formed by a different number of members and/or can have a different assembly orientation (e.g., side-by-side).

[0048] With reference to FIG. 3, the lower chamber member 92 preferably is coupled with the engine body 78. In the illustrated embodiment, several stays 94 extend upwardly from the engine body 78 and a flange portion 96 of the lower chamber member 92 extends generally horizontally.

[0049] Several fastening members, for example, bolts 98, connect the flange portion 96 to respective top surfaces of the stays 94. The upper chamber member 90 has a flange portion 100 (FIG. 1) that abuts on the flange portion 96 of the lower member 92. Several coupling or fastening members 102, which are generally configured as a shape of the letter “C” in section, preferably engage both the flange portions 96, 84 so as to couple the upper chamber member 90 with the lower chamber member 92. The intake box 86 thus is disposed in a space defined between the engine body 78 and the seat 28, i.e., the rider's area of the hull 34, so that the air intake box 86 defines a relatively large volume plenum chamber 88 therein.

[0050] With reference to FIG. 3, 6 and 8, the lower chamber member 92 defines an inlet opening 104 and, preferably, four outlet apertures 106. Four throttle bodies 108 extend through the apertures 106 and preferably are fixed to the lower chamber member 92. Respective bottom ends of the throttle bodies 108 are coupled with the associated intake ports 82. Preferably, as illustrated in FIG. 3, the position at which the apertures 106 are sealed to the throttle bodies 108 is spaced from the outlet of “bottom” ends of the throttle bodies 108. Thus, the lower member 92 is spaced from the engine 12, thereby attenuating transfer of heat from the engine body 78 into the intake box 86.

[0051] With reference to FIG. 3, the throttle bodies 108 slant toward the port side away from the center axis CA of the cylinder bores 64. A sleeve 110, described in greater detail below, extends between the lower chamber member 92 and the cylinder head member 68 so as to generally surround a portion of the throttle bodies 108. Respective top ends of the throttle bodies 108, in turn, open upwardly within the plenum chamber 88. Air in the plenum chamber 88 thus is drawn to the combustion chambers 70 through the throttle bodies 108 and the intake ports 82 when negative pressure is generated in the combustion chambers 70. The negative pressure is generated when the pistons 66 move toward the bottom dead center from the top dead center.

[0052] With reference to FIGS. 6 and 8, each throttle body 108 includes a throttle valve 112. A throttle valve shaft 114, journaled for pivotal movement, links the throttle valves 112. Pivotal movement of the throttle valve shaft 114 is controlled by the throttle lever 58 on the handle bar 56 through a control cable that is connected to the throttle valve shaft 114. The rider thus can control opening amount of the throttle valves 112 by operating the throttle lever 56 so as to obtain various running conditions of the engine 12 that the rider desires. That is, an amount of air passing through the throttle bodies 108 is controlled by this mechanism and delivered to the respective combustion chambers 70.

[0053] With reference to FIG. 3, air is introduced into the plenum chamber 88 through the air inlet port 104. In the illustrated embodiment, a filter assembly 116 surrounds the inlet port 104. The filter assembly 116 comprises an upper plate 118, a lower plate 120 and a filter element 122 interposed between the upper and lower plates 118, 120. Preferably, the filter element 122 comprises oil resistant and water-repellant elements.

[0054] The lower plate 120 includes a duct 124 which extends inwardly toward the plenum chamber 88. The duct 124 is positioned generally above the cylinder head member 68. An upper end of the duct 124 slants so as to face an inner wall portion of the intake box 86 positioned opposite the throttle bodies 108. In the illustrated embodiment, the upper or outlet ends of the ducts 124 define a high point proximate to the outlet apertures 106 and a low point distal from the apertures 106. This is advantageous because water or water mist, if any, is likely to move toward this inner wall portion rather than toward the throttle bodies 108. If, however, a smooth flow of air is desired more than the water inhibition, the upper end of the duct 124 can slant toward the throttle bodies 108 as indicated by the phantom line 124a of FIG. 3. Optionally, the upper ends of some of the ducts 124 can slant away from the throttle bodies 108 and the rest can slant toward the throttle bodies 108.

[0055] In the illustrated embodiment, a guide member 126 is affixed to the lower plate 120 immediately below the duct 124. The guide member 126 defines a recess 128 that is associated with duct 124. The recess 128 opens toward the starboard side. The air in the cavity 20 of the engine compartment thus is drawn into the plenum chamber 88 along the recess 128 of the guide member 126 and then through the duct 124.

[0056] The filter assembly 116, including the lower plate 120, has a generally rectangular shape in plan view. The filter element 122 extends along a periphery of the rectangular shape so as to define a gap between a peripheral edge of the filter element 122 and an inner wall of the air box 86. The duct 124 opens to an interior volume 130 defined by the filter element 122. The air in this volume 130 thus cannot reach the throttle bodies 108 without passing through the filter element 122. Foreign substances in the air are removed by the filter element 122 accordingly.

[0057] Because the air inlet openings 104 are formed at the bottom of the intake box 86, water and/or other foreign substances are unlikely to enter the plenum chamber 88. Additionally, the filter element 106 further prevents water and foreign particles from entering the throttle bodies 108. In addition, part of the openings 104 are defined as the ducts 106 extending into the plenum chamber 88. Thus, a desirable length for efficient silencing of intake noise can be accommodated within the plenum chamber 90.

[0058] The engine 12 also includes a fuel supply system as illustrated in FIGS. 1, 3, 6 and 8. The fuel supply system includes the fuel tank 42 (FIG. 1) and fuel injectors 132 that are affixed to a fuel rail 134 and are mounted on the throttle bodies 108. The fuel rail 134 extends generally horizontally in the longitudinal direction. A fuel inlet port 136 is defined at a forward portion of the lower chamber member 92 so that the fuel rail 134 is coupled with an external fuel passage. Because the throttle bodies 108 are disposed within the plenum chamber 88, the fuel injectors 132 are also desirably positioned within the plenum chamber 88. However, other types of fuel injectors can be used which are not mounted in the intake box 86, such as, for example, but without limitation, direct fuel injectors and induction passage fuel injectors connected to the scavenge passages of two-cycle engines. Each fuel injector 132 has an injection nozzle directed toward the intake port 82 associated with each fuel injector 132.

[0059] Sprayed fuel is delivered to the combustion chambers 70 with the air when the intake ports 82 are opened to the combustion chambers 70 by the intake valves 84. The air and the fuel are mixed together to form air/fuel charges which are then combusted in the combustion chambers 70.

[0060] With reference to FIGS. 3-5, the engine 12 further includes an exhaust system 138 to discharge burnt charges, i.e., exhaust gases, from the combustion chambers 70. In the illustrated embodiment, with reference to FIG. 3, the exhaust system 138 includes a plurality of exhaust ports 140, at least one for each combustion chamber 70. The exhaust ports 140 are defined in the cylinder head member 68 and communicate with the associated combustion chambers 70. Exhaust valves 142 are provided to selectively connect and disconnect the exhaust ports 140 with the combustion chambers 70. That is, the exhaust valves 142 selectively open and close the exhaust ports 140.

[0061] The exhaust system includes an exhaust manifold 144. In a presently preferred embodiment, the manifold 144 comprises a first manifold 146 and a second manifold 148 (FIG. 4) coupled with the exhaust ports 140 to receive exhaust gases from the respective ports 140. The first manifold 146 is connected to two of the exhaust ports 140 and the second manifold 148 is connected with the other two exhaust ports 140. In a presently preferred embodiment, the first and second manifolds 146, 148 are configured to nest with each other.

[0062] Respective downstream ends of the first and second exhaust manifolds 146, 148 are coupled with a first unitary exhaust conduit 150. As seen, for example, in FIGS. 5 and 6, the first unitary conduit 150 is further coupled with a second unitary exhaust conduit 152. The second unitary conduit 152 is then coupled with an exhaust pipe 154 on the rear side of the engine body 78.

[0063] With reference to FIG. 5, the exhaust pipe 154 extends along a side surface of the engine body 78 on the port side. The exhaust pipe 154 is then connected to a water-lock 156 at a forward surface of the water-lock 156. With reference to FIG. 2, a discharge pipe 158 extends from a top surface of the water-lock 156 and transversely across the center plane CP. The discharge pipe 158 then extends rearwardly and opens at a stem of the lower hull section 36 in a submerged position. The water-lock 156 inhibits the water in the discharge pipe 158 from entering the exhaust pipe 154.

[0064] With reference to FIG. 4, the engine 12 preferably includes a secondary air supply system 160 that supplies air from the air induction system to the exhaust system 138. More specifically, for example, hydro carbon (HC) and carbon monoxide (CO) components of the exhaust gases can be removed by an oxidation reaction with oxygen (O2) that is supplied to the exhaust system 138 from the air induction system.

[0065] With reference to FIG. 3, the engine 12 has a valve cam mechanism for actuating the intake and exhaust valves 84, 142. In the illustrated embodiment, a double overhead camshaft drive is employed. That is, an intake camshaft 162 actuates the intake valves 84 and an exhaust camshaft 164 separately actuates the exhaust valves 142. The intake camshaft 162 extends generally horizontally over the intake valves 84 from fore to aft generally parallel to the center plane CP, and the exhaust camshaft 164 extends generally horizontally over the exhaust valves 142 from fore to aft also generally parallel to the center plane CP.

[0066] Both the intake and exhaust camshafts 162, 164 are journaled by the cylinder head member 68 with a plurality of camshaft caps. The camshaft caps holding the camshafts 162, 164 are affixed to the cylinder head member 68. A cylinder head cover member 166 extends over the camshafts 162, 164 and the camshaft caps, and is affixed to the cylinder head member 68 to define a camshaft chamber. The stays 94 and the secondary air supply device 142 are preferably affixed to the cylinder head cover member 166. Additionally, the air supply device 142 is desirably disposed between the intake air box 86 and the engine body 78.

[0067] The intake camshaft 162 has cam lobes each associated with a respective intake valves 84, and the exhaust camshaft 164 also has cam lobes associated with respective exhaust valves 142. The intake and exhaust valves 84, 142 normally close the intake and exhaust ports 82, 140 by a biasing force of springs. When the intake and exhaust camshafts 162, 164 rotate, the cam lobes push the respective valves 84, 142 to open the respective ports 82, 142 by overcoming the biasing force of the spring. The air thus can enter the combustion chambers 70 when the intake valves 84 open. In the same manner, the exhaust gases can move out from the combustion chambers 70 when the exhaust valves 142 open.

[0068] The crankshaft 56 preferably drives the intake and exhaust camshafts 162, 164. The respective camshafts 162, 164 have driven sprockets affixed to ends thereof. The crankshaft 56 also has a drive sprocket. Each driven sprocket has a diameter which is twice as large as a diameter of the drive sprocket. Preferably, a timing chain or belt is wound around the drive and driven sprockets. When the crankshaft 56 rotates, the drive sprocket drives the driven sprockets via the timing chain, and thus the intake and exhaust camshafts 162, 164 also rotate. The rotational speed of the camshafts 150, 238 are reduced to half as the rotational speed of the crankshaft 56 because of the differences in diameters of the drive and driven sprockets.

[0069] Ambient air enters the internal cavity 20 defined in the hull 34 through the air ducts 46. The air is then introduced into the plenum chamber 88 defined by the intake box 86 through the air inlet ports 98 and drawn into the throttle bodies 108. The majority of the air in the plenum chamber 88 is supplied to the combustion chambers 70. The throttle valves 112 in the throttle bodies 108 regulate an amount of the air passing to the combustion chambers 70. The opening angles of the throttle valves 112 are controlled by the rider with the throttle lever 58 and thus controls the airflow across the valves. The air hence flows into the combustion chambers 70 when the intake valves 84 open. At the same time, the fuel injectors 132 spray fuel into the intake ports 82 under the control of ECU. Air/fuel charges are thus formed and delivered to the combustion chambers 70.

[0070] The air/fuel charges are fired by the spark plugs 216 under the control of the ECU. The burnt charges, i.e., exhaust gases, are discharged to the body of water surrounding the watercraft 30 through the exhaust system 138. A relatively small amount of the air in the plenum chamber 88 is supplied to the exhaust system 138 through the secondary air supply system 160 so as to aid in further combustion of any unburnt fuel remaining in the exhaust gases.

[0071] The combustion of the air/fuel charges causes the pistons 66 reciprocate and thus causes the crankshaft 56 to rotate. The crankshaft 56 drives the impeller shaft 54 and the impeller rotates in the hull tunnel 50. Water is thus drawn into the tunnel 50 through the inlet port 76 and then is discharged rearward through the steering nozzle 60. The rider steers the nozzle 60 by the steering handle bar 56. The watercraft 30 thus moves as the rider desires.

[0072] Primarily with reference to FIGS. 6 through 8, the air induction system 138, and specifically the throttle body 108 mounting arrangement is described in greater detail below.

[0073] With reference to FIG. 6, the lower chamber member 92 of the air intake box 86 is illustrated with the upper chamber member 90 removed. The lower chamber member 92 includes a pair of brackets 168, each including a through hole 170, for connecting the air intake box 86 to the stays 94 (FIG. 3).

[0074] With reference to FIG. 7, a mounting arrangement of a single junction between the stay 94 and the air intake box 86 is illustrated. Preferably, each mounting junction between each stay 94 and the air intake box 86 is constructed in accordance with the arrangement illustrated in FIG. 7. As described in relation to FIG. 3, the air intake box 86 is supported by one or more stays 94 extending between the engine 12 and the air intake box 86. A bolt 98 and nut 99 secure the air intake box 86 to the stay 94.

[0075] An insulating grommet 172 is positioned concentrically within the through hole 170 of the air intake box 86. The grommet 172 preferably includes a substantially cylindrical shaped central portion 174 and a flange portion 176 of larger diameter on each end. Preferably, the central portion 174 nests within the through hole 170 with one of the flange portions 176 engaging the upper surface of the bracket 168 and one of the flange portions engaging the lower surface of the bracket 168. Preferably, the grommet 172 is constructed from a material which inhibits the transfer of vibration and heat, such as an elastomeric or rubber material, for example.

[0076] The grommet 172 additionally includes a central aperture 178 passing axially therethrough. A collar 180 having a flange portion 182 at one end is positioned within the central aperture 178 of the grommet 172. A washer 184 is positioned at the opposite end from the flange portion 182 of the collar 180. The flange portion 182 of the collar 180 preferably is supported by a transversely extending tab 186 of the stay 94. The bolt 98 is passed through the washer 184, collar 180 and stay 94 and is secured in place by the nut 99. Thus, the grommet 172 is positioned intermediate the air intake box 86 and the stay 94 to inhibit engine vibration and/or heat, which is transferred to the stay 94, from being passed to the air intake box 86.

[0077] With reference to FIG. 8, a mounting arrangement of the throttle body 108 is illustrated. FIG. 8 is a cross section of a throttle body 108 taken along line 8-8 of FIG. 6. Although only one throttle body 108 is illustrated in FIG. 8, preferably the remaining throttle bodies 108 are of a similar or identical construction.

[0078] An intake pipe 188 defines an intake runner 190 of the engine 12. The intake runner 190 communicates with the intake port 82 (FIG. 3). The throttle body 108 is connected to the intake pipe 188 by the sleeve 110, described in greater detail below. The throttle body 108 defines an aperture for supporting the fuel injector 132 in a position to communicate with the intake runner 190.

[0079] The insulating sleeve 110 is secured to the intake pipe 188 by a hose clamp 194. The end of the sleeve 110 opposite the intake pipe 188 defines an annular recess 196 for receiving a collar 198. The collar 198 may be held by the resilient nature of the sleeve 110 material. However, the collar 198 may also be secured to the sleeve 110 by an adhesive. Alternatively, the sleeve 110 may be injection molded around the collar 198 during manufacturing. Other suitable connection methods may also be used.

[0080] The sleeve 110 and collar 198 assembly extends through the opening 106 of the air intake box 86. A flange portion 200 of the collar 198 cooperates with a flange portion 202 of the throttle body 108 to secure a portion of the air intake box 86 therebetween. A bolt 204 secures the throttle body 108 to the sleeve 110 and collar 198 assembly and, thus, to the intake pipe 188. Desirably, a washer 206 is positioned between the bolt 204 and throttle body 108. Advantageously, the insulating sleeve 110 inhibits vibration and/or heat from being transferred from the engine 12 to the throttle body 108.

[0081] An insulating ring 208 is positioned between both the throttle body 108, collar 198, and the air intake box 86. The insulating ring 208 operates to inhibit engine vibration and/or heat from being transferred to the throttle body 108 through the air intake box 86.

[0082] The above-described induction system arrangement inhibits vibration and/or heat produced by the engine 12 from being transferred to the throttle bodies 108, either directly through the engine 12 or indirectly through the stays 94 and air intake box 86. Such a construction is particularly advantageous due to the fuel injectors 132 being connected to the throttle bodies 108. The fuel injectors 132 contain electronic components that may be sensitive to vibration and heat. Insulating engine-produced vibration and heat from reaching the fuel injectors 132 increases their performance and operating life while reducing the likelihood of premature failure.

[0083] Of course, the foregoing description is that of a preferred embodiment of the present invention, and various changes and modifications may be made without departing from the spirit and scope of the invention, as defined by the appended claims.

Claims

1. A watercraft comprising a hull defining an engine compartment, an internal combustion engine disposed in the engine compartment, the engine including an engine body defining a combustion chamber, an air induction system comprising an intake air chamber configured to guide air toward the combustion chamber, an electrical component disposed within the air chamber, and an insulating member supporting the air chamber relative to the engine body.

2. The watercraft according to claim 1, wherein the electrical component is a fuel injector.

3. The watercraft according to claim 1 additionally comprising a throttle body connected to the air chamber, the engine body including at least one intake port, the insulating member comprising an elastic member connecting the throttle body to the intake port.

4. The watercraft of claim 3, additionally comprising an intake runner extending from the intake port toward the throttle body, the elastic member connecting the intake runner to the throttle body.

5. The watercraft of claim 1 additionally comprising a throttle body having an outlet end, a collar connected to the outlet end of the throttle body, wherein the insulating member comprises an inlet end configured to engage the collar.

6. The watercraft according to claim 5, when the throttle body is connected to the air chamber, the insulating member comprising an elastic member having an inlet end configured to engage the collar sufficiently to support at least part of the air chamber.

7. The watercraft according to claim 5, wherein the inlet end of the insulating member comprises an annularly shaped channel configured to extend along an inner surface of the collar and an outer surface of the collar.

8. The watercraft according to claim 1 additionally comprising at least one stay extending from a portion of the engine body other than the intake port to the air chamber.

9. The watercraft according to claim 8 wherein the portion of the engine body comprises a cam chamber cover.

10. The watercraft according to claim 1, wherein the insulating member is elastic.

11. A marine-duty engine including an engine body defining a combustion chamber, an air induction system configured to guide air into the combustion chamber, the air induction system comprising an intake air chamber configured to guide intake air toward the combustion chamber, an electrical component disposed within the air chamber, and an insulating member connecting the air chamber with the engine body.

12. The engine according to claim 11, wherein the electrical component is a fuel injector.

13. The engine according to claim 11 additionally comprising a throttle body connected to the air chamber, the engine body including at least one intake port, the insulating member comprising an elastic member connecting the throttle body to the intake port.

14. The engine of claim 13, additionally comprising an intake runner extending from the intake port toward the throttle body, the elastic member connecting the intake runner to the throttle body.

15. The engine of claim 11 additionally comprising a throttle body having an outlet end, a collar connected to the outlet end of the throttle body, wherein the insulating member comprises an inlet end configured to engage the collar.

16. The engine according to claim 15, when the throttle body is connected to the air chamber, the insulating member comprising an elastic member having an inlet end configured to engage the collar sufficiently to support at least part of the air chamber.

17. The engine according to claim 15, wherein the inlet end of the insulating member comprises an annularly shaped channel configured to extend along an inner surface of the collar and an outer surface of the collar.

18. The engine according to claim 11 additionally comprising at least one stay extending from a portion of the engine body other than the intake port to the air chamber.

19. The engine according to claim 18 wherein the portion of the engine body comprises a cam chamber cover.

20. The engine according to claim 11, wherein the insulating member is elastic.

21. A watercraft comprising a hull defining an engine compartment, an internal combustion engine disposed in the engine compartment, the engine including an engine body defining a combustion chamber, an air induction system configured to guide air into the combustion chamber, the air induction system comprising an intake air chamber configured to guide intake air toward the combustion chamber, an electrical component disposed in the air chamber, and means for insulating the electrical component from engine produced vibrations.

22. The watercraft according to claim 21, wherein the electrical component is a fuel injector.

23. The watercraft according to claim 21 additionally comprising a throttle body connected to the air chamber, the electrical component being connected to the throttle body.

24. A small watercraft comprising a hull defining an engine compartment, an internal combustion engine disposed in the engine compartment, the engine including an engine body defining a combustion chamber, an air induction system configured to guide air into the combustion chamber, the air induction system comprising and intake air chamber configured to guide intake air toward the combustion chamber, an electrical component disposed in the air chamber, and means for insulating the electrical component from engine produced heat.

25. The watercraft according to claim 24, wherein the electrical component is a fuel injector.

26. The watercraft according to claim 24 additionally comprising a throttle body connected to the air chamber, the electrical component being connected to the throttle body.