Abstract: The invention relates to an interface for mounting a propulsion mechanism to a watercraft such as a fishing kayak, and to a watercraft comprising such an interface. The interface comprises a first portion including a first plate with a hole sized and shaped for receiving therethrough a portion of the propulsion mechanism, a second portion including a second plate and one channel extending from the second plate, the channel being in registry with the hole of the first portion for therein a portion of the propulsion mechanism. The interface also comprises fastening assemblies for removably fastening the second portion to the first portion of the interface, and a guiding assembly for maintaining the channel of the second portion in registry with the hole of the first portion.

Abstract: The invention relates to an interface for mounting a propulsion mechanism to a watercraft such as a fishing kayak, and to a watercraft comprising such an interface. The interface comprises a first portion including a first plate with a hole sized and shaped for receiving therethrough a portion of the propulsion mechanism, a second portion including a second plate and one channel extending from the second plate, the channel being in registry with the hole of the first portion for therein a portion of the propulsion mechanism. The interface also comprises fastening assemblies for removably fastening the second portion to the first portion of the interface, and a guiding assembly for maintaining the channel of the second portion in registry with the hole of the first portion.

Abstract: An outboard motor and methods of use thereof in general, includes a powerhead removeably affixed to the transom of a boat, and a gear case rotationally connected to a propeller shaft, the outboard motor including a telescopic drive shaft, the telescopic drive shaft having a first drive shaft section rotationally connected to the motor and a second drive shaft section rotationally connected to the gear case, and a telescopic drive shaft housing, the telescopic drive shaft housing configured to support the telescopic drive shaft internally therethrough, whereby the telescopic drive shaft and the telescopic drive shaft housing are configured to provide depth adjustment for the gear case and the propeller shaft, and thus enable the propeller to be raised and lowered during propulsion to improve propulsion efficiency.

Abstract: An apparatus is for supporting an outboard motor on a transom of a marine vessel. The apparatus has a transom bracket configured for fixed attachment to the transom; a supporting cradle that supports the outboard motor with respect to the transom bracket, wherein the supporting cradle is pivotable with respect to the transom bracket about a trim axis; and a trim actuator that is pivotally coupled to the transom bracket at a first trim actuator pivot axis and to the supporting cradle at a second trim actuator pivot axis. Extension of the trim actuator pivots the supporting cradle upwardly about the trim axis. Retraction of the trim actuator pivots the supporting cradle downwardly about the trim axis. The trim axis is located aftwardly of the first trim actuator pivot axis.

Abstract: The invention relates to an interface for mounting a propulsion mechanism to a watercraft such as a fishing kayak, and to a watercraft comprising such an interface. The interface comprises a first portion including a first plate with a hole sized and shaped for receiving therethrough a portion of the propulsion mechanism, a second portion including a second plate and one channel extending from the second plate, the channel being in registry with the hole of the first portion for therein a portion of the propulsion mechanism. The interface also comprises fastening assemblies for removably fastening the second portion to the first portion of the interface, and a guiding assembly for maintaining the channel of the second portion in registry with the hole of the first portion.

Abstract: A reverse gear includes an input shaft, a forward clutch, a reverse clutch, an output shaft, a reduction mechanism, and a relay shaft. The input shaft receives rotational power of a main engine. The forward clutch transmits the rotational power of the input shaft as forward output. The reverse clutch transmits the rotational power of the input shaft as reverse output. The output shaft outputs the rotational power transmitted via the forward clutch and the reverse clutch. The reduction mechanism reduces the rotational power of the output shaft and transmits the reduced rotational power to the propeller shaft. The relay shaft intersects the input shaft and relays the rotational power from the forward clutch and the reverse clutch toward the output shaft. The relay shaft and the output shaft are coupled to each other via a pair of intersecting-shaft gears to be able to transmit power.

Abstract: Disclosed herein is an inventive dual propeller assembly that can be manually or automatively assembled and includes a leading propeller, and a trailing propeller which are coaxially aligned and secured with a propeller shaft and a locking nut. Various embodiments are disclosed with and without interior grooves for alignment. In all embodiments, the two propellers are secured and aligned with a propeller shaft and locking nut assembly.

Abstract: An outboard motor includes an upper case, a lower case including an oil reservoir chamber, an oil flow passage, and an oil flow passage shutoff valve. When the lower case is detached from the upper case, the oil flow passage is separated into an upper oil flow passage in the upper case and a lower oil flow passage in the lower case and connected to the oil reservoir chamber. The oil flow passage shutoff valve opens the lower oil flow passage in a state in which the lower case has been attached to the upper case. The oil flow passage shutoff valve closes the lower oil flow passage in a state in which the lower case has been detached from the upper case.

Abstract: An outboard motor includes an outboard motor main body including an engine and a propeller driven by the engine, an upper bracket to attach the outboard motor main body to a hull, and a pair of antivibration mounts. The pair of antivibration mounts are joined to the upper bracket, and sandwich and elastically support a portion of the outboard motor main body from the left and the right of the outboard motor main body. The pair of antivibration mounts are arranged side by side in the left-right direction so that a center of rolling of the outboard motor main body is located between the pair of antivibration mounts in the left-right direction, and are bilaterally asymmetrical to each other.

Abstract: Upper anti-vibration mounts have axial lines arranged in parallel to a longitudinal center line extending in a longitudinal direction of the outboard motor body. Lower anti-vibration mounts have axial lines concentrated on one point on the longitudinal center line extending in a longitudinal direction of the outboard motor body. Meanwhile, the axial lines are inclined at the identical angle symmetrically with respect to the longitudinal center line, so that they intersect in a V-shape in front of the support shaft as seen in a plan view of the outboard motor body.

Abstract: A system for mounting an outboard motor propulsion unit to a marine vessel transom is disclosed. The propulsion unit's midsection has an upper end supporting an engine system and a lower end carrying a gear housing. The mounting system includes a support cradle having a head section coupled to a transom bracket, an upper structural support section extending aftward from the head section and along opposite port and starboard sides of the midsection, and a lower structural support section suspended from the upper structural support section and situated on the port and starboard sides of the midsection. A pair of upper mounts couples the upper structural support section to the midsection proximate the engine system. A pair of lower mounts couples the lower structural support section to the midsection proximate the gear housing. At least one of the upper and lower structural support sections comprises an extrusion or a casting.

Abstract: In an upper mount portion, a steering central axis related to a steering force of a steering handle and a vibration central axis related to a torque reaction force of an engine are configured to be shifted back and forth. A mount member is formed such that a spring constant related to the vibration central axis is smaller than a spring constant related to the steering central axis.

Abstract: An outboard-motor vibration-isolating cooler system apparatus providing a retrofit substitute for the midsection and the lower unit of a standard outboard motor, having a substitute closed-loop cooling system with an exterior heat exchanger, a substitute oil reservoir, a substitute exhaust system, and a substitute propulsion system with an isolating power-take-off shaft, allowing an existing standard outboard-motor powerhead to be used in conditions not conducive to standard open-loop water cooling, such as shallow-water, muddy-water, obstructed-water, seawater, or corrosive-water conditions.

Abstract: An outboard-motor vibration-isolating cooler system method providing a retrofit substitute for the midsection and the lower unit of a standard outboard motor, having a substitute closed-loop cooling system with an exterior heat exchanger, a substitute oil reservoir, a substitute exhaust system, and a substitute propulsion system with an isolating power-take-off shaft, allowing an existing standard outboard-motor powerhead to be used in conditions not conducive to standard open-loop water cooling, such as shallow-water, muddy-water, obstructed-water, seawater, or corrosive-water conditions.

Abstract: A tiller is for an outboard motor. The tiller comprises a supporting chassis having a first end and an opposite, second end. A rotatable throttle grip is supported on the first end and a pivot joint is located at the second end. The pivot joint is configured to facilitate pivoting of the tiller at least into and between a horizontal position wherein the supporting chassis extends horizontally and a vertical position wherein the supporting chassis extends vertically. A top cover is located on the supporting chassis. The top cover and the supporting chassis together define an interior of the tiller. The top cover is located vertically on top of the supporting chassis when the tiller is in the horizontal position.

Abstract: An outboard motor has a drive unit including an engine rotating output shaft and a driveshaft extending along a driveshaft axis and having an upper end coupled in torque-transmitting relationship with the output shaft. A propulsor shaft extends along a propulsor shaft axis and has a first end coupled in torque-transmitting relationship to a lower end of the driveshaft and a second end coupled to a propulsor. The propulsor shaft axis defines a direction of thrust generated by the propulsor. A transom bracket couples the drive unit to the marine vessel. A steering support couples the drive unit to the transom bracket and rotates the drive unit about a steering axis to change a direction of the thrust generated by the propulsor. The steering axis is substantially non-parallel to the driveshaft axis, and is oriented with respect to the driveshaft axis at a given angle of less than 45 degrees.

Abstract: An outboard motor includes an internal combustion engine, and an adapter plate having an upper end that supports the engine and a lower end formed as a cylindrical neck. A driveshaft housing below the adapter plate has an integral oil sump collecting oil that drains from the engine and through the adapter plate neck. One or more bearings couple the adapter plate neck to the oil sump such that the driveshaft housing is suspended from and rotatable with respect to the adapter plate. A driveshaft is coupled to a crankshaft of the engine, and extends along a driveshaft axis through the adapter plate neck, bearing(s), and oil sump. A steering actuator is coupled to and rotates the oil sump, and thus the driveshaft housing, around the driveshaft axis with respect to the adapter plate, which varies a direction of the outboard motor's thrust.

Abstract: A vessel propulsion apparatus includes an engine main body including a crankshaft that is rotatable about a rotation axis extending in the up-down direction, auxiliary machinery mounted on the engine main body, a bracket that couples the auxiliary machinery to the engine main body, and an engine cowling that houses the engine main body, the auxiliary machinery, and the bracket. The bracket includes a first mounting portion mounted on the engine main body, a second mounting portion mounted on the auxiliary machinery, a coupling portion coupling the first mounting portion and the second mounting portion, and a holding portion provided in the coupling portion. The holding portion of the bracket holds piping.

Abstract: A mounting arrangement is for supporting an outboard motor with respect to a marine vessel extending in a fore-aft plane. The mounting arrangement comprises first and second mounts that each have an outer shell, an inner wedge concentrically disposed in the outer shell, and an elastomeric spacer between the outer shell and the inner wedge. Each of the first and second mounts extend along a axial direction, along a vertical direction that is perpendicular to the axial direction, and along a horizontal direction that is perpendicular to the axial direction and perpendicular to the vertical direction. The inner wedges of the first and second mounts both have a non-circular shape when viewed in a cross-section taken perpendicular to the axial direction. The non-circular shape comprises a first outer surface that extends transversely at an angle to the horizontal and vertical directions.

Abstract: In one embodiment, the outboard motor lock comprises an outboard motor lock bracket and an outboard motor lock securing mechanism. The bracket comprises a back plate, side plates and a lip, and may be attached to a boat hull or other surface through bracket attachment holes. The securing mechanism comprises a base and one or more securing rods. The securing mechanism can be inserted into the bracket by inserting the one or more securing rods through corresponding bracket securing holes. One or more aligned bracket locking holes and securing mechanism locking holes allow for a locking device to be passed through and lock the securing mechanism to the bracket. When the securing mechanism is inserted into the bracket after an outboard motor attaching mechanism has engaged the bracket, the securing mechanism prevents the attaching mechanism from being removed from the bracket.

Abstract: A hull seal assembly securing a drive unit within an opening in a boat hull may include a lower housing section, an upper housing section and an intermediate housing section of the drive unit, with the intermediate housing section having an outwardly extending retention portion. The hull seal assembly further includes a hull support ring mounted to a bottom of the boat hull and surrounding the opening and a clamp ring installed around the drive unit. with the hull support ring having a downwardly facing support ring surface; and fastened to the hull support ring and having an upwardly facing clamp ring surface. The outwardly extending retention portion may be disposed between a downwardly facing support ring surface and an upwardly facing clamp ring surface to retain the outwardly extending retention portion of the drive unit within the hull support ring.

Abstract: A cooling device of an outboard engine unit includes a cooling water passage for delivering cooling water from a water pump. The cooling water passage branches into a first passageway for cooling a cylinder block and cylinder head of an engine and a second passageway for cooling a case of a supercharger. Thus, the supercharger and the engine can be cooled to and kept at their respective appropriate temperatures.

Abstract: In an outboard motor, a first damper member is disposed between a bracket and a casing such that the first damper member supports a weight of an outboard motor body. A second damper member is disposed between the bracket and the casing. The casing or the bracket includes a left first inclined surface and a right first inclined surface. The left first inclined surface and the right first inclined surface are inclined with respect to a front-back direction of the outboard motor body in a planar view of the outboard motor body. The second damper member includes a left second inclined surface and a right second inclined surface. The left second inclined surface is arranged to oppose the left first inclined surface. The right second inclined surface is arranged to oppose the right first inclined surface.

Abstract: A drive unit mount has a tapering central rigid member, top and bottom rigid members, and top and bottom resilient members. The top and bottom surfaces of the central rigid member, the bottom surface of the top rigid member and the top surface of the bottom rigid member have winding lateral cross-sections. A space defined between the bottom surface of the top rigid member and a top surface of the bottom rigid member tapers at least in part from the fronts of the top and bottom rigid members to the backs of the top and bottom rigid members. The top and bottom resilient members are disposed between and are in contact with the central rigid member and a corresponding one of the top and bottom rigid members. A drive unit mount having a rear resilient member and a marine outboard engine having a drive unit mount are also disclosed.

Abstract: An outboard motor includes an engine, a flywheel, a twisting member, and a damper. The engine includes a crankshaft that is rotatable around a crank axis extending in the up-down direction and includes an upper end portion disposed along the crank axis. The flywheel includes a joint portion that is disposed above the upper end portion of the crankshaft and joined to the upper end portion. The twisting member is disposed along the crank axis above the upper end portion of the crankshaft, and is arranged to rotate around the crank axis together with the crankshaft. The damper is disposed above the flywheel at a distance from the flywheel, and joined to the twisting member.

Abstract: An outboard motor includes an engine, a flywheel, a twisting member, and a damper. The engine includes a crankshaft that is rotatable around a crank axis extending in the up-down direction and includes an upper end portion disposed along the crank axis. The flywheel includes a joint portion that is disposed above the upper end portion of the crankshaft and joined to the upper end portion. The twisting member is disposed along the crank axis above the upper end portion of the crankshaft, and is arranged to rotate around the crank axis together with the crankshaft. The damper is disposed above the flywheel at a distance from the flywheel, and joined to the twisting member.

Abstract: An outboard engine unit having a cover halved into two. An undercover is made of a resin and halved into a left resin half and a right resin half. A lower mount cover is made of a resin and halved into a left resin half and a right resin half. The resin halves are formed so that when they are mated together, a gap is defined at a connection therebetween on a rear face side of the outboard engine unit. An elastic rubber member is filled in the gap.

Abstract: A joint 10 is shown for transmission of torque between an input shaft 12 and an output shaft 14. In the form shown, the joint 10 comprises an outermost helical coil spring 16 and an innermost helical coil spring 18, both of which are connected at their respective opposite ends to the input shaft 12 and to the output shaft 14. The innermost helical spring 18 is arranged to be entirely located within, and co-axially aligned with, the outermost helical spring 16 along the same centerline. The springs 16, 18 are arranged to be counter wound relative to one another to provide delivery of torque in a stabilised manner reflected in a significant reduction in the vibration observed within the joint 10 during use. The joint 10 is also arranged for transmission of thrust (or axial force) between the input shaft 12 and the output shaft 14.

Abstract: An outboard motor that is capable of reducing a trolling noise includes an engine which has a crank shaft extending in an up-down direction; a drive shaft extending downward from the crank shaft and including a torsion bar spring; a propeller shaft; a propeller provided in the propeller shaft; a forward/backward switching mechanism arranged to connect the drive shaft and the propeller shaft with each other; and a vibration damper which includes a first cylindrical body and a second cylindrical body which are penetrated by the torsion bar spring. The first cylindrical body and the second cylindrical body are coaxial with each other. The first cylindrical body has its upper end portion connected with an upper end portion of the torsion bar spring whereas the second cylindrical body has its lower end portion connected with a lower end portion of the torsion bar spring. A viscous fluid is filled between the first cylindrical body and the second cylindrical body.

Abstract: A mount structure of an outboard motor includes a first member, a second member, a buffer member, a sandwiching member, and a second elastic member. A propulsive force generated by a propeller of the outboard motor is applied to the first member. The second member is arranged such that the propulsive force is transmitted to the second member via the first member. The buffer member includes an outer sleeve fixed to the first member, an inner sleeve inserted in the outer sleeve, a first elastic member fixed to the outer sleeve and the inner sleeve. The sandwiching member is arranged to sandwich the second member and the inner sleeve in a direction of action of the propulsive force. The second elastic member is fixed to the first member. The second elastic member is opposed to the sandwiching member across a gap in the direction of action.

Abstract: A support system for an outboard motor uses mounts which are configured and positioned to result in an elastic center point being located closely to a roll axis of the outboard motor which is generally vertical and extends through a center of gravity of the outboard motor. The mounts are positioned so that lines which are perpendicular to their respective center lines intersect at an angle which can be generally equal to 90 degrees. The mounts are positioned in non-interfering relationship with the exhaust components of the outboard motor and its oil sump.

Abstract: A mount for supporting part of a marine drive system to a marine hull, the mount comprising a rigid outer housing (832) defining a radially outer circumferential surface on its radially inner surface, a resilient mounting (831) disposed radially within the outer housing and defining a radially inner circumferential surface, the marine drive system passing through and supported by the resilient mounting in use, wherein a circumferential radial gap is provided either between the resilient mounting and the rigid outer housing or within the resilient mounting.

Abstract: A marine outboard engine has a cowling, an engine, a driveshaft operatively connected to the crankshaft, a gear case, a transmission disposed in the gear case and connected to the driveshaft, a propeller shaft disposed generally perpendicular to the driveshaft and operatively connected to the transmission, and a bladed rotor connected to the propeller shaft. A pair of engine mounts are operatively connected to the engine. Each engine mount defines an engine mount working axis. A steering shaft is operatively pivotally connected to the engine mounts. The engine mount working axes are generally perpendicular to the steering axis and pass through the steering shaft. A stern bracket is operatively pivotally connected to the steering shaft for mounting the outboard engine to a boat. A marine outboard engine where primary axes of the engine mounts pass through the steering shaft is also disclosed.

Abstract: A mounting arrangement is provided for mounting a boat drive to a boat hull and includes a mounting collar including a first plate having a first opening therein and a first wall extending from a top surface of the first plate around the first opening and defining a first cylinder. The mounting arrangement also includes a clamping collar including a second plate having a second opening therein and a second wall extending from a top surface of the second plate around the second opening and defining a second cylinder, an external shape of at least a top end of the first cylinder substantially matching an internal shape of at least a bottom end of the second cylinder.

Abstract: An outboard motor that is capable of reducing a trolling noise includes an engine which has a crank shaft extending in an up-down direction; a drive shaft extending downward from the crank shaft and including a torsion bar spring; a propeller shaft; a propeller provided in the propeller shaft; a forward/backward switching mechanism arranged to connect the drive shaft and the propeller shaft with each other; and a vibration damper which includes a first cylindrical body and a second cylindrical body which are penetrated by the torsion bar spring. The first cylindrical body and the second cylindrical body are coaxial with each other. The first cylindrical body has its upper end portion connected with an upper end portion of the torsion bar spring whereas the second cylindrical body has its lower end portion connected with a lower end portion of the torsion bar spring. A viscous fluid is filled between the first cylindrical body and the second cylindrical body.

Abstract: A propeller thrust transmission device includes a taper portion of a propeller shaft that is fitted in a spacer divided into a first half and a second half. A thrust force acting on a propeller is received by the taper portion of the propeller shaft through the spacer. The first half includes a taper hole having an inner surface which corresponds in shape to an outer surface of the taper portion and in which the taper portion is fitted. The second half has a smaller diameter portion extending from one side of a ring-shaped wall portion closer to the propeller and fitted in a hole of an attachment device spaced from the propeller shaft, and a larger diameter portion extending from the other side of the ring-shaped wall portion and fitted on an outer peripheral surface of the first half.

Abstract: The invention is an accessory vibration damper that is applied over the diameter of any submersible electric motor housing of any modern electric trolling motor. Vibration damper is molded as a single unitary piece of an elastomeric compound that can have plural appendages placed perpependicular to the rotating armature of motor. Said appendages counteract the frequency range of vibrations produced while electric trolling motor is under propulsion.

Abstract: A marine drive system mounted in the hull of a marine craft, the marine drive system comprising an engine connected to a gearbox by means of a drive shaft (532), a propeller (1) connected to the gearbox by means of a propeller shaft (501), wherein the gearbox and the propeller are formed as a single rigid body for flexibly mounting in the hull of the marine craft as a single unit, and wherein the engine, gearbox and propeller are positioned such that they are always generally aligned with the longitudinal axis of the craft.

Abstract: To provide a small watercraft capable of suppressing vibration and noise of a vessel body, a jet pump is mounted to a hull via a thrust plate. A dynamic damper is disposed as an adjunct at a plate mounting portion that attaches the thrust plate to the hull. More specifically, the thrust plate is first mounted to the hull. Then, with a flange portion of the jet pump pressed up against a rear surface of the thrust plate, a second bolt is screwed in toward the thrust plate from an outward side of the hull. The jet pump is thereby attached to the rear surface of the thrust plate.

Abstract: A covering created to be attached to an electric trolling motor propulsion unit and/or shaft in order to absorb the sounds and vibrations created during the use of the trolling motor. The Invention is created from a material, such as rubber or synthetic rubber or of another material with sound dampening qualities, which dampens and/or absorbs sound, force and/or vibrations. The preferred embodiment of the Invention is a customized rubber or synthetic rubber covering that is applied flush to a portion of a trolling motor propulsion unit and/or shaft thereby reducing the vibrations distributed into the water into which the trolling motor is submerged and thus minimizing aquatic disturbance. Additional purposes of this method and apparatus is to both protect the trolling motor from damage caused by external trauma or blows and to dampen sounds and vibrations created from such external trauma.

Abstract: A marine propulsion support system incorporates a vibration isolation structure which comprises a plurality of elastomeric support components, or mounts. The vibration isolation structure is disposed between a marine vessel and a propulsion drive mounting transom to which a marine propulsion component, such as an outboard motor, can be attached. Support of the propulsion drive mounting transom by the marine vessel extends through the vibration isolation structure so that elastomeric portions of the elastomeric support components can damp any vibration emanating from a marine propulsion device, such as an outboard motor, and a deck of a pontoon boat or other marine vessel.

Abstract: A propeller for a boat includes a propeller shaft having a shaft hole, a shaft sleeve mounted in the shaft hole of the propeller shaft and provided with a metal core with a through hole for insertion of a driving shaft of the boat, and a shock-absorbing member covering an outer surface of the metal and having an outer surface contacted with an inner surface of the propeller shaft that surrounds the shaft hole; and a lock unit mounted on the driving shaft for fixing the driving shaft in the through hole of the shaft sleeve, so that the propeller is rotatable by the driving shaft. When the propeller bumps hard things during rotation to result in vibration to the propeller, the shock-absorbing member can absorb the vibration so as to protect the driving shaft from damage.

Abstract: A power damping mechanism for an input shaft of an auxiliary machine of an engine that is configured to be driven by the engine via a power transmission mechanism is provided. The power damping mechanism comprises a retainer plate that is fastened to the input shaft of the auxiliary machine and is rotatable with the input shaft, the retainer plate having a plurality of tubular retainer portions arranged to be equally spaced apart from each other in a circumferential direction; a damping member having a damping portion that is fitted to each of the retainer portions and is made of an elastic material, and a fastening portion by which the damping portion is fastened to the power transmission mechanism. The input shaft of the auxiliary machine is coupled to the power transmission mechanism via the damping member and is configured to operate in association with the power transmission mechanism.

Abstract: A joint 10 is shown for transmission of torque between an input shaft 12 and an output shaft 14. In the form shown, the joint 10 comprises an outermost helical coil spring 16 and an innermost helical coil spring 18, both of which are connected at their respective opposite ends to the input shaft 12 and to the output shaft 14. The innermost helical spring 18 is arranged to be entirely located within, and co-axially aligned with, the outermost helical spring 16 along the same centerline. The springs 16, 18 are arranged to be counter wound relative to one another to provide delivery of torque in a stabilised manner reflected in a significant reduction in the vibration observed within the joint 10 during use. The joint 10 is also arranged for transmission of thrust (or axial force) between the input shaft 12 and the output shaft 14.

Abstract: An outboard motor has a construction in which the area of an exhaust passage can be secured easily and exhaust noise is less likely to escape into the air, allowing the exhaust noise to be lowered. The outboard motor includes a lower case, a propeller shaft rotatably supported in the lower case, a propeller fixed to the propeller shaft, an engine, and a power transmission mechanism through which a driving force from the engine is transmitted to the propeller shaft to rotate the propeller. An exhaust case is provided in the lower case. The exhaust case includes an upper exhaust passage above the propeller shaft, the upper exhaust passage directing therethrough an exhaust gas from the engine, an exhaust outlet which is open in a rearward direction of the propeller shaft, and a communication exhaust passage arranged to communicate the upper exhaust passage with the exhaust outlet.

Abstract: In an outboard motor, an extension case (member constituting a frame of the outboard motor) has the natural frequency (resonance frequency) of higher than the vibration frequency produced when the engine operates at maximum speed. Since this configuration prevents the extension case from resonating during operation of the outboard motor, noise (more specifically, noise produced by the outboard motor) propagated to the outside can be reduced.

Abstract: An outboard motor adapted to be mounted on a stern of a boat includes an internal combustion engine installed on a frame and a propeller powered by the engine to propel the boat, elastic members (rubber vibration isolators, elastic couplings, etc.) are interposed between the engine and the frame, thereby enabling vibration and noise produced by engine operation to be reduced without degrading steering performance.

Abstract: An internal combustion engine is provided for a personal watercraft in which a portion of the engine that is enlarged to accommodate a balance shaft is minimized in size, whereby the internal combustion engine is made compact. Balance shafts for preventing secondary vibration are arranged together with a crankshaft on a dividing plane between a crankcase and a cylinder block of an internal combustion engine. The balance shafts lie mutually in parallel with the crankshaft. A crankshaft bearing is formed in the dividing plane on each of plural mutually opposed, longitudinally spaced rib pairs, and balance shaft bearing is formed in the dividing plane on a selected rib pair of the plural rib pairs. The balance shaft bearing is positioned so as to be biased in a direction in which the balance shaft bearing is closer to an adjacent rib compared with the crankshaft bearing.

Abstract: The support structure for an outboard motor provides a connection bar between an engine support structure and a steering structure. A tubular outer member is spaced apart from the attachment bar and connected to the attachment bar with an elastomeric member. Vibration isolation and consistency of deformation is achieved through the interaction of the individual elements of the structure.

Abstract: A drive shaft supporting structure for a watercraft is provided that supports in a substantially watertight manner at least a portion of the driveshaft. The drive shaft extends from an engine, which is disposed within an inner section of a hull of the watercraft (e.g., an engine compartment), to a propulsion unit that is disposed outside the inner section of the hull. The driveshaft supporting structure includes a bearing part that is mounted on a peripheral surface of the driveshaft at a location within the inner section of the hull. An elastic part is mounted on a peripheral surface of the bearing part and a bearing part supporting section supports a press-fitted assembly of the elastic part and the bearing part. The bearing part supporting section is attached to a wall of the hull (e.g., a duct wall) at a location where the driveshaft extends from the inner section of the hull.