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.

Abstract: A driveshaft supporting structure for a watercraft is provided that supports in a substantially watertight manner at least a portion of a driveshaft. The 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.

Abstract: An impeller for a jet propulsion device includes at least one fluid channel formed on each impeller blade. During impeller rotation, a fluid back-flow is generated through the fluid channels. The back-flow advantageously sweeps cavitation bubbles away from the impeller blades and inhibit their implosion on the blade surfaces and/or inner housing surface which lies adjacent the blade tips. This desirably reduces erosion and provides a long-life and efficient propulsion device.

Abstract: An impeller for a jet propulsion device includes at least one fluid channel formed on each impeller blade. During impeller rotation, a fluid back-flow is generated through the fluid channels. The back-flow advantageously sweeps cavitation bubbles away from the impeller blades and inhibit their implosion on the blade surfaces and/or inner housing surface which lies adjacent the blade tips. This desirably reduces erosion and provides a long-life and efficient propulsion device.

Abstract: An induction system employed in an engine of a small watercraft includes the first intake chamber communicating with the combustion chambers within the engine and a second intake chamber communicating with the first intake chamber. At least one auxiliary air aperture is provided in the first intake chamber so as to allow an auxiliary flow of air into the first intake chamber during, for example, sudden acceleration.

Abstract: An induction system employed in an engine of a small watercraft includes the first intake chamber communicating with the combustion chambers within the engine and a second intake chamber communicating with the first intake chamber. At least one auxiliary air aperture is provided in the first intake chamber so as to allow an auxiliary flow of air into the first intake chamber during, for example, sudden acceleration.

Abstract: A number of embodiments of induction systems for watercraft that employ, in addition to the plenum chamber of the air inlet device for the induction system, a further plenum chamber of a predetermined volume that communicates with the induction system plenum chamber for providing silencing and/or tuning effects to improve induction efficiency and silencing. In addition there are disclosed compact intake devices that incorporate plenum chambers for this purpose.

Abstract: An air inlet device for an engine powering a water propulsion device of a watercraft, the watercraft having a hull defining an engine compartment in which the engine is positioned, is disclosed. The engine has a body defining at least one combustion chamber and an output shaft arranged to drive the water propulsion device. Air is supplied to the combustion chamber of the engine through the air inlet device. This device includes an intake pipe extending outwardly from the engine and an air box connected to the intake pipe. The air box has a cover having a top and a bottom and defining an interior air chamber, an air inlet provided near the top of the air box and a drain provided through the bottom of the air box. The intake pipe has a passage therethrough leading from the interior air chamber of the air box to said engine. The air box has a width at the top which is greater than a width at the bottom.

Abstract: A water inlet tap for an engine cooling system is provided on a jet propulsion unit of a small watercraft. The inlet tap includes a filter element arranged at the inlet of the tap so as to lie generally flush with in inner surface of the jet propulsion unit. In this position, the principal flow of water through the jet propulsion unit tends to sweep away debris at the inlet of the tap in order inhibit fouling of the filter. The filter, as well as the tap itself, are removably attached to one side of the jet propulsion unit for easy servicing.

Abstract: A fuel increasing mechanism for supplying fuel to an engine positioned in an engine compartment defined by a hull of a watercraft is disclosed. The engine is arranged to power a water propulsion device associated with the watercraft and has a body defining at least one combustion chamber. The engine includes an intake system for routing air to the combustion chamber, the intake system extending from the body of the engine. The fuel increasing mechanism includes an accelerating pump for supplying fuel to air passing through the intake system, the accelerating pump positioned on a side of the intake system generally opposite the body of the engine.

Abstract: A fuel increasing mechanism for supplying fuel to an engine positioned in an engine compartment defined by a hull of a watercraft is disclosed. The engine is arranged to power a water propulsion device associated with the watercraft and has a body defining at least one cylinder. The engine includes an intake system for routing air to the cylinder, the intake system extending from the body of the engine at an angle offset from a centerline through the cylinder, whereby a space is defined above the engine between the body and intake system. The fuel increasing mechanism includes an accelerating pump for supplying fuel to air passing through the intake system, the accelerating pump positioned on a side of the intake system so as to be located in the space defined between the intake system and engine body.

Abstract: A steering arrangement for a watercraft that includes a jet propulsion unit having a jet propulsion unit housing. The housing includes an inlet end and a discharge end with a propeller provided therebetween for drawing water from the inlet end and discharging the water in the form of a pressurized jet stream to the discharge end. The discharge end includes a fixed nozzle through which the jet stream of pressurized water flows. A pivoting nozzle is pivotally coupled to the discharge nozzle for guiding the jet stream of pressurized water for steering operation of the watercraft. A seal is effected between the discharge nozzle and steering nozzle upon steering action of the pivoting nozzle so as to prevent a generally forward flowpath of water between the fixed nozzle and pivoting nozzle.

Abstract: A seal arrangement for a marine propulsion drive that insures good sealing and adequate lubrication.

Abstract: A water-removal assembly for removing accumulated water from the bilge of a hull of a watercraft that includes a jet propulsion unit with an impeller. The water-removal assembly includes a water pickup provided in the engine compartment. A means for removing water from the engine compartment and preventing water from entering and syphoning into the engine compartment is connected to the water filter by a first conduit. The conduit connects the water removing and preventing means to a water discharge point in the jet propulsion unit so that water is pumped from the bilge. The water removing and preventing means includes a check valve that allows water to flow in one direction so that water is prevented from entering the bilge. A weep hole is provided in the water removing and preventing means to prevent syphoning from occurring in the water-removal assembly.

Abstract: A water jet propulsion assembly for a jet ski-type watercraft includes an annular duct including a first section within which an impeller is located, a second section having a group of sloping vane members extending radially therethrough and a third section formed with a group of straight vane member extending partially radially inwardly from the inside surface of the outermost duct wall. The duct terminates in a nozzle for expelling water flowing therethrough. The second section of the duct includes radially inner and outer wall portions and the inner portion has a cap member secured to a rear end thereof. The cap member extends into the third duct section and is formed with another group of straight vane member which extend radially outwardly. The vane members function to convert the swirling water flow created by the impeller into a linear flow that is directed through the nozzle. The sloping and straight vane members are divided to permit more efficient molding of the vane sections by die casting.

Abstract: A water jet propelled boat is equipped with a water intake opening, a water jet outlet, and with a mixed flow type impeller, where the above mentioned water intake opening and the above mentioned water jet outlet are connected by a water passage with the impeller in the middle of the water passage, and where the operation of the impeller causes water to be drawn into the water intake opening and expelled through the above mentioned water outlet to propel the boat. The impeller structure is such that a boss section of the impeller has a plurality fins affixed to it, the outside edges of the above mentioned spiral fins are roughly parallel to the axial center of the above mentioned boss, and, the leading and the trailing edges of the fins, with respect to the axial center of the above described boss, slant down toward the above mentioned water outlet opening. At the same time relative speeds, the invention allows a smaller diameter fin unit and, at speeds of 4,000 rpm and over, it offers improved efficiency.