Abstract: A jet propulsion system for a submersible vehicle, such as a submarine includes a propulsion unit mounted away from the stern of the submersible. Generally, the propulsion system consists of a set of blades secured to a hub within a shroud. Combining such a propulsion system with a surface texture treatment greatly reduces overall drag while improving the submersible's efficiency. Further, such an arrangement contributes to the submersibles stealthy characteristics. An additional hub and set of high-speed blades capable of generating a supercavity may be added to achieve supercavitation. The propulsion system can be varied to include a pumpjet and/or a centrifugal force blade system.

Abstract: The present invention relates to propulsion and hydraulic systems having a co-axial design wherein the inlet section, impeller section, and outlet section of a mixed flow pump system all have a common centerline axis or axis of rotation. The mixed flow pump system includes an outer casing and a central body disposed co-axially within the outer casing. A pump impeller is rotatably connected to the central body for imparting hydraulic energy to the fluid flowing through the mixed flow pump system. The mixed flow pump system may also include inlet flow conditioning vanes for conditioning an inlet flow of fluid to the mixed flow impeller for improving the cavitation performance and/or acoustic performance of the pump module. Stator vanes are provided for connecting the central body to the outer casing and to remove any swirl velocity from the fluid flow exiting the mixed flow pump impeller.

Abstract: A water jet propulsion unit including an intake section, a pump section having a pair of counter-rotating impellers mounted side by side on parallel driving shafts in separate cylindrical passages through the pump section and a mixing discharge section ending in a discharge nozzle. The mixing/discharge section is adapted to converge the flows of water discharge from the impellers to neutralise non-axial flow components from one impeller by non-axial flow components from the other impeller to maximise axial flow out of the mixing/discharge section. The unit may be operated as a high mass/low pressure unit or low mass/high pressure unit.

Abstract: A vessel propulsion system having a suction casing (4) configured with a suction inlet (4a) opening at a vessel bottom (1b), a suction flow path (4b) inclined to rearwardly ascend from the suction inlet (4a), and an impeller chamber (4c) formed horizontal, and disposed at a bottom of a stern, a delivery casing (10) connected to the suction casing (4) and submerged under a draft of the stern, and a set of forward and reverse rotatable axial flow blades (8) disposed in the impeller chamber (4c) of the suction casing (4).

Abstract: A water jet propulsion type outboard motor (1) which includes: a power source (2); a driving system; a housing (3); a curved tubular duct member (5); guide blades (22); and an impeller (14). The duct member (5) is fixed to the housing (3) on which the power source (2) is mounted, and having a suction port (9a) and a discharge port (11a). The guide blades (22) are provided within the duct member in the vicinity of the discharge port (11a) of the duct member (5). The impeller (14) is rotated by the driving system for transmitting a driving power of the power source (2), and has a spiral blade (20) with outer peripheral edge thereof close to an inner peripheral face of the duct member (5), and outer peripheral distal end portion thereof extending toward the suction port (9a).

Abstract: A screen system for marine thrusters having at least one constrictor for reducing exit jet cross-sectional area to increase exit jet velocity of a thruster.

Abstract: A reduced drag marine vessel providing a mechanism that will reduce or even eliminate the drag along the water-solid interface at the hull of the marine vessel. This mechanism is made up of a revolving elastic shell which is similar to a donut shaped belt. This belt forms an interior volume which houses rollers and a framework to support the tubular belt which can be further inflated with a gas to counter the hydraulic pressure of the water outside. Finally, this belt may be housed within a rigid outer tubular shell and contain a propeller within its center so as to form a marine nozzle.

Abstract: A vessel propulsion system having a suction casing (4) configured with a suction inlet (4a) opening at a vessel bottom (1b), a suction flow path (4b) inclined to rearwardly ascend from the suction inlet (4a), and an impeller chamber (4c) formed horizontal, and disposed at a bottom of a stern, a delivery casing (10) connected to the suction casing (4) and submerged under a draft of the stern, and a set of forward and reverse rotatable axial flow blades (8) disposed in the impeller chamber (4c) of the suction casing (4).

Abstract: A jet propelled watercraft having an improved extension assembly for dampening pulsations from the impeller of the jet propulsion unit and also an improved exhaust system having a separate idle discharge for permitting lower idle speeds without restriction of the idle exhaust gas flow.

Abstract: A jet propulsion system for an underwater vehicle, such as a submarine or torpedo is disclosed. The propulsion system includes a plurality of blades secured to a hub, in the front, which is rotated by a shaft connected to an engine through a transmission. A shroud surrounds the plurality of blades, and in combination with the body of the underwater vehicle, forms a nozzle through which flow is accelerated. The shroud is secured to the body of the underwater vehicle through a plurality of vanes. An additional hub including an additional set of blades may be secured to the underwater vehicle for additional thrust. The second hub may be located within the shroud. The inlet to the shroud may be covered with a screen mesh.

Abstract: The present invention having enhanced maneuverability that has hull at least partially submerged in fluid, which will ordinarily be water. The vehicle has a forward bow, a longitudinal axis extending rearwardly from said bow and opposed first and second sides. The first and second sides have respectively a first major opening and a first small opening and a second opening. A fluid-conducting tunnel extends generally transversely through the hull from the first major opening on the first side of the hull to the second major opening on the said side of the hull. There is a propeller for causing fluid to flow through the tunnel. In order to compensate for the detrimental effect on thrust (T) caused by increases in forward vehicle velocity (Vv), angular speed (N) of the propeller is increased proportionally to measured increases in axial fluid velocity (Vx).

Abstract: A jet propelled watercraft having an improved extension assembly for dampening pulsations from the impeller of the jet propulsion unit and also for mounting the jet propulsion unit. The structure simplifies the overall assembly and permits individual tuning with conventional units.

Abstract: An inlet grate mounted within the inlet channel of a watercraft, where the inlet grate contains a pivotally mounted divider vane disposed laterally across the inlet channel and biased by a torsional spring into a neutral position. The hydrodynamic forces of water moving through the grate alter the angle of the lateral vane, thus inducing equality of upper and lower inlet water volumes as well as pressure, proportionate to watercraft speed, thereby improving the efficiency of the watercraft's jet pump assembly without requiring the use of electromechanical devices.

Abstract: A water jet apparatus for propelling a boat. The water jet apparatus has a mechanism for adjusting the size of the outlet of the exit nozzle. The size of the outlet is increased to provide initial thrust and decreased for high speed. A smaller opening is also desirable for low-speed maneuvering. A cone made of resilient material is mounted to the stator hub. A hydraulically driven piston causes the resilient cone to elongate. This changes the shape of the cone and the position of the cone in relation to the exit nozzle outlet. When the resilient cone is elongated, the area of the exit nozzle outlet is decreased.

Abstract: A pump jet having a perforated wear liner inside the rotor housing for altering the spectrum of noise produced by the pump jet. The perforated wear liner is inserted in a circumferential recess formed on the inner surface of the rotor housing and surrounds the rotor tip region. The throughholes or perforations are preferably constant in size and regularly spaced. The perforated wear liner acts as a Helmholtz resonator liner which alters the spectrum of noise emitted from the pump jet during operation. Proper selection of the size, number and spacing of the holes permits the designer to control the specific noise spectrum range that is emitted from the front and rear lobes of the pump jet, thereby altering the hydrodynamic noise field.

Abstract: A boat or other water craft having an inboard engine, an outboard pump jet apparatus and a transom plate on which the pump jet apparatus is pivotably mounted. The boat hull bottom has a water tunnel formed therein, the transom plate has a tube portion in flow communication with the water tunnel, and the pump jet apparatus has an inlet which, in the operating position of the pump jet, is in flow communication with the tube portion of the transom plate. The pump jet apparatus is selectively pivotable between an operating position and a service position. In the service position the pump jet inlet is accessible to a boat occupant to clear debris from the pump jet inlet.

Abstract: This invention relates to marine jet drive systems and, more particularly to marine jet drive systems which include or are retrofitted with a preloader for reducing cavitation. The invention also relates to such a preloader which may be retrofitted to a standard marine jet drive system. The invention further relates to a method for reducing cavitation during operation of a marine jet drive system. The preloader comprises a water propelling device mounted on a shaft and rotatable within an intake housing of a marine jet drive unit ahead of and in axial alignment with the eye of the jet drive pump impeller whereby the water propelling device causes water to be drawn from the intake housing into the pump such that the pump impeller is preloaded with water across the eye of the impeller cavitation is reduced.

Abstract: An improved waterjet propulsor that uses differential static pressure from the water flowing through and around the propulsor to provide additional thrust via internal and external vanes. Uniform water velocity is also created by the vanes within the propulsor. A boat trimming system is incorporated as part of the waterjet discharge nozzle.

Abstract: An engine and pump assembly in which the pump has a water impermeable housing with a hollow cylindrical sleeve open at one end, and a plate mounted and sealed on the other end of the sleeve. The plate has an aperture disposed on the axis of the sleeve; and an engine is mounted on the housing with a drive shaft extending through the aperture in the plate coaxially with the sleeve. The sleeve has a port extending therethrough, and an elongated water impermeable hollow tube extends outwardly from the port to an open opposing end.

Abstract: A pump frame (7) is secured to a bottom (1b) of a ship in such a manner that a lower opening (19) is opened into water adjacent to a stern (1a) of the ship. A mixed flow pump (8) is secured to a frame (12) provided for the bottom (1b). A suction opening (26) of the mixed flow pump (8) is connected to a connection opening (17) in the upper portion of the pump frame (7). A discharge pipe (13) is connected to a discharge opening (27)) of the mixed flow pump (8). An impeller shaft (33) is horizontally extended in a pump casing (9) of the mixed flow pump (8). The impeller shaft (33) is provided with an impeller (11) for sucking and pressurizing water below the bottom (1b) through an introduction opening (19). Water pressurized by the impeller (11) is jetted to the rear of the stern through the discharge pipe (13) so that a ship (1) is propelled. The foregoing water jet propulsion apparatus (5) enables sucking performance free from cavitation and excellent propelling performance to be obtained.

Abstract: A jet propulsion system for a watercraft wherein the jet propulsion outer housing has the impeller shaft portion in which the impeller is journaled for rotation about an impeller shaft axis disposed at an angle to the discharge nozzle rather than concentric with it as previously utilized. This permits the appropriate trim angle for the discharge nozzle while, at the same time, permitting the engine to be mounted relatively high in the hull so as to afford adequate clearance on the underside of the engine for such things as increasing the oil capacity for four cycle wet sump engines are employed.

Abstract: A tunnel jet propulsion unit (11) for marine craft, wherein the passing water mass in the tunnel is converged by decreasing the cross-section flow area of the tunnel. The unit (11) comprises an intake section (1); an impeller section comprising a cylindrical housing (31), a rotatable hub (34) and a plurality of a radially spaced impeller blades (36); a diffuser section comprising an inwardly tapered inside surface (39), a fixed hub (38) and a plurality of radially spaced diffuser blades (40); discharge section (D); a bearing between the hubs (34) and (38); and means for rotating the rotatable hub (34). Additional features include anti-balling by-pass valve (172) positioned upstream from the impeller (33) to relieve excessive water pressure on the hull if unit (11) handling capcity is exceeded and a trim adjusting machanism in the discharge section (D) for adjusting the height of the unit outlet (30) with respect to the water surface.

Abstract: The instant invention describes an advanced marine propulsor that has a rotor that is, at least in its majority, enclosed by structure where the rotor receives water over at least a majority of its lower portions and gas over at least part of its upper portions. It is possible to delete the gas flow by use of one or more valves so that an approximate doubling of water flow rate occurs which is valuable as a thrust enhancer for low and mid-range marine vehicle speed operation. It is also possible to operate the rotor with water directed mainly to its lower portions but with little or no gas directed to its upper portions thus forming a partial vacuum over the upper portions of the rotor vanes. When used, a water directing valve that directs water to the rotor vanes preferably has a curvilinear water contacting surface so that water will adhere to and follow that surface. Use of port and starboard water directing valves allows varying levels of water flow to port and starboard sides of the rotor.

Abstract: An improved mounting arrangement for a twin jet propulsion unit eases the assembly of the system, as well as enhances the performance of the system. A unified mounting plate supports the propulsion units and offer a degree of adjustability which permits the propulsion units to be precisely aligned with desired longitudinal axes defined by the watercraft hull, as well as with each other. In addition, the rigidity provided by the mounting plates tends to hold the propulsion units, which cantilever rearward from the mounting plates, in the desired positions. As a result, additional support structure and fasteners can be removed from between the jet propulsion units and they can be spaced closer together so as to generally match a desired spacing between the inlet openings of the associated intake ducts.

Abstract: A jet propulsion system is provided for a water craft in which the secondary flow channel allows water to flow around the impeller region and bypass the impeller blades under certain conditions. The bypass feature provided by the secondary flow channel decreases static inlet pressure and improves the operation of the marine propulsion device at high speeds. In addition, the secondary flow channel increases the total mass flow of water through the steering rudder and therefore improves steering when the propulsion system is being rapidly decelerated, such as during sudden stopping conditions. The secondary flow channel can incorporate one or more individual conduits that bypass the impeller region of the propulsion system or, alternatively, can comprise an annular channel completely surrounding the impeller region.

Abstract: A water jet propulsion device for a vessel in which a suction inlet 4 is open at a vessel bottom part in a vicinity of a stern, water suctioned from the suction inlet 4 to a suction duct 5 is pressurized by a spiral blade 10 provided in an impeller housing 6, and jet water is ejected from an ejection duct 13 backward of the stern, and moreover, on an impeller shaft 7 provided in the impeller housing 6 are disposed a plurality of those spiral blades 10 with slipped phases, outer peripheral parts 10b of the spiral blades 10 are close to an inner circumferential surface of the impeller housing 6, and outer circumferential end parts 10c of the spiral blades 10 are extended to a suction side, and further in a fluid passage behind the spiral blades 10 are provided guide vanes 12, and cavitations and a rolling of a vessel body in a high-speed travelling are reduced, and a travel performance is improved.

Abstract: A boat propelling system is mounted in a water channel of the boat hull and composed of an engine, a transmission shaft driven by the engine, an impeller driven by the transmission shaft and provided with blades, a stator mounted behind the impeller and provided with stator vanes, and a nozzle located behind the stator. The impeller blades and the stator vanes are separated by a gap adjustable by the magnitude of jet flow of water.

Abstract: A jet drive unit is mounted within a jet propelled watercraft in a fashion which prevents vibrations due to the operation of the craft's impeller system from transmitting to the hull. The power transmitting shaft system connecting the water jet unit impeller with the craft's engine is made through an elastic, vibration dampening coupling. Further, the water jet unit casing is mounted to the hull through a plurality of vibration insulating connector assemblies. Thus undesirable hull vibration, and its accompanying noise, may be eliminated.

Abstract: A marine pump jet includes a rotor located upstream and in front of the rotor drive mechanism. The lower unit of the tractor pump jet has a rotor housing which substantially surrounds the rotor and a stator housing located downstream of the rotor and rotor housing. A drive shaft extending from an upper gear case enters the stator hub where a pinion gear engages a crown gear attached to the rotor shaft. This places the rotor drive mechanism downstream of the rotor so that the rotor is substantially the first mechanical element that water initially comes into contact with. The inlet opening of the pump jet is larger than the outlet opening at the outlet of the stator housing. Because the rotor operates on essentially undisturbed, non-turbulent water, it is more efficient than traditional pump jets where the rotor is located aft of the drive mechanism. The upper gear case includes a reverse shifting mechanism that permits the tractor pump jet to operate in either the forward or reverse direction.

Abstract: The present invention discloses a deflection member for draining, during the operation of a ship hull, an inlet channel (2) to a turned off water jet unit. The deflection member includes a flap (6) that is rotatably or shiftably attached to a bottom of a ship hull. The flap in disposed in front of or immediately in front of an inlet. When the flap is immersed, the flap creates a cavity (0) outside the inlet opening to cover the same.

Abstract: A marine propulsion system, incorporating a jet pump, provides improved mass flow through the pump by utilizing an inlet opening which initially diverges to a transition point in front of an impeller and then diverges from the transition point past the impeller region to the outlet opening of the pump. Significantly increased flow rates per horsepower are achieved by reducing the normal restrictions caused by the inlet and outlet openings of known pumps. A transmission is provided to connect the output shaft of an engine to the drive shaft of the impeller. Either a V-drive or a torpedo-type gear housing can be employed.

Abstract: An automatic trim control system for a marine jet drive adjusts trim in response to water pressure in the jet drive duct immediately upstream of the impeller. The preferred system includes a mechanical actuator consisting of a spring biased link rod mounted to a resilient diaphragm located in an actuator housing. The diaphragm separates the chamber within the housing into a front portion and a rear portion. The front portion of the housing communicates through a water pressure tap line with the water pressure in the jet drive duct immediately upstream of the impeller. When the watercraft is traveling at high speeds on plane, water pressure in the jet drive duct is sufficient to push the diaphragm rearward against the spring biasing force, thus positioning the jet drive in a trim-up position.

Abstract: A powerboat propelling system is composed of an engine, a water tract, a propeller, and a stator. The water tract is provided with a water inlet, a nozzle having a water outlet, and a midsection in which the propeller is mounted. The stator is composed of a frame, an axial portion, and a plurality of stator blades fastened with the frame and the axial portion. The axial portion has a front segment and a rear segment. The front segment and the frame form therebetween a first circular space forming a portion of the water tract, whereas the rear segment and the nozzle form therebetween a second circular space forming a portion of the water tract. The first and the second circular spaces have a cross-sectional area which becomes gradually smaller from one end thereof toward another end thereof contiguous to the nozzle for accelerating the flow of water in the water tract without increasing the length of the stator or nozzle.

Abstract: A motorboat propelling system is composed of a water current channel in which a propeller and a stator are located. The channel is provided at a head end thereof with a water inlet and at a tail end thereof with a propelling nozzle. The stator has an axial portion divided into a front section contiguous to the propeller and a rear section contiguous to the nozzle. The front section has an outer diameter becoming progressively smaller towards one end thereof contiguous to the propeller, whereas the rear section has an outer diameter becoming gradually smaller towards one end thereof contiguous to the propelling nozzle.

Abstract: The invention relates to a variable venturi for a watercraft vehicle or similarly powered vehicle which allows the operator of the vehicle to selectively choose to operate a watercraft vehicle for achieving maximum acceleration or, alternatively, maximum top end speed. The venturi is comprised of a collar surrounding the venturi adjacent to a distal end of the venturi. At such time as the collar is activated, exposing the water flow exiting the venturi to atmospheric pressure, the diameter of the water flow exiting the venturi is reduced by approximately 1.0 mm. to 1.5 mm. in radius. This slight change in the surface area of the water flow provides a lower mass flow of the exiting water with an increased velocity of the water and top speed of the vehicle. Alternatively, a larger diameter venturi provides a higher mass flow with a decreased velocity and maximum acceleration.

Abstract: A marine pump jet includes a rotor located upstream and in front of the rotor drive mechanism. The lower unit of the tractor pump jet has a rotor housing which substantially surrounds the rotor and a stator housing located downstream of the rotor and rotor housing. The drive shaft extending from the power head enters the stator hub where a pinion gear engages a crown gear attached to the rotor shaft. This places the rotor drive mechanism downstream of the rotor so that the rotor is substantially the first mechanical element that water initially comes into contact with. The inlet opening of the pump jet is larger than the outlet opening at the outlet of the stator housing. Because the rotor operates on essentially undisturbed, non-turbulent water, it is more efficient than traditional pump jets where the rotor is located aft of the drive mechanism. According to an alternative embodiment, a reverse shifting mechanism permits the tractor pump jet to operate in either the forward or reverse direction.

Abstract: The invention provides a water jet system with higher efficiency and better steering. The water jet system uses cantilever bars for an inlet grating, to prevent blockage. The water jet system also uses an elliptical impeller shaft housing to reduce turbulence and snagging of debris by the rotating impeller shaft. The water jet system uses impeller blades with a curved cross section that curves towards the direction of forward rotation. The water jet system uses U-shaped flanges mounted to the outlet of the water jet to provide steering.

Abstract: A jet drive cavitation control system briefly limits engine output power to prevent the onset of impeller cavitation when pressure upstream of the impeller indicates the likelihood of imminent impeller cavitation. The system uses a pressure sensor to sense water pressure, preferably immediately upstream of the impeller. The pressure sensor generates a signal that is transmitted to an electronic controller which controls the operation of the internal combustion engine that powers the jet drive. A threshold cavitation water pressure value is preselected at a point before the onset of impeller cavitation is likely. When the measured water pressure drops to or below the threshold cavitation water pressure value, the electronic controller immediately limits engine output to prevent impeller cavitation.

Abstract: The instant invention describes an advanced marine propulsor that has a rotor that is, at least in its majority, enclosed by structure where the rotor, in its preferred embodiment, receives water over at least a majority of its lower portions and gas over at least part of its upper portions. It is possible to delete the gas flow by use of a valve or structure so that an approximate doubling of water flow rate occurs which is valuable as a thrust enhancer for low and mid-range marine vehicle speed operation. It is also possible to operate the rotor with water directed mainly to its lower portions but with little or no gas directed to its upper portions thus forming a partial vacuum over the upper portions of the rotor vanes. When used, a water directing valve that directs water to the rotor vanes preferably has a curvilinear water contacting surface so that water will adhere to and follow that surface.

Abstract: A jet propulsion system for a personal watercraft provides a converging stator that can be manufactured using die-cast manufacturing techniques. The stator preferably has a stator housing having a substantially cylindrical inner surface, a stator hub, and seven equally spaced stator vanes supporting the hub coaxially in the stator housing. The cylindrical inside surface of the stator housing does not extend rearward as far as a conventional housing for a converging stator. The coaxial hub has a converging diameter portion that is located at least in part downstream or rearward of the stator housing. Rearward of the stator housing, the stator vanes extend from the stator hub to an outer free edge. With this configuration, a converging stator can be manufactured using aluminum die-cast manufacturing techniques.

Abstract: An apparatus is disclosed to alter the diameter of the nozzle of a jet boat, thereby allowing a user to maximize acceleration, top speed, fuel economy or other factors. The disclosed apparatus allows a user to adjust the nozzle diameter opening, while the boat is moving, by an elastic annular hydraulic bladder that reduces the cross sectional area of a cone formed by a plurality of cone plates. The apparatus is compatible with steering and trim adjustment devices, and is located rearward of them. The apparatus is also compatible with existing jet boat, and provides a bowl adapter that may be attached to the impeller bowl of an existing jet. A steering collar attaches to the bowl adapter by two vertical pins to allow rotation to the left and right. Two horizontal pins on the steering collar support a nozzle front lock plate in a manner that allows vertical trim adjustment. The nozzle cone plates are mounted in a hinged manner to the nozzle front lock plate and the nozzle housing support.

Abstract: An improved inlet duct for a marine jet propulsion system is disclosed designed to allow the overall system to operate more efficiently. The inlet duct includes a hydraulically efficient inlet tunnel with a forward entrance opening integrally formed on the bottom of the hull of the watercraft, and a rear exit opening formed inside the hull of the watercraft adjacent to the pump. The inlet tunnel is longitudinally aligned and gently curves upward inside said hull following streamlines of generation and has cross-sectional area that progressively increases from the fore to the aft positions therein. Disposed over the front entrance opening of the inlet tunnel is an articulating structure designed to adjust its size according to the difference in hydraulic conditions that exist inside the inlet tunnel and the outside of the hull so that the velocity of the incoming water matches the velocity of the watercraft in the body of water.

Abstract: A trim adjusting system for a small jet propelled personal watercraft. The trim is adjusted automatically in response to sensed water conditions which will indicate, among other things, the condition of the water flowing through the water inlet opening of the jet propulsion unit. The measured conditions may include water condition, watercraft speed and watercraft trim angle. The arrangement also permits manual operation and the permissible range of trim adjustment is less in manual operation than in automatic operation.

Abstract: An improved discharge nozzle and method for operating a marine jet propulsion system are disclosed designed to allow the pump to operate more efficiently. The discharge nozzle includes an outer nozzle structure mounted immediately downstream of the pump diffuser vanes which progressively reduces in diameter towards its rear exit opening. A needle is mounted within the diffuser hub and travels in axial alignment within the outer nozzle structure to adjust the effective opening of the discharge nozzle according to a pump affinity relationship, so that the pump is always operating at the most efficient head and flow for its current shaft RPM, regardless of boat speed or pressure recovery in the inlet duct.

Abstract: An improved water jet propulsion system for a jet propelled watercraft is disclosed designed to operate more efficiently. The improved propulsion system includes an adjustable water inlet duct, a larger pump, and an adjustable discharge nozzle. The inlet duct includes a hydraulically efficient inlet tunnel with an adjustable entrance opening which adjust in size according to the velocity of the water-craft in the body of water and the flow of water through the system. Using the inlet tunnel and the adjustable grate structure, the total dynamic head of the incoming water may be recovered at the pump. The pump is larger than typical pumps used on jet propulsion systems so that a greater flow of water at low head pressure may be delivered to the adjustable discharge nozzle. The adjustable feature on the discharge nozzle enables the flow through the system to be adjusted so that the hydraulic conditions on the pump are maintained at all boat speeds and all shaft rpm.

Abstract: Water jet propulsion unit for watercraft having a pump and stators arranged upstream and downstream of the pump for eliminating turbulence in the entering water and in the water jet generated by the pump, having coaxially arranged nozzles which are associated with the respective stator and are supported so as to be displaceable axially independently of one another, and having a switchable gear unit for driving the pump in the clockwise or counterclockwise direction in order to change the direction of motion of the watercraft, the water jet propulsion unit being supported at the watercraft so as to be swivelable by .+-.90.degree. approximately vertically to the axis of rotation of the pump rotor.

Abstract: A new method and apparatus for monitoring propulsion water flow in a water jet propulsion system that distinguishes propulsion system impairment from other potential causes of marine engine over-revving, allowing the accurate assessment of propulsion system function from a remote location, such as the vessel's instrument panel. This monitoring also prevents engine power loss, damage or failure and provides for the accurate assessment of propulsion system function from a remote location minimizing dangers arising from unmanned vessel operation and direct inspection of equipment. This marine propulsion system monitoring method and device, and a water craft pumping system monitoring method and device can both be monitored with the same display equipment, saving on the space and expense of two displays, one for each monitored system.

Abstract: A water jet propulsion unit intended for use in jet boats. The unit has an intake section, a pump section and a nozzle section. In the pump section there are two counter-rotating impellers on concentric counter-rotating shafts calibrated so that any radial flow created in the upstream impeller is converted into axial flow by the downstream impeller. In one embodiment the nozzle section has a throttled outlet to allow for a high mass/low pressure operation while maintaining pump priming. There are no support structures or stators downstream of the intake section in the preferred embodiment.

Abstract: A number of embodiments of jet-propelled watercraft embodying a combined jet propulsion unit and propulsion unit condition sensor. The condition sensor is contained within the outer housing of the jet propulsion unit and may be formed either in the grilled inlet opening, the water inlet portion, the straightening vane portion, or the discharge nozzle portion.

Abstract: A ride plate according to this invention is adapted to be attached to the bottom of the hull of a personal watercraft. It has a forward and a rearward axial orientation along a nominal axis of forward action of the craft. The ride plate includes a channel portion having a central portion and a pair of laterally spaced apart wall members which slant away from the central portion and from each other, thereby to form an intake chamber into which the intake port opens. The channel member is open at both ends to permit debris and excess water to leave the chamber, thereby constituting a minimized source of drag. An intake grate is incorporated into the ride plate at its forward end, having a pair of generally parallel legs, each preferably having a foil cross-section, and leaving between them, and on outside of the pair, open regions through which water can flow to the chamber.