Abstract: A watercraft includes an internal combustion engine mounted such that its crankshaft extends vertically. A gearbox is arranged beneath the engine and includes engine mounts attached directly thereto for mounting the engine to a mounting surface within the engine compartment. Thus, the engine may be mounted compactly arranged in the rear of the watercraft, thus minimizing the overall length of the engine compartment. Additionally, the engine mounts allow the engine to be mounted conveniently within a watercraft in a vertical orientation. The gear box may also include at least a portion of an exhaust conduit extending therethrough. The gear box may be also utilized as a lubricant reservoir for a lubrication system of the engine. Additionally, the exhaust conduit passing through the gear box may include a cooling jacket, thus protecting oil in the gear box from the heat emitted from the exhaust conduit therein.

Abstract: A rudder assembly for interfacing with a jet nozzle of a water jet propelled watercraft so as to thereby provide steering of the watercraft by pivoting of the jet nozzle even when a water jet is absent from the jet nozzle. A rudder is connected to a sleeve, wherein the sleeve is connected to the jet nozzle. In a first preferred form, the rudder extends in-line with, and immediately behind (aft of), the jet nozzle so as to be located in the water jet. In a second preferred form of the present invention, the rudder is notched adjacent the sleeve for accommodating movement of a thrust plate of a water jet propelled watercraft equipped with a thrust plate mechanism. Alternatively, the rudder may be located dependingly downward from the jet nozzle.

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: Presented is an improved marine vehicle propulsion system that utilizes a water accelerating rotor that operates efficiently when either partially or fully submerged all the while enclosed in a duct like a standard pump impeller pressurized nozzle waterjet. This new waterjet propulsor has a simple gas supply system without moving parts that supplies either gas or water to the water accelerating rotor dependent upon level of the waterline relative to the gas supply's inlet. One or more fluid inlet flow directing valve elements are offered that can vary the level of water reaching the rotor's inlet and can also, in an extended position, prevent water from impacting the waterjet's inlet. The latter item is valuable when the marine vehicle is either being towed or when it is being propelled by another propulsor as it reduces drag due to water flowing through an inoperative instant invention waterjet propulsor.

Abstract: A watercraft with a steer-responsive throttle generates thrust when the steerable propulsion unit is turned beyond a predetermined angular threshold. The turning of the steering wheel beyond the threshold causes the throttle to be opened so that the steerable propulsion unit produces a thrust at least equal to the minimal propulsive force needed to effectively steer the watercraft. A watercraft equipped with a steerresponsive throttle ensures that there is always sufficient thrust for steering the watercraft even when the operator fails to open the throttle manually. This steerresponsive throttle is applicable to single-engine personal watercraft, twin-engine jet boats or motorboats equipped with swivel-mounted outboard motors. In a first embodiment of the steer-responsive throttle, rotation of the steering wheel beyond the angular threshold causes an actuating cable to open the throttle.

Abstract: The present invention provides a propulsion system mounted in the hull of a marine vessel. The system includes a conduit system with water intake openings defined in the port and starboard portions of the hull adjacent the bow. Water intake conduits conduct water from the water intake openings to a collection chamber. Water discharge conduits conduct water from the collection chamber to water discharge openings. At least one impeller is mounted in each of said discharge conduits. A valve system is mounted in the conduit system and is selectively operable to isolate the system and prevent the flow of water through the system. A water pump may be used to evacuate water from the system when the valves are closed. A further preferred feature provides access to the impeller portion of the propulsion system. A conduit extension section diverges from the conduit system with one end above the level of the vessel's waterline. A sealable hatch is mounted to the conduit extension.

Abstract: A marine jet drive having a rotatable impeller, an impeller housing, an intake duct, a diffusor housing rearward of the impeller housing, an engine, and a unitary drive shaft extending from the engine to the impeller, and having a rear flexible coupling connecting the drive shaft to the impeller and a front flexible coupling connecting the drive shaft to the engine. Certain preferred embodiments include a shaft sleeve and rear seal assembly isolating the drive shaft from water and debris.

Abstract: The propulsion device (10) includes a housing (12) having an incoming end cap (14) and an outflowing end cap (16). A tubular bladder (20) within the housing is interconnected to each end cap, thereby varying the volume of both a chamber (22) within the bladder and a chamber (24) between the bladder and the housing during attractive or repulsive movement between end caps (14,16). Check valves control the flowthrough the end caps. The propulsion device is highly efficient and is able to move the vessel through water with little or no cavitation.

Abstract: A noise reducing system for a personal watercraft. The system includes a pump insulating system which insulates the pump housing from the hull. More particularly, the pump insulating system includes at least one insulating attachment for connecting a pump housing to a supporting surface of a personal watercraft. Such insulating attachment includes an insulator having a portion mounted between the pump housing and the supporting surface. Advantageously, the system also includes a resonator and a shield, both mounted on the exhaust system, and an insulating material mounted inside an air intake pipe.

Abstract: A jet powered boat may be provided with a water monitor for fire fighting purposes. The conduit for the monitor is connected to an opening through the bottom of the hull to draw water vertically from beneath the hull. Two motors are provided in the boat. One motor is configured to propel water through the monitor conduit to the water monitor. The other motor is configured to propel water through a propulsion jet at the rear of the boat. In one embodiment, a second propulsion jet is provided at the rear of the boat, connected to the conduit for the water monitor. A baffle at the intersection of the second propulsion jet and the monitor conduit may be operated to selectively direct water to either the monitor or the propulsion jet. In this embodiment, the two motors may be placed symmetrically on either side of the longitudinal centerline of the boat.

Abstract: A watercraft with a steer-responsive throttle generates thrust when the steerable propulsion unit is turned beyond a predetermined angular threshold. The turning of the steering wheel beyond the threshold causes the throttle to be opened so that the steerable propulsion unit produces a thrust at least equal to the minimal propulsive force needed to effectively steer the watercraft. A watercraft equipped with a steer-responsive throttle ensures that there is always sufficient thrust for steering the watercraft even when the operator fails to open the throttle manually. This steer-responsive throttle is applicable to single-engine personal watercraft, twin-engine jet boats or motorboats equipped with swivel-mounted outboard motors. In a first embodiment of the steer-responsive throttle, rotation of the steering wheel beyond the angular threshold causes an actuating cable to open the throttle.

Abstract: A four stroke internal combustion engine includes a cylinder head having a valve train having reduced profile that permits access to a spark plug assembly located therein.

Abstract: A tunnel thruster which is compact, quiet and can withstand the higher depth pressure encountered by a UUV. The UUV is usually a cylindrically shaped vessel and has a propulsor with control surfaces at one end. At two positions along the length of the body there are two cylindrical ports which pass through the body of the UUV. At each position one port is in the vertical plane while the other port is in the horizontal plane. These ports are four tunnel thrusters, which enable the maneuvering of the UUV. The tunnel thruster can be mounted in the ports of the UUV. The main components of the tunnel thruster includes a tunnel, motor assembly mounted in the tunnel, rotors on each end of the motor assembly and inlet ducts on each end of the tunnel. The tunnel thruster attempts to address the short comings of the commercial thrusters. The tunnel thruster is an all electrically powered thruster with all mechanical components contained within the tunnel. The rotors operate independently and are counter-rotating.

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: A jet-propelled water board for transporting a person upon water. The jet-propelled water board includes a board member having a top side and a bottom side, and also having a tapered front portion and a tapered back portion, and further having a plurality of water intake ports and water outtake ports being disposed through the bottom side of said board member; and also includes a fin being securely attached to the bottom side of the board member and on the back portion thereof; and further includes a jet propel assembly being disposed in the board member for forcing water through said the outtake ports.

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 marine vessel or watercraft in which the power plant or engine is cantilevered off of the inboard face of the transom by a mounting adapter. An inboard engine is attached to the mounting adapter. By this arrangement, the mounting adapter provides cantilevered support to the engine. The engine has at least one exhaust port for engine exhaust gases. The mounting adapter has an exhaust channel in flow communication with an exhaust port of the inboard engine. In addition, the transom has an opening in flow communication with the exhaust channel of the mounting adapter. Thus the passage in the mounting adapter provides a flow path for engine exhaust gases to pass through an opening in the hull. Optionally the exhaust channel in the mounting adapter includes a noise suppression device, e.g., a muffler.

Abstract: The present invention provides a watercraft having steering components (steering tabs or stabilizers) for maintaining steering capability even while amount of water ejected from a propulsion pump is decreased. The steering components are movably disposed on a hull of the watercraft at or below the water level on both right and left sides to be in an “Operating State” in which resistance of water is larger or to be in a “Non-operating State” in which the resistance of water is smaller in accordance with steering operation. Furthermore, a mechanism for absorbing an external force acting on the steering components in the “Operating State” is located in a system for operating the steering components. The mechanism reacts to the external force to allow the steering components to be transformed into the “Non-operating State.

Abstract: A water jet propelling type outboard motor (1) is provided with a casing member (50), a frame (10), a motor (11), a gear case (13), a vertical driving shaft (12), a horizontal following shaft (14), a power transmission mechanism (15), and an impeller (5). The casing member (51) has a front end water suction inlet (3a), a rear end jetting outlet (6a), a first inside space (51) extending from the suction inlet (3a) obliquely upward and rearward, and a second inside space (52) extending generally horizontally from a rear end of the first inside space (51) up tot he jetting outlet (6a). The frame (10) extends upwardly from the casing member (50) to be mounted on a ship body (2). The motor (11) is mounted on the frame (10). The gear case (13) is disposed laterally forward of the second inside space (52) and generally vertically above the water suction inlet (3a). The vertical driving shaft (12) extends from the motor (11) downward to be inserted into the gear case (13).

Abstract: A control mechanism for a watercraft is described herein said control mechanism comprising a steerable propulsion source, a steering controller for controlling said steerable propulsion source, a lid member connected to said steerable propulsion source, and at least one tab connected to said linking member, said at least one tab moveable between an inoperative position and an operative position whereby said at least one tab can be angled such that, in the operative position and when said watercraft is traveling upright in water in a substantially forward direction, a volume of water impinges on a top surface of said at least one tab thereby creating a downward and rearward force on said watercraft.

Abstract: A propulsion system for a watercraft is provided, which may be an integral part of a watercraft or may be retrofitted to a particular watercraft. The propulsion system is fixedly mounted to the hull in a central area, rather than along the perimeter of the watercraft. The propulsion system includes a jet-drive assembly coupled to a jet, an angular drive assembly for rotating the jet, and a control system for controlling the jet-drive assembly and the angular drive assembly.

Abstract: A Small Waterplane Area MultiHull vessel having an upper hull platform located above the design water line of the vessel which is maintained above the surface of a body of water by at least two cylindrical submerged hulls joined thereto by supporting struts. A buoyant core material is contained between inner and outer walls of the submerged hulls which define a cylindrical space in which a rotary propulsive means may be housed. In one embodiment, an engine means is situated on the upper hull platform and is joined to the rotary propulsive means through a work translating means which converts the output of the engine to rotary motion of the rotary propulsive means to provide a propulsive force.

Abstract: A water jet apparatus with counter-rotating impellers for propelling a boat. The impellers are coupled by an assembly comprising an impeller shaft secured to a first impeller and a gear train coupling the impeller shaft to a second impeller for counter-rotation. Preferably the gear train comprises one beveled gear secured to the impeller shaft, another beveled gear secured to the second impeller, and a beveled pinion meshed with the first and second beveled gears. The counter-rotating impellers can be driven by a drive shaft coupled to the first impeller for boats having an inboard motor or by a drive shaft coupled to the pinion for boats having an outboard motor.

Abstract: A transparent device that allows monitoring of the oil level and condition in the water jet propulsion system through means of a visual inspection. A layman can easily perform this inspection, simply by viewing the transparent thrust cone from the rear of the watercraft jet propulsion system, saving the expense and time of disassembly by a professional.

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: Several embodiments of personal watercraft having very compact construction, in particularly embodying a compact propulsion system wherein the engine and a number of its accessories all define a very compact area. A balance shaft is driven by the engine crankshaft for reducing the transmission of vibrations to the watercraft riders.

Abstract: A waterjet drive engine for the propulsion of large ships includes an elongated water conduit having a rearwardly directed exhaust portal, a forward extremity having a water intake portal, and a middle portion of larger diameter than the diameter of the exhaust portal. A hollow axially symmetrical chamber is centrally positioned within the middle portion, defining therewith an annular interstitial zone through which ambient water is caused to flow. A shaft driven by the ship's power system extends into the chamber and is provided with a circular array of propulsion blades positioned within the interstitial zone and adapted to force water rearwardly. A plurality of nozzles enter the chamber and direct high pressure steam toward the exhaust portal. The effect of the steam is to add an augmenting force to the rotative motion of the shaft.

Abstract: An immersed prime mover device, typically of some few cubic inches or feet in volume, cyclically vents accumulated compressed air, typically 10-200 P.S.I. and more typically 90-110 P.S.I. derived from air compressors or from storage tanks, forcibly eject a slug of water, thereby producing a propulsive force. The accumulation may be some few cubic inches per minute in a large reservoir to but cyclically occasionally or infrequently eject the slug of water, producing an intermittent propulsive force. The accumulation may be of some substantial portion of the volume of an accumulation reservoir every few seconds, frequently cyclically ejecting the slug of water to produce a nearly continuous propulsive force.

Abstract: A propulsion unit assembly for a personal watercraft provides for the quick and easy alignment of a propulsion device of the assembly relative to the longitudinal axis of the watercraft when mounting the propulsion device on the hull of the watercraft. The mounting arrangement includes a mounting plate having stoppers which cooperate with bosses formed on the front wall of the tunnel of the watercraft to properly align the mounting plate before fixing the plate to the hull and mounting the propulsion device thereto. In addition, the disclosed propulsion unit assembly includes an integrally formed cooling water supply system which utilizes the existing high-capacity jet pump unit to provide pressurized cooling water for cooling of the engine and associated watercraft components.

Abstract: A waterjet propulsion pump (14) is mounted in an opening in a fully submerged intermediate transom (12) located forward of the stern transom (11) and at the aft end of a dependent structural pod (15) on the hull bottom with the pump discharge nozzle (30) lying aft of the intermediate transom. A steering nozzle (50) is mounted on the discharge nozzle (30) for pivotal movement about an axis that lies in a vertical plane. At least one reversing deflector (100 or 300 and 400) is mounted for pivotal movement about an axis that is perpendicular to the vertical plane. A rotatable steering shaft (70, 270) operated by a steering actuator located with the hull (140 or 340) is coupled to the steering nozzle (50 or 250). A hollow reversing shaft (90, 290) is received telescopically over a portion of the steering shaft and is translatable axially relative to the steering shaft by a reversing actuator (150, 350) located within the vessel hull.

Abstract: An arrangement for mounting a water jet apparatus to a hull of a marine craft. The hull has generallly horizontal and vertical sections and sidewalls which define a cavity in which an inlet housing of the water jet apparatus is installed. The inlet housing has a top section which abuts an exterior surface of the horizontal hull section and a front section which abuts an exterior surface of the vertical hull section. A top mounting plate abuts an interior surface of the horizontal hull section, while a front plate abuts an interior surface of the vertical hull section. One set of fasteners hold the top mounting plate, the horizontal hull section and the top section of the inlet housing together. Another set of fasteners hold the front plate, the vertical hull section and the front section of the inlet housing together.

Abstract: An impeller for a water jet pump of a watercraft having a structure so as to enhance pump efficiency, and to reduce manufacturing cost having a tip portion configured to be fixed to a propeller shaft for being rotated integrally with the propeller shaft, and a rear end portion configured to be fixed to a pump shaft configured for being rotated in a pump casing. An upstream tip portion defines a spline hole which is formed directly in said tip portion of the impeller, the spline hole being configured for coupling to a spline shaft portion of the propeller shaft, the impeller further including a fitting hole which is formed on a rear end portion of the impeller configured for fitting a cylindrical member therein, and a cylindrical member is included having an outer periphery which can be fitted in the fitting hole and a female screw threads on an inner peripheral face configured for connection to the pump shaft are also provided.

Abstract: A mixed-flow type water jet pump having configured so that a tip clearance between an inner wall of a pump casing and an outer peripheral edge of an impeller can easily be adjusted, and which can easily be mounted on a watercraft. A pump casing is divided into two portions, a front casing and a rear casing, in a longitudinal direction, the front casing for housing an impeller provided with a longitudinal position defined simply with respect to the rear casing and being attached to the rear casing through a shim such that a predetermined clearance is formed between an inner wall of the front casing and an outer peripheral edge of the impeller.

Abstract: A pump jet in which the axial flow of water through the device is controlled by bleeding exhaust gas into the pump jet water stream, thereby producing a thrust loss. The addition of gas into the primary pump jet water flow stream reduces the effective flow density of the exit media, thereby reducing the exit momentum (and thrust) produced by the pump jet. The thrust modulation device can be actuated using any conventional electrical or mechanical actuation subsystem via a knob or lever positioned near the throttle control.

Abstract: A marine craft has with an inlet ramp, which increases in height as the inlet ramp extends rearward, and a cavity which communicates at its front with the rear of the inlet ramp. The cavity is open at its bottom and its rear. The marine craft is propelled by a jet pump apparatus having an inlet housing which is installed in the aforementioned hull cavity. The inlet housing defines an inlet volume in flow communication with the inlet ramp and a water tunnel in flow communication with the inlet volume. The inlet volume has a height which increases as it extends rearward. The inlet ramp and the inlet housing each have a lower U-shaped boundary, which boundaries are connected to form a generally rectangular inlet for water being sucked in by the water jet.

Abstract: In the propulsion arrangement for an axisymmetric vehicle described in the specification, four propulsion modules are removably mounted at the rear of a vehicle in symmetric disposition about the vehicle axis, each module having an inlet section at its forward end which draws in the vehicle hull boundary layer without separation from the vehicle hull and supplies it uniformly to a rotating blade section driven by a rim drive motor. Control vanes for the vehicle are mounted between adjacent pairs of propulsion modules.

Abstract: A watercraft having a speed measuring system which provides for accurate and consistent measurement of watercraft speed throughout the operation of the watercraft, including during violent maneuvers and/or sharp turns. The speed measuring system includes a ride plate assembly for a personal watercraft comprising a sensor and a plate. The sensor generally includes a moveable element and a housing supporting at least a portion of the moveable element. The plate includes a longitudinally-extending channel with the channel extending along at least a portion of the length of the plate. The housing is connected to an aft portion of the plate with at least a portion of the rotatable element being positioned in line with the channel.

Abstract: Several embodiments of personal watercraft employing exhaust systems that incorporate not only a catalyst, but also an exhaust silencing device for silencing the sounds of the exhaust gases. The components are laid out in such a way that there will be minimum heat transfer from the exhaust gases to the engine compartment, and also so that there will be a cooling air flow across the exhaust system to further provide this result. In one embodiment, the silencing device is mounted transversely at the front of the engine, and in other embodiments it is disposed longitudinally to the rear of the engine. In all embodiments, the components are laid out to maintain good fore and aft and side to side balance.

Abstract: Water jet ejection nozzles (2, 3, 4) different in ejection bore diameter or controllable of ejection bore diameter are arranged in a vertically spacing manner and fluid paths connected to the ejection nozzles are provided with open-close valves (6, 7, 8) to be individually controlled, or a water jet ejection nozzle (50; 60) having a controllable ejection bore diameter is vertically driven, for water jet propulsion to be in accordance with a varied draft position of a vessel.

Abstract: A water jet propulsion unit suitable for use in outboard or stern-drive configuration in motor boats. The unit has an intake section, a pump section and a drive section within which is incorporated a pressure control device and nozzle. In the pump section there are two counter-rotating impellers on concentric counter-rotating shafts. The impellers are mounted upstream of the drive section. The drive section contains a drive transmission carrier to which is attached the pressure control device both being located in the vortex created in the water flow, downstream of the two impellers. The pressure control device allows the propulsion unit to operate in a low pressure high mass mode while maintaining pump priming. The impellers can be removed without disassembly of the drive transmission carrier.

Abstract: It is an object to provide a reverser for a watercraft which has a high go astern efficiency and also functions as a side thruster while holding planing performance. In a reverser (1) for a watercraft in which a deflector (1A) is movably provided behind a pump nozzle of a water jet pump (P) to change the direction of water flow ejected rearward from the pump nozzle, thereby allowing the body (A) to go in reverse, a discharge port (1a) which directs the water flow in a transverse direction is provided on both side portions of the deflector (1A), thereby feeding the water flow from the discharge port (1a) along a transom (T) of the body (A).

Abstract: It is an object to provide a locking mechanism of a deflector for a watercraft which can perform the locking and unlocking operation of the locking mechanism simply by executing up-down movement of the deflector.

Abstract: A mounting structure for a water jet pump of a personal watercraft which includes a vertical wall 5 formed at the rear end of a water intake duct to form a pump mounting space 6, a pump bracket 8 fitted with an inlet of the water jet pump 7 and having a connecting surface 15 to sealingly connect to the vertical wall 5. A sealant recess 15b for accommodating a non-solid sealant S such as a silicon gel, is formed in the connecting surface 15 of the pump bracket 8, to enhance the air and water sealing quality between the connecting surfaces of the pump bracket 8 and the vertical wall 5.

Abstract: The inventive apparatus exercises control of the water flow which is discharged from a marine waterjet propulsor. Typical inventive embodiments comprise plural horizontal and plural vertical blade-like structures which together describe an open-ended, box-like rectilinear configuration characterized by at least two adjacent channels. Every vertical blade-like structure includes, at its aft end, a “steering” flap which is pivotable about a vertical axis. Some inventive embodiments advance marine craft reversing by implementing one or more bucket-like devices behind the inventive apparatus.

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 jet powered boat may be provided with a water monitor for fire fighting purposes. The conduit for the monitor is connected to an opening through the bottom of the hull to draw water vertically from beneath the hull. Two motors are provided in the boat. One motor is configured to propel water through the monitor conduit to the water monitor. The other motor is configured to propel water through a propulsion jet at the rear of the boat. In one embodiment, a second propulsion jet is provided at the rear of the boat, connected to the conduit for the water monitor. A baffle at the intersection of the second propulsion jet and the monitor conduit may be operated to selectively direct water to either the monitor or the propulsion jet. In this embodiment, the two motors may be placed symmetrically on either side of the longitudinal centerline of the boat.

Abstract: A marine vehicle having enhanced maneuverability, which has a hull at least partially submerged in water. The vehicle has a forward bow, a longitudl 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 major opening and a second small opening. The small openings are positioned rearwardly of the first small opening. A major water conducting tunnel extending 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 water to flow through the tunnel. A small water conducting system extends between the first small opening on the first side of the hull to the second small opening on the second side of the hull.

Abstract: A watercraft includes a monitoring and control system to sense the operational state of a catalytic device and a cooling system used with an exhaust system of the watercraft. The monitoring and control system includes a collection port formed downstream of the catalytic device. During diagnostic testing of the engine and the catalytic device, a collection element is inserted into the collection port. A plug, however, normally closes the collection port during normal engine operation. A cover extends over the collection port and a substantial portion of the surrounding exhaust pipe. The cover, or at least a portion thereof, is readily removable so as to provide access to the collection port. The exhaust system also includes a water trap located downstream of the collection port. A foam core support member supports the water trap within a hull of the watercraft, with an insulator positioned between the support member and the water trap.

Abstract: A simple and efficient reverse propulsion and control means for water jet powered boats which includes a sliding water valve for controlling exhaust thrusters mounted around the peripheral of the boat and which is coordinated with pivotal movement of the main thruster nozzle.