Abstract: Provided is a twin-skeg ship that allows for a further improvement in propulsion performance (propulsion efficiency). A twin-skeg ship (10) having a pair of left and right skegs (3) on the bottom (2) of a stern has reaction fins 5, each comprising a plurality of fins 5a extending radially from a bossing (6) fixed to a stern frame (7) provided at a rear end of the skeg (3), or from a fin boss provided on the bossing (6), in a range where a flow immediately in front of a propeller (4) attached to the skeg (3) with a propeller shaft (4a) therebetween has a component in the same direction as a rotational direction of the propeller (4).

Abstract: An apparatus for providing thrust adjustment on an underwater vehicle with a propeller shroud is disclosed. A portion of the vehicles body is provided with a compliant surface such that expansion and contraction of the compliant surface affects the flow of water through a channel formed by the vehicle body and the propeller shroud, resulting in variable thrust on the vehicle.

Abstract: A flow control mechanism, for improving pressure resistance and hull vibration, includes a lower fin and an upper fin. The lower fin is disposed between a second station and a fourth station in a length direction of a ship and between 10% and 20% of a design draft from a bottom of the ship in a height direction of the ship, the lower fin being inclined at an angle of 20 to 40 degrees with respect to a design draught (or base) line. The upper fin is disposed between the second station and the fourth station in the length direction of the ship and between 30% and 60% of the design draft from the bottom of the ship in the height direction of the ship, the upper fin being inclined at an angle of 10 to 30 degrees with respect to the design draught (or base) line.

Abstract: An aeration control system and method for a marine vessel. The system includes a valve configured to be coupled to an aeration conduit of a marine vessel. The valve is configured to be responsive to a valve control signal having a first value so as to be open and to provide air to the aeration conduit, and the valve configured to be responsive to the valve control signal having a second value so as to be closed and not provide air to the aeration conduit.

Abstract: A water flow limiting system for a boat with a propeller shaft and a propeller including a water flow limiting plane and a mechanism. The water flow limiting plane is provided for positioning below the propeller shaft and forward of the propeller for limiting water flow to the propeller. The mechanism is provided for steering the water flow limiting plane relative to the boat. If the propeller shaft is steerable relative to the boat, the mechanism may be a mounting mechanism which maintains the flow limiting plane generally aligned with the propeller shaft. The mechanism may be a steering mechanism which steers the flow limiting plane relative to the propeller shaft. A bite ram may be included for controlling vertical displacement of the flow limiting plane relative to the propeller shaft. The mechanism may be a mounting mechanism for mounting the flow limiting plane to a propeller shaft carrier.

Abstract: A combined hull and steering mechanism for a marine vessel has a substantially rectangularly-shaped upper hull joined to a lower hull that is dual-tapered from its sidewalls to both its forward and aft portions. A directional thrust steering mechanism having a pair of vertical rudder blades positioned on either side of a conventional propeller extending from the centerline of the lower hull directs the water from the propeller, thus enabling the vessel to move more efficiently and with greater maneuverability in both forward and reverse directions. The dual-tapered hull permits a significantly better flow of water to and from the propeller and steering mechanism of the vessel, particularly when operating in reverse, thereby allowing the vessel to turn 360° in its own length.

Abstract: A boat stabilizer that is attachable to the anti-cavitation plate or other structure of the lower drive unit of a boat motor without permanently modifying the structure of the anti-cavitation plate or other structure is provided. The shape and size of the boat stabilizer causes the stabilizer to effectively harness and control the thrust energy generated by the propeller resulting in improved thrust and fuel efficiency. Due to various features, the drag associated with the boat stabilizer is kept to a minimum. Finally, decals and other decorative elements are integrally embedded into the top surface of the inventive boat stabilizer using in-mold decoration (“IMD”) technology which makes the elements resistant to ultra-violet light, virtually indestructible and highly appealing. A boat motor, a method of attaching a boat stabilizer to a boat motor and a method of molding a boat stabilizer having at least one decorative element integrally embedded in the top surface thereof are also provided.

Abstract: A marine propulsion apparatus includes an anti-cavitation plate on a casing that supports a propeller. A lift generation plate, which generates lift during propulsion, is disposed at a position rearward of the casing and above the anti-cavitation plate and extends in a width direction of a hull. The lift generation plate is mounted on the casing via a stay.

Abstract: A passive air induction system for boats that includes a wedge member and air induction tubes. The system is installed within the propeller tunnel of high-speed planing vessels to reduce or eliminate noise and vibration caused by cavitation vortices created by rotation of the propeller blades. The air induction tubes include air inlets that receive ambient air, which is delivered to the wedge member to be released from a plurality of distribution slots on the wedge member as air bubbles. The air bubbles released from the distribution slots provide a cushioning effect against contact between the cavitation vortices and the vessel hull, thereby reducing vibration and noise that has been heretofore common at high speeds in planing vessels.

Abstract: A combined hull and steering mechanism for a marine vessel has a substantially rectangularly-shaped upper hull joined to a lower hull that is dual-tapered from its sidewalls to both its forward and aft portions. A directional thrust steering mechanism having a pair of vertical rudder blades positioned on either side of a conventional propeller extending from the centerline of the lower hull directs the water from the propeller, thus enabling the vessel to move more efficiently and with greater maneuverability in both forward and reverse directions. The dual-tapered hull permits a significantly better flow of water to and from the propeller and steering mechanism of the vessel, particularly when operating in reverse, thereby allowing the vessel to turn 360° in its own length.

Abstract: A marine drive system (1) with a partially submerged propeller located at the transom of a boat comprising, for each propeller (2), a forward-opened shroud (20), positioned above the propeller (2), such as to define, between it and the water level, a channel (23) extending longitudinally and having, at the propeller (2), a cross-section whose area decreases from the transom (30).

Abstract: A method and apparatus is directed towards an advanced blade section for propellers that allow watercrafts to effectively travel in both sub-cavitating and super-cavitating modes. The advanced blade section includes a streamlined profile having a convex upper surface and a lower surface that includes both a convex portion and a concave portion. When the propellers are rotated in a first direction at low speeds to propel the watercraft in the forward direction, the advanced blade section experiences a fully wetted flow over both the upper and lower surfaces at low speeds. At high speeds, the advanced blade section experiences a partially wetted flow, with only a front part of the lower surface being fully wetted, at high speeds. When the propellers are rotated in a second direction opposite the first direction to reduce the speed of the watercraft, the blade section experiences a substantially wetted flow over both upper and lower surfaces.

Abstract: A marine propulsion apparatus includes an anti-cavitation plate on a casing that supports a propeller. A lift generation plate, which generates lift during propulsion, is disposed at a position rearward of the casing and above the anti-cavitation plate and extends in a width direction of a hull. The lift generation plate is mounted on the casing via a stay.

Abstract: A boat hull comprises a hull body having two lateral flanks linked by a bottom surface, and at least two propulsion compartments provided in two bulges protruding below the bottom surface of the hull body. Each propulsion compartment lodges a propulsion engine located below the bottom surface of the hull body. The propulsion engines are located at the deepest position in the hull and below the water plane.

Abstract: A shrouded outdrive propels a high-speed boat having a hull for high-speed passage through water. The hull has at least one bow at the forward end and at least one transom at the stern. A tubular shaft extends at a small angle (6° to 12°) from the boat transom into the water, and a drive shaft is arranged within the tubular shaft. A propeller is mounted to the drive shaft for partial immersion in the water so that a lower portion of the propeller extends into the water during high-speed floating passage of the boat and a upper portion of the propeller is above the water during high-speed floating passage of the boat. A shroud is arranged about the propeller and is disposed below the water and adjacent the propeller. A mount holds the shroud to form a shroud-enclosed channel during high-speed passage of the boat through the water in which the propeller rotates.

Abstract: An apparatus is disclosed for improving safety and hydro-flow thrust from a trolling motor. The apparatus may include a first and second semi-circular portions configured to connect together to substantially enclose a hydro-drive device, and a semi-circular bracket coupled to each semi-circular portion, the semi-circular brackets together capable of fixedly coupling the first and second semi-circular portions to a trolling motor housing. The apparatus may also include an annular portion configured to couple to an aft opening formed by the first and second semi-circular portions.

Abstract: A stern unit of marine craft that comprises a casing, a propeller, a propeller shaft, and at least one rudder actuated by hydraulic pistons is described. The casing is open at the bottom, with its bottom surface having a parabolic shape in cross-section. The casing has an inlet section near to the hull that diverges rearwardly toward an outlet section. The casing provides a housing to the shaft, the propeller, and the rudders, with a gap located above the trace line of the boat bottom where air is sucked above the water surface line such that an air film extends inside the casing along the bottom surface of the casing to an outlet of the casing. The air film reduces frictional resistance between the flowing water and the casing surface to enable additional thrust.

Abstract: A prop wash straightening apparatus for increasing the efficiency of propeller-driven watercraft. An elongated outer tubular member open at each end thereof is adapted for connection to the boat or vessel to position said outer member immediately downstream of the propeller and in substantially longitudinal fixed alignment with the direction of axial thrust produced by the propeller. A plurality of elongated hollow open-ended inner tubular members are positioned in closely packed fashion within, and generally coextensive with a substantial portion of the length of the outer tubular member. A proximal or forwardly end of the inner tubular members is positioned in close proximity to a trailing plane of the propeller. The outer tubular member extends from the proximal end of the inner tubular members to surround the blade tips of the propeller to direct substantially all prop wash from the propeller into the inner tubular members.

Abstract: The invention is a lower housing unit and propeller protection assembly for a boat motor. The assembly comprises a planar clamp member, securable to a boat motor upper housing unit. An adjustable length, linear connector member is secured at one end to the clamp member, with the linear connecting member positioned forward of a boat motor lower unit housing and propeller. A propeller and lower unit protection subassembly is secured to the lower unit's skeg and to an end of the linear connector member, which is opposite the clamp member. A reinforcing member is secured to the linear connector member and extends to the lower unit protection subassembly. The protection assembly transfers impact force on the subassembly and reinforcing member to the clamp member.

Abstract: In a watercraft drive for a watercraft having front and rear propellers respectively mounted on a drive shaft in coaxial longitudinally displaced relationship, each of said propellers having at least two blades, the front and rear propellers having equal diameters and being driven at like rotational velocities. The central portion of the rear propeller up to a diameter equal to the diameter of the water jet arriving at the rear propeller, which due to the action of the front propeller has a contracted cross section, is designed to optimize the jet energy exiting the front propeller. The rear propeller has an annular area extending from the central portion to the outer circumference of the rear propeller, being designed with the same design as characterizes the front propeller. The annular area of the rear propeller receives a flow of surrounding ambient water.

Abstract: A course-holding, high-speed, sea-going vessel having a hull which is intended to hold payloads or passengers and at least one rotatable, preferably electric, rudder propeller (POD) which is arranged gondola-like under the hull of the vessel and has, to supply it with power, at least one motor/generator unit which is arranged in the hull of the vessel, the hull of the vessel having at least in part a bottom which rises somewhat toward the two sides of the hull, and in that the front part of the hull is designed so as to stabilize the course and movement of the vessel and ending under water, in particular in a relatively slender bow with a bulb, and in that a flow-guiding element (skegg) is arranged upstream of each rudder propeller in order both to optimize the handling characteristics and to achieve an optimized flow against the rudder propeller, which has a displacement volume for the water flowing against the respective rudder propeller.

Abstract: Hull and propeller arrangement for a surface watercraft (1), provided with at least one propeller (3), in addition to which the propeller (3), at high speeds of the watercraft, is surface-piercing, and the propeller (3) is arranged in such a manner that only the propeller blades (11) or parts thereof are submerged in the water at high speeds of the watercraft (1), in addition to which the hull (2) is provided with at least one streamlined projecting part (4) extends essentially in the longitudinal direction of the hull (2), the projecting part (4), in terms of its outer shape, has, at its aft end (6), an end edge (15) which, at least in part, extends essentially transversely to the longitudinal direction of the projecting part (4), the propeller (3) is locaded immediately astern of the end edge (15), and a part of the propeller, in the radial direction, extends beyond the delimiting surfaces of the projecting part (4).

Abstract: A line cutting device for use with a hydrodynamic propeller has a blade (5) fixed to a vessel having the propeller. Three rotating blades (22) extend from a hub fixed around the propeller's shaft. The fixed and rotating blades are arranged for line shearing action. Each of the rotating blades has four apertures (21) extending from front to back through the blade for passage of water therethrough towards a respective blade of the propeller. The apertures are arranged to alleviate cavitation on the propeller blades.

Abstract: In a watercraft drive for a watercraft having front and rear propellers respectively mounted on a drive shaft in coaxial longitudinally displaced relationship, each of said propellers having at least two blades, the front and rear propellers having equal diameters and being driven at like rotational velocities. The central portion of the rear propeller up to a diameter equal to the diameter of the water jet arriving at the rear propeller, which due to the action of the front propeller has a contracted cross section, is designed to optimize the jet energy exiting the front propeller. The rear propeller has an annular area extending from the central portion to the outer circumference of the rear propeller, being designed with the same design as characterizes the front propeller. The annular area of the rear propeller receives a flow of surrounding ambient water.

Abstract: A dualistic stern-appendant device comprises, in integrated form, at least two gate-supportive bodies and at least one flap-hydrodynamic body. The device is characterized by an alternating arrangement of bodies (totaling an odd number of at least three bodies) whereby no two consecutive gate-supportive bodies are next to each other and no two consecutive flap-hydrodynamic bodies are next to each other. Each gate-supportive body has an upper surface which is a gate-supportive surface, all of the gate-support surfaces together representing a cumulative gate-supportive surface. Each flap-hydrodynamic body has a lower surface which is a flap-hydrodynamic surface, all of the flap-hydrodynamic surfaces together representing a cumulative flap-hydrodynamic surface. The geometric plane defined by the cumulative gate-support surface is not encroached upon by any flap-hydrodynamic body.

Abstract: A thruster for use in underwater applications, including a stator assembly having an encapsulated set of coils and a rotor assembly having an encapsulated set of permanent magnets. Two ring-shaped rotor bearings, incorporating both thrust bearing surfaces and journal bearing surfaces, are mounted on the rotor assembly, for bearing engagement with corresponding bearing surfaces of ring-shaped bearing assemblies mounted on the stator assembly. The rotor bearings include radial grooves that form a centrifugal pump for drawing sea water through a filter assembly, which then directs the filtered water past the stator coils, for cooling, and past the bearing surfaces, for cooling and lubrication. The stator bearing assemblies are made up of a number of arc-shaped segmental bearings having specially configured cantilevered arms that facilitate the creation of a lubricating film of filtered sea water between the bearing surfaces.

Abstract: An inboard propeller drive system for shallow water boats comprising a stern tunnel and a propeller drive shaft sub-assembly. The tunnel protrudes upwardly from the floor of the boat, and has an S-shaped bottom plate immersed in water. The sub-assembly includes a housed drive shaft, a propeller, a cavitation plate, and a steering mechanism. The forward end of the sub-assembly is pivotally mounted on opposing inner walls of the tunnel. A universal joint connects the forward end of the drive shaft to the output shaft of an inboard engine. A control shaft extends from the forward end of the sub-assembly to the exterior of the tunnel. The control shaft may be rotated by a user-controlled actuator to raise and lower the sub-assembly, thereby pre-determining the depth of the propeller. Encounters with submerged objects may also cause the sub-assembly to rotate upwardly to prevent propeller damage.

Abstract: A propulsion apparatus for a vessel includes a main screw and a push type POD propeller which is provided rearward of the main screw. Furthermore, a plurality of grooves which extend along flow directions of a hub vortex generated by the main screw are provided on a front end portion of a casing of the POD propeller. According to this propulsion apparatus for a vessel, the hub vortex generated by the main screw rearward of the main screw is weakened by diffusing the hub vortex along the grooves, and therefore the propulsion efficiency of the propulsion apparatus for a vessel is improved.

Abstract: A boat propulsion system includes a boat (52, 52′, 152, 152′) having an elongated hull (54, 54′, 154, 154′) with a water flow channel (56, 56A, 56B, 156A, 156B) formed in the bottom thereof, wherein a movable trim plate (68, 68A, 68B, 178A, 178B) is disposed within the water flow channel (56, 56A, 56B, 156A, 156B) for controlling a flow of water to a surface-piercing propeller (76, 76A, 76B, 176A, 176B) which is positioned aft of the water flow channel (56, 56A, 56B, 156A, 156B) and which is disposed within a propeller cavity (170, 170A, 170B) formed in the bottom of the hull (54, 54′, 154, 154′). In a fully extended position, the trim plate (68, 68A, 68B, 178A, 178B) is flush with the hull of the boat, and in a fully recessed position the trim plate (68, 68A, 68B, 178A, 178B) is completely recessed within the water flow channel (56, 56A, 56B, 156A, 156B).

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: A vane structure for a propeller for engaging fluid and preventing cavitation or the rapid formation and collapse of low-pressure gas bubbles in a liquid. The vane structure for a propeller includes a plurality of spaced vanes that are mounted to and extend away from a hub. Each of the vanes has a leading edge, a trailing edge and an end. A lip is mounted on the end of each of the vanes for selectively engaging fluid and dispersing low-pressure gas bubbles positioned generally adjacent to the plurality of spaced vanes.

Abstract: A thruster for use in underwater applications, including a stator assembly having an encapsulated set of coils and a rotor assembly having an encapsulated set of permanent magnets. Two ring-shaped rotor bearings, incorporating both thrust bearing surfaces and journal bearing surfaces, are mounted on the rotor assembly, for bearing engagement with corresponding bearing surfaces of ring-shaped bearing assemblies mounted on the stator assembly. The rotor bearings include radial grooves that form a centrifugal pump for drawing sea water through a filter assembly, which then directs the filtered water past the stator coils, for cooling, and past the bearing surfaces, for cooling and lubrication. The stator bearing assemblies are made up of a number of arc-shaped segmental bearings having specially configured cantilevered arms that facilitate the creation of a lubricating film of filtered sea water between the bearing surfaces.

Abstract: Hull and propeller arrangement for a surface watercraft (1), provided with at least one propeller (3), in addition to which the propeller (3), at high speeds of the watercraft, is surface-piercing, and the propeller (3) is arranged in such a manner that only the propeller blades (11) or parts thereof are submerged in the water at high speeds of the watercraft (1), in addition to which the hull (2) is provided with at least one streamlined projecting part (4) extends essentially in the longitudinal direction of the hull (2), the projecting part (4), in terms of its outer shape, has, at its aft end (6), an end edge (15) which, at least in part, extends essentially transversely to the longitudinal direction of the projecting part (4), the propeller (3) is locaded immediately astern of the end edge (15), and a part of the propeller, in the radial direction, extends beyond the delimiting surfaces of the projecting part (4).

Abstract: An outboard motor which includes a driving motor, a switching device (13), an impeller (15) and a blade casing (8). The switching device (13) switches rotation of a drive shaft (12) of the driving motor between normal and reverse directions. The impeller (15) is rotated with a driven shaft (14) connected to the switching device (13). The blade casing (8) includes a first duct member (19a) and a second duct member (20a). The first duct member (19a) has a first opening (18) through which water is sucked from the outside when the impeller (15) is rotated in the normal direction. The second duct member (20a) connected to the first duct member (19a) encloses the impeller (15), and has a second opening (21) through which water is sucked from the outside when the impeller (15) is rotated in the reverse direction.

Abstract: The present invention, in one form, is a skeg having an airfoil shape which facilitates maintaining engine control even at high speed but does not adversely affect engine performance. In one embodiment, the skeg includes a fore end, an aft end, and opposing sidewalls extending from the fore end and the aft end. One sidewall includes a camber, or curved surface, and the outer surface of the other sidewall is flat, or planar.

Abstract: The propulsion apparatus for a vessel comprises a main screw and a push type POD propeller which is provided rearward of the main screw. Furthermore, a plurality of grooves which extend along flow directions of a hub vortex generated by the main screw, are provided on a front end portion of a casing of the POD propeller. According to this propulsion apparatus for a vessel, the hub vortex generated by the main screw rearward of the main screw is weakened by diffusing the hub vortex along the grooves, and therefore, the propulsion efficiency of the propulsion apparatus for a vessel is improved.

Abstract: A bottom assembly for motor boats is described, of the type including at least one longitudinal tunnel, through which passes a propeller shaft exiting from the bottom, wherein there is provided at least one ground wall to close, totally or partially, the tunnel and limit the entry of water into the same during boat advancement.

Abstract: The present invention pertains to a device for changing the direction of travel of a watercraft with a drive with a gondola-like underwater housing 2 having a contour favorable in terms of flow outside the hull 1 of the watercraft, past which water flows and which is connected to the hull 1 of the watercraft by a shaft 3, one end of which is associated with the underwater housing and the other end of which is associated with the hull 1 of the watercraft. A drive shaft 7, which carries at least one propeller 6 outside the underwater housing, is led out of at least one end of the gondola-like underwater housing 2. The change in the direction of travel of the watercraft 1 is brought about by the shaft 3 being mounted at its upper end pivotably on the watercraft 1 and by a pivoting motor 24 (toothed ring 20, motor pinion 21) acting on the shaft.

Abstract: A bottom assembly for motor boats is described, of the type including at least one longitudinal tunnel, through which passes a propeller shaft exiting from the bottom, wherein it is provided at least one ground wall to close, totally or partially, the tunnel and limit the entry of water into the same during boat advancement.

Abstract: The present invention pertains to a device for changing the direction of travel of a watercraft with a drive with a gondola-like underwater housing 2 having a contour favorable in terms of flow outside the hull 1 of the watercraft, past which water flows and which is connected to the hull 1 of the watercraft by a shaft 3, one end of which is associated with the underwater housing and the other end of which is associated with the hull 1 of the watercraft. A drive shaft 7, which carries at least one propeller 6 outside the underwater housing, is led out of at least one end of the gondola-like underwater housing 2. The change in the direction of travel of the watercraft 1 is brought about by the shaft 3 being mounted at its upper end pivotably on the watercraft 1 and by a pivoting motor 24 (toothed ring 20, motor pinion 21) acting on the shaft.

Abstract: A propulsion system for a water craft having at least one shaft extending rearwardly form the transom of the hull of the craft and a drive system for driving the at least one shaft. A surface piercing propeller is mounted on the at least one shaft, proximal to the trailing edge of the hull, so that the propeller operates in a transom cavity created behind the hull, in use of the craft. The ratio (S/C) of the spacing of the blades to the blade cord for each propeller is at least 2.0 along substantially the whole length of the blades. The propulsion system has a high operational efficiency particularly suited for high speed marine craft.

Abstract: Dual propeller propulsion system for water crafts having two propellers (3, 4) fitted in the same axis outside the ends of an underwater housing (2) configured as a gondola so as to facilitate flow, said housing being placed under the hull of the water craft having a driving mechanism lodged in the underwater housing for both propellers (3, 4) to which the energy coming out for both propellers (3, 4) to which the energy coming out of the hull of the water craft is guided by means of a housing shank (18), one of the ends of which is mounted on the hull (24) of the water craft while the other is mounted in the underwater housing (2).

Abstract: A pump-jet type of outboard propulsion unit within a surrounding fluid mem for marine craft or the like, is protectively enclosed within cylindrical shrouding which forms an axial flow passage about the exhaust channel of the propulsion unit through which flow of the fluid medium is induced by rotation of impeller blades. Inflow of the fluid medium to the flow passage is modified at an inlet end of the shrouding by a plurality of angularly spaced vanes attached thereto and extending forwardly therefrom at an angle.

Abstract: A lift-generating device for a power boat includes a boundary (4) of semi-circular form in cross section mounted beneath the propeller (5) of the boat so that the propeller (5) produces a high-speed water flow over the upwardly facing surface of the boundary (4), thereby creating lift.

Abstract: A detachable hydro-planing foil for a marine outboard propeller drive comprises a plate having leading edges that are substantially backswept symmetrically from a plate centerline and trailing edges that are arced in a forward concavity substantially symmetrically from the centerline. Laterally of the centerline, the plate terminates with plate tips that are down turned with a negative dihedral of between about 25.degree. and about 45.degree.. The forward concavity of the trailing edges sweeps the trailing edge forward of the forward propeller rotational plane.

Abstract: A marine outboard drive that is equipped with integrated splash plates and a baffle plate that prevent water splash-up along the drive shaft housing. The baffle plate protrudes from the drive shaft housing to interact with plates on the lower bracket to create a labyrinth effect. The labyrinth created by the splash and baffle plates impedes the path of any water impinging upon the lower bracket and the drive shaft housing. This minimizes the amount of water travelling up the drive shaft housing. A splash plate may also be included on the lower bracket to minimize water flow above the lower bracket.

Abstract: A thrust enhancer includes a peripheral ring with an exhaust ring concentrically supported within the peripheral ring by a plurality of radially extending circumferentially spaced struts. Each strut carries a blade that is preferably angled in the left-hand direction at about a 36.degree. angle with respect to a plane defined by the strut to redirect water flowing at lateral angles with respect to the axis of the propeller shaft so that the water moves more in alignment with the propeller shaft to cause the thrust forces caused by rotation of the propeller to be directed more completely aligned with the axis of the propeller shaft. Suitable brackets are provided for securely mounting the thrust enhancer onto an outboard motor housing or other mounting location aft of a marine propulsion propeller.

Abstract: A hydrofoil stabilizer for a marine motor includes a hydrofoil wing having a generally planar configuration and a shroud member affixed to an underside of the hydrofoil wing. The shroud member has a generally tubular configuration so as to extend around an exterior of the propeller of the marine motor. The hydrofoil wing is affixed to an underside of the anti-cavitation plate of the marine motor. The hydrofoil wing has a first edge with a notch formed therein so as to receive a portion of the marine motor. A forward edge of the hydrofoil wing has inwardly curved forward edges on opposite sides of the notch. The shroud member is affixed to the hydrofoil wing such that a central axis of the shroud member extends at an angle of between 50.degree. and 20.degree. relative to the plane of the hydrofoil wing.

Abstract: A watercraft drive has a double rudder propeller driven by a driving engine via a driving shaft (1), an angular gear (3, 4) and an output transmission shaft (5). A propeller (6, 7) is arranged at each end of the output shaft. A guiding device made of guide blades (8a, 8b) is arranged between the propellers to correct aerodynamic conditions between both propellers (6, 7) and thus to reduce energy losses.

Abstract: An integrated splash and anti-cavitation plate is provided for an outboard motor. The integrated plate decreases the overall weight of the outboard motor in order to improve the motor's performance. The decreased weight also lessens the load on the mounting structure which supports the outboard motor on the watercraft transom. In addition, the distance between the plate and the rotational axis of the propulsion shaft is such that the plate can effectively prevent water splash-up into the mounting structure, even when the outboard motor is run with its propellers partially exposed.