Abstract: An outboard motor includes a first exhaust passage connected to an exhaust port and extending downward from the exhaust port through a support frame on a lateral side of a cylinder head. A first case accommodates an engine. A second case accommodates a propeller shaft. A third case is between the first case and the second case in a vertical direction. An exhaust pipe is between the first case and the second case in the vertical direction. The exhaust pipe is connected to the first exhaust passage. At least a portion of the exhaust pipe is outside the third case as seen in a side view of the outboard motor. An exterior cover is between the first case and the second case in the vertical direction. The exterior cover covers the exhaust pipe.

Abstract: An outboard motor includes an outboard-motor main-body, an anti-ventilation plate, and a foreign-matter collection apparatus. The anti-ventilation plate is provided on the outboard-motor main-body. The foreign-matter collection apparatus is provided above the anti-ventilation plate and outside the outboard-motor main-body and located at a height such that a water intake is submerged under water when a ship to which the outboard-motor main-body has been attached is in a pre-planing state.

Abstract: A marine propulsion unit includes a propeller that rotates around a rotation axis of a propeller shaft, a case in which the propeller shaft is disposed, and a skeg that extends downward from the case. The skeg includes a reinforcer with a mechanical strength greater than that of a base material of the skeg.

Abstract: An outboard motor includes a gear housing configured to rotatably house a propeller shaft that transmits a rotative power output from an engine to a propeller device. The gear housing includes a torpedo shape portion and a strut portion. The torpedo shape portion has a shape tapered toward a front side, and a shape biased upward toward the front side. The strut portion is disposed on an upper side of the torpedo shape portion. An outer peripheral surface of the torpedo shape portion is smoothly coupled to an outer peripheral surface of the strut portion via first to third curved surfaces. The first to third curved surfaces are each a curved surface inclined rearward and downward, a curved surface parallel to a front-rear direction, or a curved surface constituted of a part inclined rearward and downward and a part parallel to the front-rear direction.

Abstract: The present invention provides improvements to a fluid bearing for a journal, one being a polymer bearing pad with an outer surface, at least one recess for receiving lubricating fluid from a base of the fluid bearing and distributing the lubricating fluid to the outer surface and a mount for securely mounting the polymer bearing pad to the base. Other improvements include a fluid bearing with the polymer bearing pad, steps for making the polymer bearing pad and fluid bearing, a fluid bearing with a polymer bearing pad having a chamfer and a multidirectional fluid bearing.

Abstract: A multi-stage watertight chamber is provided in this invention. The multi-stage watertight chamber comprises a first rotary seal, a second rotary seal, a first housing, a second housing, and an integrated shaft. The first and second rotary seals withstand external pressure to make sure watertight status is achieved when the integrated shaft rotates. The first housing forms a first watertight chamber. The integrated shaft protrudes through the first housing via the first rotary seal. The second housing is placed outside and adjacent to the first housing and forms a second watertight chamber. The first watertight chamber contains devices that must be isolated from liquid outside the first and second housings. The second watertight chamber is used to store water seeped through the second rotary seal and avoid causing damage directly to components and apparatus inside the first watertight chamber.

Abstract: A propeller drive assembly, for steering and driving a ship (1), comprises a drive motor (2) and a transmission housing (4) secured to a ship hull and a control housing (7) secured to an exterior surface of the hull. The control housing (7) comprises a propeller (8) supported on a driven shaft (6) and the control housing (7) is pivotably coupled, via a steering shaft (10), to the transmission housing (4) for steering the ship (1). A transmission output shaft (5) is connected with the driven shaft (6) and a lubricant circuit of the transmission housing (4) is separate from a lubricant circuit of the control housing (7). At least one sealing element is provided, in a region of a shaft passage of the transmission output shaft (5) and in a region of a shaft passage of the steering shaft (10), for mutually sealing the transmission housing lubricant circuit and the control housing lubricant circuit.

Abstract: An outboard electric motor kit that includes an electric motor assembly with a unitized propeller hub, a transom mount, a rechargeable electric battery, and an optional recharger. The assembly includes an electric motor unit located in an upper housing. A lower tube stem is attached and that extends downward from the upper housing to a lower housing. Formed on the lower housing is a receiving cavity with a rearward facing propeller hub opening. A drive shaft coupled to the motor unit extends downward inside the lower tube stem and mounted to a gear support block located in the receiving cavity. Mounted on the end of the drive shaft is a main gear. Mounted on the gear support block is a fixed axle that extends coaxially aligned through the propeller hub opening. Extended through the opening and coaxially mounted over the fixed axle is a removable propeller hub assembly.

Abstract: A marine drive comprises a gear case housing a vertical driveshaft that rotates a generally horizontal propulsor shaft in a forward direction upon operational engagement with a forwardly rotatable gear and a rearward direction upon operational engagement with a rearwardly rotatable gear. A lubricant exclusion cover is disposed between the forwardly and rearwardly rotatable gears so as to limit churning of lubricant by at least one of the forwardly and rearwardly rotatable gears.

Abstract: In a electric corrosion preventing structure of a marine vessel propelling machine, a cylinder is integrally formed in a cylinder block, an electric connection portion is provided in a portion in which a rod guide is fixed to the cylinder, an electric connection portion is provided in a portion in which a piston is fixed to a rod in an inner portion of the cylinder, and the piston fixed to the rod strikes against the rod guide in an electrically connected state, at a maximum extension when the rod protrudes out of the cylinder.

Abstract: An outboard engine includes a buoyant member (20). The buoyant member has concavities (20L, 20R; 120L, 120R) formed in at least one side thereof. A plurality of outboard engines is mounted in parallel on the stem, and the concavities prevent interference with the other adjacent outboard engines when any of the outboard engines are tilted up.

Abstract: A support for the upper drive shaft of a marine stern drive unit. The support has an axial body installable in the axial bore of the upper case. Retainers on the body are engageable with the upper case to secure the support in place. One or both retainers are axially adjustable relative to the body. Adjustment may be achieved at threaded sections on the body which matingly engage threaded sections on the retainer.

Abstract: An outboard motor lower-unit lock has a key, a locking pin assembly and a shaft. To install the lock, a user drills a shaft hole the same diameter as the shaft through both sides of a housing unit below an access hole of the housing unit. The shaft is inserted in the shaft hole, and oriented so that a threaded hole in the center of the shaft can receive a threaded pin section of the locking pin. The locking pin receives the key. The key is tightened. Finally, the user removes the key allowing the locking pin to rotate around and below the shaft, thereby obstructing a bolt securing the lower-unit to the housing unit, and preventing the unauthorized removal of the lower-unit.

Abstract: An outboard motor S has: a first drive shaft 31 interlocked with an internal combustion engine, a second drive shaft 32 interlocked with the first drive gear 31, an output gear mechanism 50 driven by the second drive shaft 32, a propeller shaft 17, and a gear case 13 holding the output gear mechanism 50 and the propeller shaft 17 and having a normally submerged gearing holding portion 21. The second drive shaft 32 is disposed rearward of the first drive shaft 31 with respect to a longitudinal direction. The gearing holding portion 21 has a tapered part 21a extending forward from a position corresponding to the second drive shaft 32 and having a front end 21c. The tapered part 21a is tapered toward the front. The disposition of the second drive shaft 32 rearward of the first drive shaft 31 enables forming the gear case 13 in a small size and reduces underwater resistance to the gear case 13.

Abstract: An outboard motor includes a case extending generally vertically and supported on a hull. An engine is supported at an upper end of the case. A propeller is supported by a lower end of the case. A drive shaft is supported within the case for rotation about a generally vertical axis. The driveshaft has an upper end operatively connected to the engine and a lower end operatively connected to the propeller. An upper portion of the case includes an elongate extruded portion having substantially the same cross-sectional shape along its length.

Abstract: A marine propulsion device is provided with a breakaway skeg having first and second attachment points. The first and second attachment points are configured to result in the second attachment points disengaging from a gear case or housing structure prior to the first attachment point. The attachment points can comprise open or closed slots and, when an open slot is used for the first attachment point, it can be provided with a first edge along which a first pin can exert a force along a preselected angle in response to an impact force on the skeg. The arrangement of attachment points allows a reaction force at the second pin to be predetermined in a way that assures the detachment of the skeg from the housing structure prior to the detachment of the housing structure from another structure, such as the boat hull, or transom.

Abstract: A drive shaft supporting structure for a small boat is provided which permits simplification of a hull and for which manufacturing productivity is increased. The drive shaft supporting structure includes a shaft-supporting member for rotatably supporting a drive shaft inside of a hull, and an elongate cylindrical sleeve. The cylindrical sleeve is arranged between the shaft-supporting member and a hull opening which permits penetration of the drive shaft through the hull. The drive shaft supporting structure is configured in such a manner that a front end portion of the cylindrical sleeve is connected to the shaft-supporting member and a rear end portion of the cylindrical sleeve is connected to the hull opening.

Abstract: A support for the upper drive shaft of a marine stern drive unit. The support has an axial body installable in the axial bore of the upper case. Retainers on the body are engageable with the upper case to secure the support in place. One or both retainers are axially adjustable relative to the body. Adjustment may be achieved at threaded sections on the body which matingly engage threaded sections on the retainer.

Abstract: In an outboard drive or an inboard-outboard drive, power generated by a single engine is transmitted in left and right directions from a main drive shaft, thereby finally causing left and right propellers to be rotated, the left and right propellers being arranged about the main drive shaft so as to be spaced apart from the main drive shaft at approximately equal distances from the main drive shaft and facing a travel direction of a marine vessel, the outboard drive or inboard-outboard drive being provided with left and right shift cam assemblies for causing rotation situations of the propellers to be controlled dependently from each other, the rotation situations including normal rotation, reverse rotation and non-rotation situations of the propellers.

Abstract: A marine propulsion system drive unit is provided with a polymer layer to protect its outer surface from abrasion and corrosion. The polymer layer is injection molded around the outer surface of a metallic gear case structure or drive shaft housing to provide a coat which is approximately 3 millimeters thick and which will resist scratching and corrosion. The polymer layer can be a glass filled polymer or a carbon filled polymer. An adhesion promoter can be used to enhance the bonding and intimate contact between the inner surface of the polymer layer and the outer surface of the metallic gear case structure or drive shaft housing.

Abstract: A propeller assembly is provided for mounting on a propeller shaft of a watercraft. The propeller assembly includes a housing structure having a plurality of blades projecting radially therefrom. A bushing assembly translates rotatational movement of the propeller shaft to the housing structure. The bushing assembly includes a spindle having an inner surface that meshes with the outer surface of a propeller shaft and a resilient bushing molded over the spindle. A plurality of spaced, longitudinally extending keys extend along the outer surface of the spindle. In the event that the propeller blades become fixed during operation of the watercraft, the keys fragment from the outer surface of spindle so as to disengage the spindle from the housing structure. In such manner, damage to the engine and to the drive system of the marine vehicle may be avoided.

Abstract: An outboard engine comprises a power source inside a power source compartment. The power source room is formed by an upper cover and an undercover. A buoyant body is disposed outside the power source compartment, and has a lower surface wall in a position that is lower than the undercover. The buoyant body is provided separately from the upper cover.

Abstract: An arrangement and method for parallel alignment of propeller shafts in a first and a second underwater housing arranged on the hull of a vessel, which underwater housings are arranged to rotate around an axis of rotation which is angled in relation to the propeller shafts arranged in each underwater housing, which arrangement includes a servo motor arranged for each underwater housing, which servo motor is arranged to rotate said underwater housing. A position sensor arranged for each servo motor, which position sensor is arranged to detect an angular position of the underwater housing. A control unit in which a reference angular position of the underwater housing is arranged to be stored during a calibration of the position of the underwater housing; and a calibrator of the position of the underwater housings by storing output signals from the position sensors in the control unit during a parallel alignment of propeller shafts in two underwater housings arranged on the hull of a vessel.

Abstract: A marine propulsion device is made of first and second portions which are removably attachable to each other. The second portion is the leading edge portion of the nose cone and the drive shaft housing. It can also comprise a portion of the skeg. The second portion is configured to crush more easily in response to an impact force than the first portion. This can be accomplished by making the second portion from a different material than the first portion, which can be aluminum, or by providing one or more crush boxes within the structure of the second portion to cause it to yield more quickly to an impact force and thus protect the first portion which is the more critical structure of the marine device.

Abstract: A retaining ring assembly and method of assembly is disclosed. A gearcase includes a propeller shaft housing that is retained in the gearcase. The propeller shaft housing is secured against rotational, radial, and axial movement by a retainer. The retainer has a general circular shape and includes a first ring and a second ring. Both rings include a plurality of collinear threaded holes. Threaded fasteners secure the first ring to the second ring via the threaded holes in each respective ring. The first ring has a tapered surface that engages with a tapered surface of the propeller shaft housing. The second ring has an outer diameter that engages with an annular groove on an inner surface of the gearcase. As the threaded fasteners of the retainer are tightened, the tapered face of the first ring is forced against the tapered face of the propeller shaft housing while the second ring is retained in position by the annular groove of the gearcase.

Abstract: In a drive shaft support structure for a marine propulsion machine, a gear case is provided with a vertical drive shaft receiving bore, and a drive shaft driven by an internal combustion engine is supported for rotation in the drive shaft receiving bore. A gear case is provided with a gear chamber connected to the lower end of the drive shaft receiving bore. A bevel gear mechanism for transmitting power from the drive shaft to a propeller shaft is disposed in the gear chamber. The drive shaft is supported for rotation in a bearing. The bearing is fitted in the drive shaft receiving bore and is held fixedly in place with a bearing-fastening member screwed in an internal threaded part of the drive shaft receiving bore. A covering member provided with a central hole through which the drive shaft is passed is attached to the gear case so as to close the open upper end of the drive shaft receiving bore in a liquid-tight fashion.

Abstract: The present invention relates to an installation arrangement for a ship's propulsion unit comprising a modular motor unit (1) located outside the ship's body. Said motor unit comprises a motor (25) and a propeller (5) and it is intended to be connected to a structure (3) connected to the ship. At the end (7) opposite to said propeller (5) said motor unit (1) comprises fitting means arranged for fitting said motor unit (1) longitudinally to corresponding fitting means (6, 12) arranged at said structure (3) connected to the ship. The present invention also relates to a method in this context, according to which method said motor unit (1) is fitted, by the use of a longitudinal displacement in the direction of the motor's shaft (26), to a fitting piece comprising a connector plug means (12) which co-operates with corresponding means at said motor unit for supplying electrical power to the motor.

Abstract: A process for forming an improved anodizing film on the surface of an aluminum alloy material. The film is impregnated with an amorphous substance which fills pores formed in the film during its growth. If the film has a flaw reaching the aluminum alloy material, the amorphous substance and aluminum form a layer of passivity which restrains the corrosion of the aluminum alloy material.

Abstract: The present invention, in one aspect, relates to a propeller shaft housing for being secured in the gear case bore and configured for being securely engaged to the gear case bore by threaded screws that pass through bosses in the housing and into threaded holes in the gear case. More specifically, in an exemplary embodiment, the propeller shaft housing includes at least two bosses having compound angle holes therethrough, and at least two threaded holes in the gear case are arranged to align with one of the respective holes through the bosses. Respective screws extend through the holes in the bosses of the propeller shaft housing and into threaded engagement with the threaded holes in the gear case. In the exemplary embodiment, one of the threaded holes in the gear case is adjacent a skeg, and one of the threaded holes is adjacent a strut.

Abstract: A support for the vertical drive shaft of a marine stem drive unit. The support is a generally tubular member of high quality steel or steel alloy which is threaded at its lower end. The upper end carries an external flange. The upper end defines an internal taper which receives a bearing assembly. The flange is secured in the unit by a fastener and the threaded lower end is secured by a retainer such as a spanner nut. The drive shaft extends within the support substantially increasing the horsepower capacity of the unit by several times.

Abstract: The present invention, in one aspect, relates to a propeller shaft housing for being secured in the gear case bore and configured for being securely engaged to the gear case bore by threaded screws that pass through bosses in the housing and into threaded holes in the gear case. More specifically, in an exemplary embodiment, the propeller shaft housing includes at least two bosses having compound angle holes therethrough, and at least two threaded holes in the gear case are arranged to align with one of the respective holes through the bosses. Respective screws extend through the holes in the bosses of the propeller shaft housing and into threaded engagement with the threaded holes in the gear case. In the exemplary embodiment, one of the threaded holes in the gear case is adjacent a skeg, and one of the threaded holes is adjacent a strut.

Abstract: An outboard motor includes a power head, driveshaft housing and lower unit, and employs a cooling system to cool the driveshaft housing. Portions of the driveshaft housing experience substantial heat transfer from the exhaust gases that pass through the driveshaft housing. The driveshaft housing cooling system cools the heated portions of the driveshaft housing. The cooling system includes delivery pipes adapted to deliver water to the outer surface of each side of the driveshaft housing. The water is distributed to the housing outer surface in a manner to establish a substantially even flow across the surface so that heat is dissipated from the housing in order to prevent the housing from reaching very high temperatures.

Abstract: A propulsion system for a boat has a powerhead or a motor with an exhaust port for exhaust gases. The exhaust gases are exhausted through the propeller hub via an exhaust housing. The exhaust housing is a walled enclosure having an inlet, an internal volume in flow communication with the inlet, and an outlet in flow communication with the internal volume. The exhaust housing further includes hollow structures for dividing a portion of the internal volume into a plurality of flow channels which extend in side-by-side relationship. The transverse dimensions of each flow channel is substantially less than the transverse dimensions of the walled enclosure. The result is that standing waves are shifted to a higher frequency range. The hollow dividing structures have internal volumes which communicate with space external to the exhaust housing via openings in the walled enclosure, which allow the admission of a cooling medium.

Abstract: A housing for an outdrive is installed with a replaceable tower support for a ball bearing race through which the drive shaft rotates. When the bearing race becomes worn, rather than replacing the entire housing and installing a new bearing race, only the tower support and worn bearing race is removed and replaced, which represents a considerable cost saving.

Abstract: A boat drive mechanism is constructed of an engine mounted in the boat; a propeller; a drive shaft having a front end connected to the engine and a rear end extending through the exterior of the transom; a propeller shaft having a rear end connected to the propeller and a front end, with the propeller shaft being moveable between a lowered position and a raised position; and a universal joint connecting the drive shaft rear end to the propeller shaft front end and spaced from the rear of the transom, the universal joint being the sole thrust connection between the drive shaft and the propeller shaft. A propeller tube surrounds at least a part of the propeller shaft. The propeller tube and shaft are raised and lowered by a first hydraulic cylinder pivotally connected to the propeller tube and the transom above the drive shaft.

Abstract: A driveshaft housing for an outboard motor includes an improved construction. The outboard motor comprises a power head containing an engine, the driveshaft housing depending from the power head and containing a driveshaft, and a lower unit depending from the driveshaft housing and supporting a propulsion device. The engine includes an exhaust system having an exhaust conduit at least in part extending through the driveshaft housing. The driveshaft housing has a rib extending from one lateral side wall portion to another lateral wall portion between the driveshaft and the exhaust conduit. The stiffening rib strengthen the rigidity of the lateral side walls of the driveshaft housing, and thereby inhibits inward and outward movement of the lateral side walls, particularly in a region where the walls define a portion of an expansion chamber of the exhaust system within the driveshaft housing.

Abstract: A protective cover and method for protecting a boat propeller shaft and gears within a lower gear housing of a boat includes a cone-shaped casing having an inner surface, an outer surface, a top, and an open bottom. The inner and outer surfaces have an edge in common in which two notches are formed and extend along the inner and outer surfaces. The notches are spaced 180° apart from each other and are aligned with and placed around the skeg and upper frame of the lower gear housing of the boat so that the propeller shaft and gears are covered. The casing is retained on the lower gear housing by an elastic band.

Abstract: A marine propulsion device is provided with a water inlet system that comprises at least a plurality of frontal inlet openings at the tapered forward end of a gearcase portion of a housing structure. The water inlet system can be provided for an outboard motor or a stern drive unit. Additional water flow can be provided through side inlet formed in the housing structure of the marine propulsion device where both the frontal inlet openings and side inlet openings are connected with fluid communication with the water pump mounted within the housing structure.

Abstract: A wedge for preventing relative side to side motion between the propshaft housing and the gear case of an outboard engine is described. The wedge is configured to be located between the propshaft housing and the gear case bore inner diameter surface so that the wedge forces one side of the propshaft housing into contact with the bore surface. The wedge fills, or bridges, the clearance gap between the propshaft housing and the gear case bore surface at the location of the wedge.

Abstract: Hub assembly for the journalling of an impeller (4) or drive shaft end (3) in the pump housing (2) of a water jet propulsion unit for propulsion of a vessel. The hub assembly forms a separate, integrated assembly (6) which as a single unit can be assembled and dismounted from the stem without requiring the pump housing, impeller or drive shaft to be removed from the vessel. The hub assembly is joined together by means of a tightening nut (15), screwed onto a sleeve (9), with an inwardly positioned bearing plate (16) axially holding the sleeve in a bearing housing (8) while concurrently clamping the bearings (10, 11) between said bearing plate and a radially extended flange (17), arranged in the front end of the sleeve, so that the bearing housing, the bearings and the sleeve form a separate, integrated unit.

Abstract: A flange portion formed on an inner periphery of a flywheel is facet-fitted to an end of a crankshaft. A spline piece is facet-fitted to an inner peripheral surface of the flywheel. The flange portion of the flywheel and a flange portion of the spline piece are commonly fastened to the end of the crankshaft by bolts. An upper end of a driving shaft is spline-fitted at a point into a driving shaft coupled portion of the spline piece which is accommodated in an internal hole in the crankshaft. Thus, in coaxially coupling the flywheel and the driving shaft to the end of the crankshaft, it is possible to make such a coupled area compact and to reduce vibration by an accurate centering thereof.

Abstract: An outboard motor incorporating a mounting assembly for resiliently connecting the steering shaft to the driveshaft housing. The mounting assembly also includes locating an attachment bracket on the driveshaft housing juxtaposed to a box shaped section of the internal cavity of the driveshaft housing.

Abstract: A lower unit for an outboard drive has an elongated length in order to present a streamline shape while providing sufficient width to house a transmission for a counter-rotational propeller system with a forwardly-oriented clutch element. One of the clutch elements of the transmission lies in front of the transmission gears to increase the flow area through an exhaust discharge path behind the transmission. In order to accommodate this transmission structure, the lower unit has an increased with at a point forward of the associated drive shaft. The lower unit also has an increased length as measured from the drive shaft forward in order to present a streamline shape within the water. The elongated length of the lower unit also improves the directional and rolling stability of the outboard drive.

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.

Abstract: An improved water pickup arrangement for a marine propulsion device for picking up cooling water for the propelling, water-cooled internal combustion engine. The lower unit has a bullet-shaped portion and the water inlet openings are formed at the forward and upper ends of this portion.

Abstract: A number of embodiments of four-cycle internal combustion engines having belt-driven overhead cam shafts. The power head of the outboard motor includes a protective cowling that has an atmospheric air inlet and the air drawn through this atmospheric air inlet is directed over a timing belt that drives the cam shaft from the engine crankshaft for its cooling. The air flow is controlled either by utilization of fans, baffles and/or utilizing the flow of air caused by the induction system.

Abstract: Propulsion unit for marine vessels with a gear or bearing housing (6) in which a propeller shaft (7) with a surface-breaking propeller (8) is carried. In a horizontal plane the propeller shaft forms an angle (.alpha.) to a guide fin (9) so as to create a resultant force (R) of the pressure force (P) of the propeller and the side force (S), with the resultant force being aligned with the longitudinal direction (C.sub.L) when the vessel is travelling straight ahead.

Abstract: A nose cone attachment for an outboard motor propeller gearcase has a molded polymer housing shaped to fit over the front and sides of an outboard propeller gearcase and has an aerodynamic nosepiece shape on the front thereof with a plurality of water inlets thereon. The molded polymer housing has open water channels or plenums thereinside which form wide passageways with the gearcase housing sides when the nose cone attachment is attached over the gearcase housing. The open water channels are positioned to fit over the gearcase water inlets. The housing is adhesively attached but may also have a plurality of screw openings formed in the side thereof and positioned for attaching screws therethrough to attach the nose cone to a gearcase outboard motor prop.

Abstract: A nautical propulsion performance enhancer for a propeller of a marine propeller type propulsion system, comprising a facility for twisting and directing a flow of water into the propeller, in such a manner that swirling water will hit the propeller in a direction opposite to rotation of the propeller. A structure is for mounting the twisting and directing facility to the marine propeller type propulsion system adjacent the propeller, in order to overcome unwanted effects of cavitation and porpoising.

Abstract: A marine drive (10) has two counter-rotating surface operating propellers (12 and 14). The lower horizontal torpedo portion (188) of the housing (20) has an upper zone (276) with outer surface profiles (11T-17T) along horizontal cross-sections defining wedges with sharp leading tips (11LT-17LT) forming a sharp leading edge (278) for slicing through the water, the sharp leading tips (11LT-17LT) defining the sharp leading edge (278) defining a first line extending downwardly and rearwardly at a first angle (280) relative to vertical. The torpedo portion (188) has a lower zone (270) with outer surface profiles (1B-10B) along horizontal cross-sections defining wedges with sharp leading tips (1LT-10LT) defining a second line (272) extending downwardly and rearwardly at a second angle (274) relative to vertical.