GB2216480A

GB2216480A - Marine propeller drive system

Info

Publication number: GB2216480A
Application number: GB8903281A
Authority: GB
Inventors: Steven Charles Hahn
Original assignee: GKN Automotive Inc
Current assignee: GKN Driveline North America Inc
Priority date: 1988-03-08
Filing date: 1989-02-14
Publication date: 1989-10-11
Anticipated expiration: 2009-02-14
Also published as: GB8903281D0; JPH01269697A; FR2628386A1; DE3907494A1; CA1319051C; FR2628386B1; GB2216480B

Description

MARINE PROPELLER DUVE SYSTEM This invention relates to marine propeller

drive systems for boats and, more particularly, to a marine propeller drive, system having an articulated propeller shaft incorporating a constant velocity joint.

Over the years, three systems have become preferred for IU marine propeller drive systems. These are known as "outboard", "inboard-outdrive",and "inboard" propeller drive systems. Each of these have distinct operating features and characteristics that determine which of these is the system of choice for a particular application.

The outboard propeller drive system has a self-contained motor and drive train for the propeller which is mounted aft of the boat, onto a specially adapted mounting structure built into the transom; Tt has the advantage oF easy servicing, as the motor can be easily removed from the boat. More importantly, it has the advantage that the unit as a whole rotates when a turn is initiated. This means that the propeller thrust axis is caused to rotate into the turn, which greatly improves handling at low speeds and makes single propeller maneuvering when in reverse relatively easy. The outboard propeller drive system, however, has the disadvantage of being expensive because of mechanical complexity. Further, it is inefficient because a substantial structure is located below the water surface, resulting in viscous drag. Additionally, the point of contact of the propeller drive system with the boat is at a location on the transom high above the hull, resulting in thrust from the propeller drive system not being aligned with the hull. Finally, these outboard propeller drive systems tend to add considerable weight aft o the transom, frequently resulting in difficulty in achieving proper planing of the boat at low to moderate speeds of operation.

The inboard-outdrive propeller drive system has the motor contained in the boat itself, but the propeller drive mechanism is contained in an external outdrive unit which is aft of the transom. Generally, the external outdrive unit is secured, to the transom and articulates relative thereto, functioning much liKe the propeller drive of an outboard propeller drive system.

The inboard-outdrive propeller drive system has the advantage that commercially available engines, after marine modification, may be used, thus, substantially reducing costs. Further, becausi the external outdriye unit rotates when a turn is initiated, the propeller thrust axis rotates, as in the outboard propeller drive system, thus greatly enhancing low speed and reverse maneuvering capability.

There are numerous examples of inboard-outdrive propeller drive systems. U.S. Patent No. 3,136,287 to North is exemplary of an inboard outdrive, and also generally exemplary of the compl ex mechanical linkage frequently associated with inboard- outdrive propeller drive systems. North attaches his external outdrive unit to a tiltable intermediate member which is in turn attached to the transom. A universal joint allows tilting and steering of the external outdrive unit. Many other inboard- 2U' outdrive propeller drive systems have been developed, including U.S. Patent No. 3,368,516 to MacDonald et al which utilizes a constant velocity joint; U.S. Patent No. 3,368,517 to MacDonald et al which utilizes a Cardan universal joint; U.S. Patent No.

3,38Z,838 to Bergstedt which utilizes an inclined drive shaft and bevel gear; and U.S. Patent No. 3,826,219 to Nossiter which.utili zes a drive transmission that permits articulation without use of universal joints. U.S. Patent No. 3,487,804 to Kiekhaefer is of interest to show an improved inboard-outdrive propeller drive system incorporating an air stream'at the propeller to reduce viscous drag. The inboard-outdrive retains many of the advantages of the outboard, while retaining essentially all of its disadvantages, as enumerated above.

The inboard propeller drive system has the motor and transmission entirely contained within the boat. Most commonly, a propeller shaft exits from the hull forward of the transom and angles downwardly to a point near the transom. In these systems, the propeller shaft is not articulated, and the propeller is retained in a fixed relationship with respect to the hull. Because of the fixed position of the propeller, it is very difficult, if notimpossible, to steer the boat when operating at low speeds or in reverse. To solve this problem, it is well known in the art to provide two spaced apart propeller shafts. By operating the proDeller shafts at different angular velocities, it is possible for the skipper to achieve a torque couple that will steer the boat. While a second propeller shaft can aid low speed and reverse maneuverability, it is expensive and is not generally as maneuverable as the inboard and inboard-outdrive propeller drive systems. Inboard propeller drive systems have the advantage of utilizing conventional motors and transmissions which are adapted for marine use, thus reducing the expense of these com- 16 - ponents. Further, the torque axis generated by the propeller is generally in line with and directed onto the hull, thereby greatly aiding the performance characteristics of the boat.

One form of the present invention relates to inboard propeller drive systems that incorporate propeller shafts which exit the boat through the transom. A particular case in point is an inboard propeller drive system for surface effect propellers. Surface effect propellers are utilized in high performance boat applications, where it has been found that the propeller efficiency is highest when it operates partially out of the water.

Accordingly, in these surface effect propeller drive systems, the propeller shaft is located on the transom near the waterline. An example of a surface effect propeller drive system is U.S. Patent No. 3,933,13 to Adams et al. Adams et al disclose a marine propeller drive system having an articulatable propeller shaft incor- porating a double-Cardan universal joint. a propeller cover, and a thrust bearing box for the propeller shaft. The propeller is able to articulate in the vertical as well as the horizontal directions. Propeller thrust is transferred to the transom at the attachment location of the thrust bearing box. A second example of a surface effect propeller drive system is U.S. Patent No. 4,565,532 to Connor. Connor discloses an articulatable propeller 11 shaft incorporating a double-Cardan universal joint, a gimbal ring mounting for the propeller shaft and a vertically stacked gear box. The gear box requires extensive structure aft of the transom. Propeller thrust is transferred to the transom where the gear box attaches to the transom. Both the Adams et al and Connor marine propeller drive systems involve complicated structures, requiring disposition of the propeller far aft of the transom. Furtne, the mounting and drive structures of the Adams et al and Connor marine propeller drive systems require mounting to the lu transom, thereby precluding operation in situations involving conventional inboard marine propeller systems where the shaft is mounted under the hull. Additionally, the Adams et al and Connor marine propeller drive systems utilize double-Cardan universal joints which, although sometimes referred to incorrectly as "constant velocity universal joints",are not actually constant velocity universal joints as shaft vibration is present caused by speed variations in the joint. Finally, the Adams et al and Connor marine propeller drive systems deliver propeller thrust generally onto the transom, an undesirable feature, since for best 2U performance and maneuverability, propeller thrust should be delivered to the boat at the hull, in line with the propeller shaft.

Hencei there remains in the art the need to provide an inboard propeller drive system which has the capability of providing the maneuverability of outboard and inboard-outdrive pro- peller drive systems, while substantially retaining the external structural simplicity and hull directed propeller thrust delivery of conventional inboard propeller drive s ystems. There further remains in the prior art the need to provide the aforesaid maneuverability and hull directed propeller thrust delivery utilizing a true constant velocity universal joint, as exemplified by the Rzeppa type.

The present invention provides marine propeller drive systems as defined in claims 1, 9 and 16.

Thus the drive system can incorporate a true constant velocity universal joint for articulating the propeller shaft assembly, wherein the constant velocity universal joint transmits torque to the proppeller, while none of the propeller thrust is transmitted therethrough. Further, it is possible to direct propeller thrust in line with a propeller. shaft so that propeller thrust may be delivered to the boat at the hull. A preferred system will now be described.

An inner propeller shaft connects at one end to the engine transmission at a location within the boat. The inner propeller shaft connects at the other end to the inner race of a constant velocity universal joint. An outer propeller shaft connects at one end to the outer race of the constant velocity universal joint, the propeller being connected to the other end thereof.

Thrust produced by rotation of the propeller is directed by the outer propeller shaft to thrust bearings. The thrust bearings transfer the propeller thrust to an outer thrust housing which generally surrounds, but does not contact, the outer race of the constant velocity universal joint. The propeller thrust is then directed to an inner thrust housing having an annulus in which the inner propeller shaft is located.

Steering is accomplished by rotation of a steering shaft having connection to the outer thrust housing. When the outer thrust housing is rotated, the thrust bearing causes the outer propeller shaft to rotate as well.

Thus, with this structure, the propeller shaft is articulated by incorporation of a true constant velocity universal joint; further, propeller thrust is routed around the joint and directed axially in line with the inner propeller shaft. Because of these structural features, the propeller thrust is transferred directly to the hull of the boat, rather than the transom.

6 Further, the system may be mounted either through the transom or at the hull, the latter being the practice in conventional inboard propeller drive systems.

It is possible to achieve a compact, uncomplicated, vibration-free marine propeller drive system having an articulated propeller shaft. the marine propeller drive system being mountable either via the trans-om or via the hull.

These and other advantages, features, and benefits of the present invention will become apparent from the following description, by way of example. with reference to the accompanying drawings. in which:

Figure 1 is a part-sectional side view of a marine propeller drive system in operation. mounted via a boat transom; Figure 2 is a fragmentary part-sectional side view of the constant velocity universal joint of the drive system; Figure 3 is a detailed fragmentary part-sectional side view of the drive system; Figure 4 is a part-sectional side view of the thrust bearing of the drive system; Figure 5 is an end view of the drive system in operation as in Figure 1; and Figure 6 is a part-sectional side view of a marine propeller drive system in operation. mounted via a boat hull.

Referring now to the drawings, Figure 1 shows a marine 1 propeller drive system 10 according to the present invention mounted through a transom 12 of a boat 14. The marine propeller drive system 10 has an articulated propeller shaft including a fixed position inner propeller shaft 16, a constant velocity uni- versal joint 18,and a pivotable outer propeller shaft 20. Thrust from a propeller 22 is transferred to an outer thrust housing 24, an inner thrust housing 26 and, finally, to the boat hull 28.

Referring now to Figures 1 through 5, the structure of the marine propeller drive system may be understood. The inner propeller shaft 16 is connected at one end to a conventional marine power plant including an engine and transmission (not shown) which are located within the boat 14. As may bebest seen from Figure 2, the inner propeller shaft connects at its other end to an inner race member 30 of the constant velocity universal joint 18.

The constant velocity universal joint 18 is preferably, but not requisitely, of the type represented by U.S. Patent Nos. 1,665,280 and 2, 046,584 both issued to Alfred Rzeppa. ThIs type of universal joint has the superior advantage that the speed at' 2U rotation of the shaft connected with the inner race member is the same as the shaft connected with the outer race member, regardless of the relative angular position between the inner and outer race members, within a predetermined range of relative angular pas itions. Referring to Figure 2,. the constant velocity universal joint 18 transmits torque through a plurality of spherical ball members 32 (one being shown in Figure 2). These spherical ball members revolve in sets of opposing axial grooves 34 and 36 formed, respectively, on a partially spherical surface 38 of the inner race member 30 and a partially spherical surface 40 of the outer race member 42. IM11 guide means, in the form of a cage 44, are positioned to capture and guide the spherical ball members through a homokinetic plane of rotation wherein the centers of the spherical ball members bisect the articulation angle between the spherical surfaces of the inner and outer race members, resulting in a constant velocity of rotary motion without vibratinn. The ball cage normally consists of outer and inner partially spherical surfaces 46 and 48, which are guided, respectively, on the afore said partially spherical surfaces of the outer and inner race mem bers, with radial clearance therebetween in order to ensure the presence of adequate lubrication.

The inner propeller shaft 16 connects with the inner race member 30 by interaction of straight splines 50 and 52, respectively, on the inner propeller shaft and on the inner race member 30. The outer propeller shaft 20 is connected integrally with the outer race member 42. An end 61 of the outer propeller IU shaft has the propeller 22 removably attached thereto in a conven- tional manner. Specifically a conventional propeller has axially located splines within a mounting bore for being received on the propeller shaft. Splines 54 on an outer surface 56 of the outer propeller shaft 20 and a bolt 58 (shown in Figures 1 and 5) which I is threadingly received in an axially blind bore 60 in the end 61 of the outer propeller shaft removably attach the propeller to the outer propeller shaft 20.

When the propeller rotates ' it will generate thrust which will be delivered to the outer propeller shaft 20. The 20- constant velocity universal joint 18 cannot accept, through its internal components, axial thrust of this magnitude. Accordingly, the present invention includes a structure which routes propeller thrust around the constant velocity universal joint, the constant velocity universal joint interacting with the outer propeller shaft 20 only to deliver rotational torque thereto.

Referring now to Figures 1, 3,and 4, the structure to accomplish routing of the axial thrust is shown. A thrust ring 62 is welded to the outer propeller shaft 20. The thrust ring has a shoulder 64 which abuts a thrust bearing 66. The thrust bearing is preferably conventional a type "SS" two row bearing assembly, shown particularly in Figure 4. The type "SS" two row 6earing assembly utilizes a high volume type TS bearing 68 with a snap ring cup spacer 70 in a rolled ring cup spacer 72. The snap ring cup spacer 70 has a snap ring 74 which inter-fits within a recess 76 of the outer thrust housing 24. Thus, axial thrust from the propeller 22 is transmitte d along the outer propeller shaft 20 to the thrust ring 62 to the type IISSII two row bearing assembly and, finally, to the outer thrust housing via the snap ring.

A steering shaft 78 is connected in a conventional manner to a conventional steering control (not shown). Preferably, the conventional steering control is of the type including a hydraulic cylinder and a tie rod which interfaces with the steering shaft, the hydraulic cylinder being actuated by movement of a steering wheel on the boat,'the steering shaft, in kind, rotating with rotation of the steering wheel. The steering shaft inserts into a steering shaft hub 80 of the Inner thrust housing 26, and rotates on a sleeve 82 within the steering shaft hub. The steering shaft 78 protrudes through the inner thrust housing into a steering shaft aperture 84 in the outer thrust housing. The steering shaft 78 has a bore 86 and the outer thrust housing 24 also has a bore 88 into which a pin 90 is inserted. The pin 90 cooperates with the bores 86 and 88 to cause the outer thrust housing 24 to rotate with rotation of the steering shaft 78.

Oppositely located on the inner thrust housing 26 from the steering shaft hub 80, is a skag plate hub 92. A skag plate shaft 94 is rotatably mounted in the skag plate hub, the skag plate shaft rotating on a sleeve 96 within the skag plate hub.

The skag plate shaft protrudes through the inner thrust housing in the manner hereinabove described for the steering shaft 78. Specificallyi a bore 98 in the skag plate shaft 94 and a bore 100 in the outer thrust housing accommodate a pin 102 inserted thereinto. Accordingly, when the outer thrust housing rotates in response to rotation of the steering shaft, the skag plate shaft similarly rotates. A mount 104 is included on the skag plate shaft 94 for mounting a skag plate 106 (shown in Fiqure 2) thereto. The skag plate aids accomplishing directional movement of the propeller in response to steering shaft rotation, in a manner well known in the art. 1.

Referring again to Figure 1, inner thrust housing 26 has an annulus 108 into which the inner propeller shaft is located. The inner thrust housing enters the boat at the transom and then terminates in a connection member 110 which connects in a well- known manner with a retaining structure 112 that is preferably anchored to the hull 28 of the boat. Accordingly, propeller thrust is.delivered to the boat structure in a manner which is cnaracteristic of a marine propeller drive system having only a.

f prGDeller shaf t transfer of Ithrust to the boat, vet the constant 1.

ly universal joint and tne inner propeller shaft have been veloci spared suojection to the propeller thrust.

It is preferred tnat the interior of the inner and outer -o ensure full and proper thrust housing ze lubricant filled 16 luDrication of the constant velocity universal joint. This may include connection in a conventional manner to an oil pump system well Knoin in.he art.

Boots and seals are provided to ensure hydraulic integrity of tne marine prooeller drive system 10 according to the L.

present invention. A steering boot 114, constructed of a Pleated, resi I i ent materi a I, i s secured by a f i rst snap ring 116 to one end 118 of the outer thrust housing 24, a recess 120 being Provided for interfilt'hLing oil a nib 122 of #the steering boot. The steering 'her end in the manner previously recited boot is secured at its ot to a boot ring 124, the boot ring being attached t-o the base of both the steering shaft hub 80 and the skaq plate hub 92, soecifically, a snap ring 1161, recess 1201 and nib 122' are used therefor. An optional transom Doot 126 is provided to seal the entry location of the inner thrust housing 26 into the transom 12. A snap ring 128 is used to secure the transom boot to the inner thrust housing; a nib and cooperating recesses hereinabove described could be used as well if desired. The transom boot may be sealed with respect to the transom using a compression fit or a clip ring 130 which is itself secured to the transom. An outer housing lip seal 132 is located between the outer thrust housinq 24 and the thrust ring 62. A steering shaft seal 134 is provided at the end 136 of the steering shaft hub 80; likewise, a skag plate shaft seal 138 is provided at the end 140 of the skag plate hub 92.

Figure 5 shows the marine propeller drive system 10 according to the Present invention seen from the rear of the boat 14. In this figure, the propeller has been directed off angle from the axis of the inner propeller shaft during a turning maneuver.

The operational configuration 142 as shown in Figures 1 and 5 is a surface effect propeller inboard marine propeller drive system. As indicated hereinabove, a surface effect propeller 22 is used in high performance applications in which a portion of the propeller is out of the water. Accordingly, a propeller cover 144 is provided which may or may not be mounted so as to follow directional changes in the outer propeller shaft. The operational configuration 146 shown in Figure 6 is for a conventionally located propeller inboard marine propeller drive system. A conventional propeller 221 is structured for operation entirely submerged. It will be seen that the standard propeTler shaft mounting structure used in conventional inboard marine propeller drive systems may be replaced by steering shaft hub 801. Thus, in this operational configuration 146, the marine propeller drive system according to the present invention is mounted to the hull 281, the transom 121 being free of any attachments thereto. The components hereinabove described for the operational configuration 142 shown in Figures I through 5 apply equally for the operational configuration 146 shown in Figure 6.

It is preferred that there be a slight angular variation between the axis of rotation 149 of the inner propeller shaft in relation to the axis of rotation 150 of the outer propeller shaft, in order that the constant velocity universal joint be continuously in movement, thereby stirring lubricants therein con6.ained.

In operation, torque is delivered from a conventional marine power plant to the inner propeller shaft. The torque then transfers through the constant velocity universal joint through the outer propeller shaft and, finally, to the propeller. Thrust from the propeller is directed from the outer propeller shaft to a thrust ring, to a thrust bearing, to the outer thrust housing, to the inner thrust housing and, finally, to the boat hull in coaxial alignment with the inner propeller shaft. Propeller thrust applied to the outer propeller shaft, which communicates to the outer race member 42 of the constant velocity universal joint 18, is not transferred to the inner race member 30 and the inner pro- peller shaft 16 because the inner propeller shaft is axially slidable via the splines 50 and 52 while propeller thrust is directed to the outer and inner thrust housing. Steering is accomplished by rotating the steering shaft through a conventional steering linkage connected to a steering wheel, as Is well known in the steering shaft rotates, the outer thrust hous ing rotates, causing the outer propeller shaft to rotate similarly. Further, the skag plate shaft is caused to rotate similarly as well. The skag plate offers hydraulic resistance during the aforesald rotation of the steering shaft, thereby aiding steering of the boat.

It will be appreciated, therefore, that the marine drive propeller system according to the present invention will provide for maneuvering at low forward speeds and in reverse speeds with only one propeller drive being required, the propeller drive delivering thrust directly to the hull of the boat.

To those skilled in the art to which this Invention appertains, the abovedescribed preferred embodiment may be sub- ject to chance or modification. Such changes or modifications can be carried out without departing from the scope of the invention, which is intended to be limited only by the scope of the appended claims.

t 13

Claims

Claims:-

1. A marine propeller drive system for a boat having a marine power plant and a propeller for producing thrust, comprising: an inner propeller shaft having a first end connectable to the marine power plant; a constant velocity universal joint having a first end which is articulatable with respect to a second end thereof and which is connected with a second end of the inner propeller shaft; an outer propeller shaft having a first end, which is connected with the second end of the constant velocity universal joint, and a second end'structured to removably receive the propeller; means for transmitting torque from the marine power plant to the propeller; means for transmitting thrust from the propeller to the boat, the thrust being transmitted so as to bypass at least the first end of the constant velocity universal joint and the inner propeller shaft; and means for causing articulation of the outer propeller shaft with respect to the inner propeller shaft.

2. The marine propeller drive system of claim 1, the propeller having an axially located splined mounting bore, wherein the means for transmitting torque compr_ises: first splines on the first end of the constant velocity joint; second splines on the second end of the inner propeller shaft, the first and second splines gearingly meshing to permit the inner propeller shaft to move axially with respect to the first end of the constant velocity joint; and 14 third splines on the second end of the outer propeller shaft for gearingly meshing with the splined mounting bore of the propeller.

3. The marine propeller drive system of claim 1 or 2. wherein the means for transmitting thrust comprises:

a thrust bearing connected with the outer propeller shaft; an outer thrust housing connected with the thrust bearing; and an inner thrust housing connected with the outer housing, the inner thrust housing having an annulus into which the inner propeller shaft is at least in part located.

4. The marine propeller drive system of claim 3. wherein the means for causing articulation comprises:

steering shaft hub on the inner thrust housing; steering shaft rotatably mounted on the steering shaft hub, the steering shaft having a bore adjacent one end thereof; the outer thrust housing having a steering shaft aperture for receiving the said one end of the steering shaft and having a bore aligned with the said bore in the steering shaft when the steering shaft is received in the steering shaft aperture; and a pin insertable in the said bores for transmitting rotational movement of the steering shaft to the outer thrust housing.

5. The marine propeller drive system of claim 3 or 4, the boat having a transom, wherein the inner thrust housing is adapted to be mounted to the boat via the transom, the thrust being delivered by the inner thrust housing to the hull and further being delivered to the boat in axial alignment with the inner propeller shaft.

6. The marine propeller drive system of claim 3 or 4. wherein the inner thrust housing is adapted to be mounted to the boat via the hull, the thrust being delivered by the inner thrust housing to the hull and further being delivered to the boat in axial alignment with the inner propeller shaft.

7. The marine propeller drive system of any of claims 3 to 6, further comprising a skag plate rotatably mounted to the inner thrust housing, the skag plate being rotatable with the outer thrust housing.

8. The marine propeller drive system of any preceding claim, wherein the constant velocity joint has an inner race member connected with the second end of the inner propeller shaft and an outer race member connected with the first end of the outer propeller shaft.

9. A marine propeller drive system for a boat having a marine power plant and a propeller for producing thrust, comprising: an inner propeller shaft having a first end connectable to the marine power plant; a constant velocity universal joint having an inner race member and an outer race member, one of which is connected with a second end of the inner propeller shaft; an outer propeller shaft having a first end, which is connected with the other race member, and a second end structured to removably receive the propeller; a thrust bearing connected with the outer propeller shaft; an outer thrust housing connected with the thrust bearing; an inner thrust housing connected with the outer thrust housing, the inner thrust housing having an annulus into which the inner propeller shaft is at least in part located; 16 means for transmiting torque from the marine power plant to the propeller: and means for causing articulation of the outer propeller shaft with respect to the inner propeller shaft.

10. The marine propeller drive system of claim 9, the propeller having an axially located splined mounting bore, wherein the means for transmitting torque comprises:

first splines on the said one race member; second splines on the second end of the inner propeller shaft, the first and second splines gearingly meshing to permit the inner propeller shaft to move axially with respect to the said one race member; and third splines on the second end of the outer propeller shaft for gearingly meshing with the splined mounting bore of the propeller.

11. The marine propeller drive system of claim 11 or 12, wherein the means for causing articulation comprises:

steering shaft hub on the inner thrust housing; steering shaft rotatably mounted to the steering shaft hub, the steering shaft having a bore adjacent one end thereof; the outer thrust housing having a steering shaft aperture for receiving the said one end of the ste.ering shaft and having a bore aligned with the bo re of the steering shaft when the steering shaft is received in the steering shaft aperture; and a pin insertable in the said bores for transmitting rotational movement of the steering shaft to the outer thrust housing.

12. The marine propeller drive system of any of claims 9 to 11, the boat having a transom, wherein the inner 17 thrust housing is adapted to be mounted to the boat via the transom, the thrust being delivered by the inner, thrust housing to the hull and further being delivered to the boat in axial alignment with the inner propeller shaft.

13. The marine propeller drive system of any of claims 9 to 11, wherein the inner thrust housing is adapted to be mounted to the boat via the hull, the thrust being delivered by the inner thrust housing to the hull and further being delivered to the boat in axial alignment with the inner propeller shaft.

14. The marine propeller drive system of any of claims 9 to 13, further comprising a skag plate rotatably mounted to the inner thrust housing, the skag plate being rotatable with the outer thrust housing.

15. The marine propeller drive system of any of claims 9 to 14, wherein the inner race member is connected with the second end of the inner propeller shaft and the outer race member is connected with the first end of the outer propeller shaft.

16. A marine propeller drive system for a boat having a marine power plant and a propeller for producing thrust, comprising: an inner propeller shaft having a first end connectable to the marine power plant; a universal joint having a first end which is articulatable with respect to a second end thereof and which is connected with a second end of the inner drive shaft; an outer propeller shaft having a first end, which is connected with the second end of the universal joint, and a second end structured to removably receive the propeller; 18 means for transmitting torque from the marine power plant to the propeller; means for transmitting thrust from the propeller to the boat, the thrust being transmitted so as to bypass at least the first end of the universal joint and the inner propeller shaft, the thrust being delivered to the hull and being delivered to the boat in axial alignment with the inner propeller shaft: and means for causing articulation of the outer propeller shaft with respect to the inner propeller shaft.

17.The marine propeller shaft drive system of claim 16, the propeller having an axially located splined mounting bore, wherein the means for transmitting torque comprises: first splines on the first end of the universal joint; second splines on the second end of the inner propeller shaft, the first and second splines gearingly meshing and permitting the inner propeller shaft to move axially with respect to the first end of the universal joint; and third splines on the second end of the outer propeller shaft for gearingly meshing with the splined mounting bore of the propeller.

18. The marine propeller drive system of claim 16 or 17, wherein the means for transmitting thrust comprises: a thrust bearing connected with the outer propeller shaft; an outer thrust housing connected with the thrust bearing; and an inner thrust housing connected with the outer thrust housing, the thrust inner housing having an annulus into which the inner propeller shaft is at least 19 in part located.

19. The marine propeller drive system of claim 18, wherein the means for causing articulation comprises: a steering shaft hub on the inner thrust housing; a steering shaft rotatably mounted on the steering shaft hub, the steering shaft having a bore adjacent one end, the outer thrust housing having a steering shaft aperture for receiving the said one end of the steering shaft, the outer thrust housing further having a bore aligned with the said bore in the steering shaft when the steering shaft is received in the steering shaft aperture.; and a pin insertable in the bores for transmitting rotational movement of the steering shaft to said outer thrust housing.

20. The marine propeller drive system of claim 18 or 19. the boat having a transom, wherein the inner propeller shaft and the inner thrust housing are adapted to be mounted to the boat via the transom.

21.The marine propeller drive system of claim 18 or 19, wherein the inner propeller shaft and the inner housing are adapted to be mounted to the boat via the hull.

22. The marine propeller drive system of any of claims 18 to 21, further comprising a skag plate rotatably mounted on the inner thrust housing. the skag plate being'rotatable with the inner thrust housing.

23. A marine propeller drive system substantially as described with reference to, and as shown in, Figures 1 to 5 or Figure 6 of the accompanying drawings.

24. A boat having a marine power plant within the boat and a marine propeller drive system according to any 1, preceding claim.

-i Published 1989 atThefttentOfftee, State House. 66!71 High Holborn, London WClR 4TP. PurLhereoplesii2aybeobtFUnedfrom The Patentoffice. Sales Branch, St Maz7 Cray, Orpington, Rent BR5 3RD. Printed by Multiplex techniques ltd, St Mary Crikv, Kent, Con- 1187