US3765370A

US3765370A - Means for balancing the steering forces when moving in a reverse direction

Info

Publication number: US3765370A
Application number: US00065399A
Authority: US
Inventors: W Shimanckas
Original assignee: Outboard Marine Corp
Current assignee: Outboard Marine Corp
Priority date: 1969-08-19
Filing date: 1970-08-20
Publication date: 1973-10-16
Anticipated expiration: 1990-10-16

Abstract

Disclosed herein are several arrangements for balancing ''''steering torque'''' which occurs in a stern drive unit during reverse operation, which arrangements involve designing the lower unit so as to cause generation of a balancing torque in response to striking of the lower unit by the water swirling past the lower unit during such reverse operation. In one embodiment, the stern drive unit comprises a drive shaft housing rotatably supporting a drive shaft, together with means for swingably supporting the drive shaft housing from the stern of a boat for steering movement about an axis extending co-axially with the drive shaft, and a skeg extending rigidly downwardly from the drive shaft housing and located substantially wholly forwardly of the steering axis.

Description

United States Patent n91 Shimanckas Oct. 16, 1973 [75] Inventor: William J. Shimanckas, Waukegan,

Ill.

[73] Assignee: Outboard Marine Corporation,

Waukegan, Ill.

[22] Filed: Aug. 20, 1970 [21] Appl. No.: 65,399

Related US. Application Data [63] Continuation-impart of Ser. No. 851,211, Aug. 19,

1969, Pat. NO. 3,587,510.

4 1964 Cameron 115 41 R x l/l969 Becker et a] 115/41 X Primary Examiner-Milton Buchler Assistant Examiner--Carl A. Rutledge Attorney-Robert E. Clemency, John W. Michael, Gerrit D. Foster, Bayard H. Michael, Paul R. Puemer, Joseph A. Gemignani, Robert K. Gerling, Andrew 0. Riteris and Spencer B. Michael [5 7] ABSTRACT Disclosed herein are several arrangements for balancing steering torque which occurs in a stern drive unit during reverse operation, which arrangements involve designing the lower unit so as to cause generation of a balancing torque in response to striking of the lower unit by the water swirling past the lower unit during such reverse operation. In one embodiment, the stern drive unit comprises a drive shaft housing rotatably supporting a drive shaft, together with means for swingably supporting the drive shaft housing from the stern of a boat for steering movement about an axis extending co-axially with the drive shaft, and a skeg extending rigidly downwardly from the drive shaft housing and located substantially wholly forwardly of the steering axis.

13 Claims, 3 Drawing Figures MEANS FOR BALANCING TIIE STEERING FORCES WHEN MOVING IN A REVERSE DIRECTION RELATED APPLICATION This application is a continuation-in-part of my earlier application Ser. No. 851,211, filed Aug. 19, 1969 now U.S. Pat. No. 3,587,510 issued June 28, 1971 and entitled Marine Propulsion Device with Split Drive Shaft.

BACKGROUND OF INVENTION Stern drive units differ from outboard motors, at least in part, in that a stern drive unit includes a lower unit which is swingable for steering purposes independently of the driving engine. In at least some prior stern drive constructions, the steering axis was co-axial with the axis of the drive shaft in the lower unit drive shaft housing. As contrasted to outboard motors, during driving operation of a stern drive unit and, in particular, due to opposition of the water to rotation of the propeller, a so-called steering torque is developed, which steering torque tends to swing the stern drive lower unit about the steering axis. When the stern drive unit includes a reversing transmission in the lower unit, the lower unit tends to swing in the same direction about the steering axis regardless of whether the stern drive unit is operating in either forward or reverse. If a reversing transmission is located within the boat, the drive shaft in the steerable lower unit will then rotate in opposite directions depending upon the setting of the reversing transmission, thereby developing steering torque in opposite directions in accordance with the direction of operation.

In the past, trim tabs and other means, including specific gear ratios, have been employed to balance the socalled steering torque of the stern drive unit during forward operation so that the operator would not have to constantly overcome the steering torque effect. However, no provision was made in the past for balancing steering torque during reverse operations. With stern drive units of increasing horsepower, it is especially desirable to provide for balancing of the steering torque effect during reverse operation.

Examples of prior stern drive constructions can be found in my prior U.S. Pat. No. 3,183,880, issued on May 18, 1965, and in the Alexander U.S. Pat. No. 3,136,282, issued June 9, 1965, and in the Bergstedt U.S. Pat. No. 3,382,838, issued May 14, 1968.

SUMMARY OF THE INVENTION The invention provides an arrangement for balancing steering torque developed by the drive shaft housing of a stern drive unit during reverse operation. The arrangement utilizes sail areas on the lower unit and the water which twirls toward the lower unit from the propeller and which strikes such sail areas to create a balancing torque.

More specifically in the preferred embodiments of the invention, when the stern drive unit is operating in reverse with the drive shaft rotating in one rotative direction as seen from above and with the propeller shaft rotating in the opposite direction as seen from in front, the invention comprises maximizing sail areas forwardly of the steering axis and below the propeller shaft as compared to rearwardly of the steering axis and below the propeller shaft and/or maximizing sail areas below the water line and rearwardly of the steering axis and above the propeller shaft as compared to forwardly of the steering axis and above the propeller shaft so as to utilize the swirling water moving past the lower unit during reverse operation to counterbalance the steering torque.

In other embodiments of the invention, when the stern drive unit is operating in reverse with the drive shaft rotating in one rotative direction as seen from above and with the propeller shaft rotating in the same rotative direction as seen from in front, the invention comprises maximizing sail areas rearwardly of the steering axis and below the propeller shaft as compared to forwardly of the steering axis and below the propeller shaft and/or maximizing sail areas below the water line and forwardly of the steering axis and above the propeller shaft as compared to rearwardly of the steering axis and above the propeller shaft so as to utilize the swirling water moving past the lower unit during reverse operation for counterbalancing the steering torque.

Thus, in the preferred embodiments in accordance with the invention, i.e., when the drive shaft and propeller shaft are rotating in opposite rotative directions as seen respectively from above and in front, the skeg is preferably designed to be essentially wholly located forwardly of the steering axis and the drive shaft housing below the water line and above the propeller shaft can be extended rearwardly as far as possible to in crease the sail areas which are effective to counterbalance steering torque occurring during reverse operation.

In other embodiments in accordance with the invention, when the drive shaft and the propeller shaft are rotating in the same rotative direction as seen respectively from above and in front, the skeg is preferably designed to be essentially wholly located rearwardly of the steering axis and the drive shaft housing can be, as far as possible, reduced rearwardly of the propeller shaft and from below the water line to above the propeller shaft to increase the comparative sail areas which are effective to counterbalance steering torque during reverse operation.

One of the principal objects of the invention is the provision of a stern drive unit including means for balancing steering torque when the unit is operating in reverse.

Another of the principal objects of the invention is the provision of a stern drive unit which is designed to employ the swirling stream of water moving past the lower unit when in reverse operation to effectively counter the steering torque resulting from rotation of the drive shaft in the lower unit.

Another of the principal objects of the invention is the provision of a stern drive including means for balancing steering torque when operating in reverse by dimensioning components conventionally generally included in the stern drive unit construction to take advantage of the swirling stream of water which passes v the lower unit when operating in reverse.

Other objects and advantages of the invention will become known by reference to the following description and accompanying drawings.

DRAWINGS FIG. 1 is a partially broken away side elevational view of a stern drive unit embodying various of the features of the invention.

FIG. 2 is a partially broken away side elevational view of another embodiment of a stern drive unit in general accordance with the invention.

FIG. 3 is a partial elevational view of still another embodiment of a stern drive unit in general accordance with the invention.

GENERAL DESCRIPTION Shown generally in FIGS. 1 and 2 are respective stern drive units 11 and 13 which are adapted to be connected to the stern of a boat (not shown) and which conventionally includes respective lower units 17 and 19 including respective drive shaft housings 21 and 23 rotatably supporting respective drive shafts 27 and 29, together with respective means 31 and 33 for swingably supporting the drive shaft housings 21 and 23 from the stern of a boat hull (not shown) for steering movement about respective axes. While the invention is not, in its broadest sense so limited, in the disclosed construction, the respective steering axes extend substantially coaxially with the respective drive shafts 27 and 29. The stern drive units 11 and 13, shown in FIGS. 1 and 2, also include

respective skegs

37 and 39 which, in accordance with the invention, are each preferably substantially wholly located forwardly of the respective steering axes and are at least located principally forwardly of the respective steering axes.

More particularly, in the preferred stern drive unit embodiment shown in FIG. 1, the lower unit 17 is supported on a boat (not shown), as for instance, from the transom, and the drive shaft housing 21 is both tiltable about a horizontal axis 41 and steerable about an axis 42 perpendicular to the tilt axis and co-axial with the drive shaft 27.

Still more particularly, the drive shaft housing 21 includes an upper part 43 which can be tiltably supported from the boat in any suitable manner. For instance, the upper drive shaft housing part 43 can be mounted on trunnions extending from a bracket or other member fixed to the boat transom, whereby to afford vertical tilting movement of the drive shaft housing 21. The drive shaft housing 21 also includes a lower part 47 which is supported by bearings 49 within the upper part 43 for swingable steering movement about the axis 42 which is perpendicular to the tilt axis 41. A gear 50 on the upper end of the lower part 47 is provided to facilitate steering movement of the lower part 47 relative to the upper part 43. The drive shaft 27 is rotatably carried in the lower drive shaft housing 47 co-axially with the steering axis by bearings 51 and, at its upper end, is connected through a suitable drive connection including a bevel gear 55 to a prime mover (not shown). As shown in FIG. 1, when seen from above, the drive shaft 27 is rotated in the counterclockwise direction as shown by the arrow 56. At its lower end, the drive shaft 27 carries a bevel gear 57 which is in mesh with another bevel gear 59 mounted on the upper end of a power shaft 61 which is vertically supported for rotation by bearings 63 in the lower drive shaft housing part 47.

Employment of the power shaft 61 with the drive shaft 27 is particularly desirable as this construction serves to locate the reversing transmission at a more forward location in the lower 'unit and to permit location of a more or less full size skeg forwardly of the steering axis for purposes which will be explained in greater detail hereinafter.

At its lower end, the power shaft 61 extends into a gear box portion 65 on the lower drive shaft housing part 43 and is connected through a suitable reversing transmission 67 with a propeller shaft 69 which is carried by suitable bearings 71 in the gear box portion 65 and which carries a propeller 73. Extending below and integrally from the gear box portion is the skeg 37.

The reversing transmission includes, as is conventional, a bevel gear 62 at the lower end of the power shaft 61, a forward drive bevel gear 64 located forwardly of the power shaft 61, and in mesh with the bevel gear 62, and a rearward drive bevel gear 66 located rearwardly of the power shaft 61 and in mesh with the bevel gear 62. Although any suitable electrical, hydraulic or mechanical means can be employed, in the disclosed construction, a slideable dog 68 is employed to selectively connect the bevel gears 64 and 66 to the propeller shaft 69 to respectively effect forward and reverse operation. It is preferred to use the reversing transmission 67 in which the forward bevel gear 64 is located forwardly of the reverse bevel gear 66.

As a consequence of the use of the reversing transmission 67, when the stern drive unit 11 is operating in reverse, the drive shaft 27 rotates in the counterclockwise direction as seen from above, the power shaft 61 rotates in the clockwise direction as seen from above, and due to the engagement of the bevel gear 62 with the reversing bevel gear 66, the propeller shaft 69 rotates in the clockwise direction as seen from in front and as shown by the arrow 70. Thus, it will be seen that in the preferred construction, the drive shaft 27 and propeller shaft 69, when seen respectively from above and from in front, rotate in opposite rotative directions. If desired, the drive shaft 27 could be rotated in the clockwise direction as seen from above and the propeller shaft 69 could be caused to rotate in the counterclockwise direction as seen from in front by using the same reversing transmission 67.

It should be further noted that in the preferred construction shown in FIG. 1, employment of the power shaft 61 serves to permit counter-rotation of the drive shaft 21 and propeller shaft 69 as above explained while, at the same time, employing the reversing transmission 67 with the forward gear 64 located forwardly of the bevel gear 62 and with the reversing gear 66 located rearwardly of the bevel gear 62, which arrangement of the reversing transmission is preferred.

In particular accordance with the invention, means are provided for balancing the steering torque developed by rotation of the drive shaft 27 when the engine is operating. In the disclosed construction, such means comprises dimensioning the sail areas, i.e., the more or less flatside areas 81 of the drive shaft housing 21 below the water level and above the gear box portion 65 or propeller shaft 69 including the area 83 in front of the steering axis 42 and the area 85 rearwardly of the steering axis 42, as well as the flat sides of the skeg 37 below the gear box portion 65, so that the water which swirls past the drive shaft housing 21 during reverse operation acts on the

sail areas

81 and 37 so as to provide a torque or moment counter to the steering torque caused by drive shaft rotation in the drive shaft housing 21.

Thus, in accordance with the invention, the skeg 37 is substantially wholly located forwardly of the steering axis 42. In addition, if desired, the sail area 85 above the gear box portion 65 and rearwardly of the steering axis 42 can be increased as indicated by the dotted line 86 to provide additional sail area and consequent moment for balancing the steering torque in reverse operation.

In operation, the drive shaft 27 rotates in the counterclockwise direction as seen from above and as shown by the arrow 56 and the propeller shaft 69 rotates, when operating in forward drive condition, in the counterclockwise direction when seen from the front, carrying water flow rearwardly from the lower unit. As already indicated, the steering torque created by such drive shaft rotation occurring when the reversing transmission 67 is in forward can be balanced by prior known methods including proper selection of the angle between the drive shaft 27 and the propeller shaft 69 and/or trim tabs located on the lower unit rearwardly of the propeller 73.

When the transmission 67 is shifted into reverse, the propeller shaft 69 turns in the opposite or clockwise direction as seen from the front and as indicated by the arrow 70, causing a swirling stream of water to strike or impinge against the

sail areas

81 and 37. If the sail areas fore and aft of the steering axis are of equal size, there will be little or no moment or torque developed to counter the steering torque developed by drive shaft rotation within the drive shaft housing 21. However, by decreasing or eliminating the sail area of the skeg 37 below the gear box and rearwardly of the steering axis 42, i.e., essentially by terminating the skeg 37 at or forwardly of the steering axis 42, the twirling flow of water striking the skeg sail area 37 will create a torque or moment tending to oppose or balance the steering torque. In addition, by balancing as closely as possible the sail area 85 with the sail area 83, the full effect of the torque or moment created by the striking of the skeg 37 by the swirling water can be obtained. Still further, it is desirable to dimension the sail area 85 so that it is larger than the sail area 83 to produce a positive torque or moment augmenting the moment created by the skeg 37. In this regard, it is noted that the sail area 85 can be increased by extending rearwardly the rearward margin of the lower unit as shown, for instance, in dotted outline at 86.

While it is preferred that substantially all of the skeg 37 be located forwardly of the steering axis, it will, of course, be appreciated that any difference in skeg sail area caused by a larger area in front of the steering axis 42 as compared to rearwardly of the steering axis 42 will be helpful in overcoming steering torque occurring during reverse drive operation.

The stem drive unit 13 shown in FIG. 2, can be constructed generally as described in my earlier Shimanckas US. Pat. No. 3,183,880 which construction is incorporated herein by reference, except that as will be understood, the construction of the lower unit portions beneath the water line have been altered in order to take advantage of various of the features of the invention.

More specifically, the stern drive unit shown in FIG. 2 employs a reversing transmission 167 which is in mesh with a bevel gear 162 located at the lower end of the drive shaft 29 which is supported co-axially with the steering axis 142 by bearings 189 and which rotates in the counterclockwise direction when seen from above and as indicated by the arrow 156. The reversing transmission 167 includes a reverse bevel gear 166 which is in mesh with the bevel gear 162 and which is located forwardly of the drive shaft 29, together with a forward bevel gear 164 which is in mesh with the bevel gear 162 and which is located rearwardly. of the drive shaft 29. Any suitable hydraulic, electrical or mechanical means can be employed to selectively engage the forward and reverse bevel gears 164 and 166 with the propeller shaft 169. In the disclosed construction, a clutch dog 168 is carried on the propeller shaft 169 for selective engagement with the forward and reverse bevel gears 164 and 166 respectively to effect forward and reverse drive operation. Accordingly, when in reverse drive operation, the propeller shaft 169 will rotate in the clockwise direction when seen from in front as indicated by the arrow 170. In addition, the sail area above the propeller shaft 169 and rearwardly of the drive shaft 29 and/or steering axis 142 is larger as compared to the sail area 183 forwardly of the drive shaft 29 and the sail area of the skeg 39 is essentially wholly located forwardly of the drive shaft 29 or steering axis 142.

In operation, in reverse drive, the swirling stream of water produced by the propeller 173 acts on the skeg 39 and on sail area 185 rearwardly of the steering axis and above the propeller shaft 169 to produce a torque or moment tending to counterbalance the steering torque produced incident to rotation of the drive shaft 29, thereby tending to increase the ease with which an operator can effect steering movement during reverse operation.

In FIG. 3 there is fragmentarily shown another stern drive unit 213 which embodies various features of the invention and which, except as will be explained, is constructed essentially the same as the stern drive unit 13.

In this regard, the stern driveunit 213 includes a steerable lower unit 219 having a drive shaft housing 223 rotatably supporting a drive shaft 229 which is rotated in the counterclockwise direction as seen from above and as indicated by the arrow 256.

Mounted on the lower end of the drive shaft 229 is a bevel gear 262 which cooperates with a reversing transmission 267 including a forward bevel gear 264 in mesh with the bevel gear 262 and located forwardly of the drive shaft 229 and a reverse bevel gear 266 which is in mesh with the bevel gear 262 and located rearwardly of the drive shaft 229. Any suitable electrical, hydraulic or mechanical means can be employed to selectively connect the forward and

reverse bevel gears

264 and 266 to a propeller shaft 269 carrying a propeller 273. In the disclosed construction, such means comprises a slideable clutch dog 268 which can be suitably actuated. It is noted that the disclosed construction desirably locates the forward bevel gear 264 forwardly 'of the drive shaft 229.

In view of the arrangement of the reversing transmis-' sion 267, when the drive shaft 229 is rotated in the counterclockwise direction as seen from above, the propeller shaft 169 will also rotate, when the transmission is in reverse, in the counterclockwise direction as seen from in front and as indicated at 270. As a result, in order to counterbalance the steering torque created by rotation of the drive shaft 229 in the counterclockwise direction as seen from above, there is provided a skeg 239 located principally rearwardly of the steering axis 142 which is co-axial with the drive shaft 229. In addition, the lower unit in the area above the propeller shaft 269 and below the water line and in the area rearwardly of the drive shaft 229 is reduced in area and terminates as indicated at 286 so as to provide a sail area 283 forwardly of the drive shaft 229 which is larger than the area rearwardly of the drive shaft 229. As a consequence, when the drive shaft 229 and propeller shaft 269 are rotated in the same rotative direction, when respectively seen from above and in front, the water swirling past the lower unit will strike the sail area 283 and the skeg 239 to produce a torque operating counter to the steering torque developed consequent to rotation of the drive shaft and operation of the propeller shaft in the water.

It is noted that when the drive shaft and the propeller shaft are rotating in opposite rotative direction, when respectively seen from above and in front, it is preferred to increase the sail area below the water line and above the propeller shaft and to the rear of the steering axis and to increase the sail area below the propeller shaft and in front of the steering axis, while at the same 7 time, as far as possible, to decrease the sail area below the propeller shaft and rearwardly of the steering axis and below the propeller shaft and forwardly of the steering axis while maximizing sail areas below the water line and above the propeller shaft and forwardly of the steering axis and below the propeller shaft and rearwardly of the steering axis.

The principles of the invention are applicable to any marine propulsion device in which the lower unit is steerable relative to the engine. In addition, while the disclosed embodiments have all included a reversing transmission in the lower unit and a drive shaft which rotates in the same direction regardless of the direction of operation of the unit as a whole, the principles of the invention are also applicable to such stern drive units as may employ a reversing transmission between the engine and the steerable drive shaft housing such that the drive shaft rotates in opposite directions to produce opposite propulsions.

Various of the features of the invention are set forth in the following claims.

What is claimed is:

l. A stern drive unit comprising a lower unit rotatably supporting a drive shaft, means for swingably supporting said lower unit from the stern of a boat for movement about a steering axis through an arcuate range of less than 90 to either side of a centered position, a propeller shaft rotatably supported in said lower unit and driven by said drive shaft, said propeller shaft and said drive shaft rotating in opposite directions as seen respectively from in front and above when in reverse operation, and means including sail areas on said lower unit for counterbalancing steering torque occurring during reverse operation of said stern drive unit.

2. A stern drive unit in aocordance'with claim 1 wherein the sum of the sail area below the water line and above the propeller shaft and rearwardly of the steering axis and the sail area below the propeller shaft and forwardly of the steering axis is greater than the sum of the sail area below the water line and above the propeller shaft and forwardly of the steering axis and the sail area below the propeller shaft and rearwardly of the steering axis.

3. A stern drive unit in accordance with claim 2 wherein the axis ofv said drive shaft and said steering axis are co-axial.

4. A stern drive unit comprising a drive shaft housing including at the lower end thereof a gear box, a propeller shaft rotatably mounted in said gear box, a drive shaft rotatably mounted in said drive shaft housing and drivingly connected to said propeller shaft, means for swingably supporting said drive shaft housing and said connected gear box from the stern of a boat for steering movement about an axis extending co-axially with said drive shaft, and a skeg extending rigidly downwardly from said gear box and being substantially wholly located forwardly of the axis of steering movement.

5. A stern drive unit comprising a drive shaft housing including at the lower end thereof a gear box, a propeller shaft rotatably mounted in said gear box, a drive shaft rotatably mounted in said drive shaft housing and drivingly connected to said propeller shaft, means for swingably supporting said drive shaft housing and said connected gear box from the stern of a boat for steering movement about an axis extending coaxially with said drive shaft, and a skeg extending rigidly downwardly from said gear box and having a rearward edge at or forwardly of the axis of steering movement.

6. A stern drive unit in accordance with claim 5 wherein said drive shaft extends substantially at a right angle to said propeller shaft.

7. A stern drive unit in accordance with claim 5 wherein said drive shaft extends at an acute angle to said propeller shaft.

8. A stern drive unit in accordance with claim 4 wherein said drive shaft extends substantially at a right angle to said propeller shaft.

9. A stern drive unit in accordance with claim 4 wherein said drive shaft extends at an acute angle to said propeller shaft.

10. A stern drive unit comprising a drive shaft housing including at the lower end thereof a gear box, a propeller shaft rotatably mounted in said gear box and extending substantially horizontally, a drive shaft rotatably mounted in said drive shaft housing, extending substantially downwardly and rearwardly, and drivingly connected to said propeller shaft, means forswingably supporting said drive shaft housing and said connected gear box from the stern of a boat for steering movement about an axis extending co-axially with said drive shaft, a skeg extending rigidly downwardly from said gear box and being located substantially wholly forwardly of said steering axis, and a power shaft drivingly connected between said drive shaft and said propeller shaft.

11. A stern drive unit in accordance with claim 10 wherein said power shaft extends substantially at a right angle to said propeller shaft and has at the lower end thereof a first bevel gear and further including a reversing transmission including a forward drive bevel gear in mesh with said first bevel gear and located forwardly of said power shaft, a reverse drive bevel gear in mesh with said first bevel gear and located rearwardly of said drive shaft, and means for selectively connecting said forward drive and reverse drive bevel gears to said propeller shaft.

12. A stern drive unit comprising a drive shaft housing including at the lower end thereof a gear box, a propeller shaft rotatably mounted in said gear box, a drive shaft rotatably mounted in said drive shaft housing and drivingly connected to said propeller shaft, said drive shaft and said propeller shaft rotating in opposite rotative directions when respectively seen from above and in front and when said drive unit is operating in reverse, means for swingably supporting said drive shaft housing and said connected gear box from the stern of a boat for steering movement about an axis extending coaxially with said drive shaft and through an arcuate range of less than 90 to either side of a centered position, and a skeg extending rigidly downwardly from said gear box with the area of said skeg forwardly of said steering axis exceeding the area of said skeg rearwardly of said steering axis.

13. A stern drive unit comprising a drive shaft housing including at the lower end thereof a gear box, a propeller shaft rotatably mounted in said gear box, said drive shaft housing having sides defining sail areas above said propeller shaft and below the water line, a drive shaft rotatably mounted in said'drive shaft housing and drivingly connected to said propeller sahft, said drive shaft and said propeller shaft rotating in opposite directions when seen respectively from above and in front and when said drive unit is operating 'in reverse, means for swingably supporting said drive shaft housing and said connected gear box from the stern of a boat for steering movement about an axis extending coaxially with said drive shaft and through an arcuate range of less than to either side of a centered position, and a skeg extending rigidly downwardly from said gear box the sum of the sale area below the water line and above the propeller shaft and rearwardly of the,

steering axis and the area of said skeg forwardly of the steering axis being greater than the sum of the sail area below the water line and above the propeller shaft and forwardly of the steering axis and the area of said skeg rearwardly of the steering axis.

f zg o UNITED STATES PATENTEOFFICE CERTIFICATE CORRECTION Patent No. 3,765,370 Dated October 16, 1973 Inven g) William J. Shimanckas It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

clumn line 6 i f f .a*!!=l'1.mi9 3;:- :.'.hf-.;.:

Signed and sealed this 8th day of October 197 +o (SEAL) Attest:

MCCOY M. GIBSON JR. c. MARSHALL DANN Attesting Officer, Commissioner of Patents

Claims

1. A stern drive unit comprising a lower unit rotatably supporting a drive shaft, means for swingably supporting said lower unit from the stern of a boat for movement about a steering axis through an arcuate range of less than 90* to either side of a centered position, a propeller shaft rotatably supported in said lower unit and driven by said drive shaft, said propeller shaft and said drive shaft rotating in opposite directions as seen respectively from in front and above when in reverse operation, and means including sail areas on said lower unit for counterbalancing steering torque occurring during reverse operation of said stern drive unit.

2. A stern drive unit in accordance with claim 1 wherein the sum of the sail area below the water line and above the propeller shaft and rearwardly of the steering axis and the sail area below the propeller shaft and forwardly of the steering axis is greater than the sum of the sail area below the water line and above the propeller shaft and forwardly of the steering axis and the sail area below the propeller shaft and rearwardly of the steering axis.

3. A stern drive unit in accordance with claim 2 wherein the axis of said drive shaft and said steering axis are co-axial.

10. A stern drive unit comprising a drive shaft housing including at the lower end thereof a gear box, a propeller shaft rotatably mounted in said gear box and extending substantially horizontally, a drive shaft rotatably mounted iN said drive shaft housing, extending substantially downwardly and rearwardly, and drivingly connected to said propeller shaft, means for swingably supporting said drive shaft housing and said connected gear box from the stern of a boat for steering movement about an axis extending co-axially with said drive shaft, a skeg extending rigidly downwardly from said gear box and being located substantially wholly forwardly of said steering axis, and a power shaft drivingly connected between said drive shaft and said propeller shaft.

12. A stern drive unit comprising a drive shaft housing including at the lower end thereof a gear box, a propeller shaft rotatably mounted in said gear box, a drive shaft rotatably mounted in said drive shaft housing and drivingly connected to said propeller shaft, said drive shaft and said propeller shaft rotating in opposite rotative directions when respectively seen from above and in front and when said drive unit is operating in reverse, means for swingably supporting said drive shaft housing and said connected gear box from the stern of a boat for steering movement about an axis extending co-axially with said drive shaft and through an arcuate range of less than 90* to either side of a centered position, and a skeg extending rigidly downwardly from said gear box with the area of said skeg forwardly of said steering axis exceeding the area of said skeg rearwardly of said steering axis.

13. A stern drive unit comprising a drive shaft housing including at the lower end thereof a gear box, a propeller shaft rotatably mounted in said gear box, said drive shaft housing having sides defining sail areas above said propeller shaft and below the water line, a drive shaft rotatably mounted in said drive shaft housing and drivingly connected to said propeller sahft, said drive shaft and said propeller shaft rotating in opposite directions when seen respectively from above and in front and when said drive unit is operating in reverse, means for swingably supporting said drive shaft housing and said connected gear box from the stern of a boat for steering movement about an axis extending co-axially with said drive shaft and through an arcuate range of less than 90* to either side of a centered position, and a skeg extending rigidly downwardly from said gear box the sum of the sale area below the water line and above the propeller shaft and rearwardly of the steering axis and the area of said skeg forwardly of the steering axis being greater than the sum of the sail area below the water line and above the propeller shaft and forwardly of the steering axis and the area of said skeg rearwardly of the steering axis.