US3842789A

US3842789A - Hydraulic trim/tilt system for outboard propulsion units

Info

Publication number: US3842789A
Application number: US00317062A
Authority: US
Inventors: K Bergstedt
Original assignee: Volvo Penta AB
Current assignee: Volvo Penta AB
Priority date: 1971-12-21
Filing date: 1972-12-20
Publication date: 1974-10-22
Anticipated expiration: 1991-10-22
Also published as: JPS5933756Y2; GB1369530A; IT974176B; SE350939B; JPS5598700U; AU5004972A; FR2170501A5; CA960917A; JPS4869287A; DE2262459A1; US3799104A; CA965650A

Abstract

A hydraulic system for trimming and tilting outboard drives for boats. The system comprises a pump adapted to deliver fluid pressure to a double acting cylinder-piston assembly, which is connected to the tiltable outboard drive unit and to a stationary part of the boat. A valve selects between two modes of operation of the cylinder. In one mode the chambers of the cylinder are interconnected to provide rapid tilt operation. In the other mode, one chamber is connected to the pump and the other is connected to the fluid sump to provide relatively less rapid trimming with greater force.

Description

United States Patent 4 191 Bergstedt 7 i5 1 HYDRAULIC TRIM/TILT SYSTEM FOR OUTBOARD PROPULSION UNITS [75] Inventor: Karl Abdon Bergstedt, Goteborg,

Sweden [73] Assignee: AB Volvo Penta, Goteborg, Sweden [22] Filed: Dec. 20, 1972 [2i] Appl. No.: 317,062

[30] Foreign Application Priority Data Dec.2l, 1971 Sweden 16407/71 52 us. Cl; 115/41 HT 511 nt. Cl B63h 5/ 2 [5'8] FieldofSearch ..'.....115/41 R, 41 HT, 34R,

[56 O i 4 References Cited i UNITED STATES PATENTS 2,451,706 10/1948 Aimes ..9l/437 3,008,445 11/1961 Frank .......l15/4 l HT [451 Oct. 22,1974- 3,654,889 4/1972 Bergstedt..,.... ll5/4l HT Primary ExaminerTrygvevM-. Blix Assistant Examiner-Charles E. Frankfort Attorney, Agent, or Firm-George H. Baldwin; Arthur G. Yeager 57 ABSTRACT A hydraulic system fortrimming andv tiltingoutboard drives for boats. The system comprises a pump adapted-to deliver fluid pressure to a double acting cylinder-piston assembly, which is connected to the tiltable outboard drive unit and ma stationary part of the boatl' A valve selects between two modes of opera:

tior'i of the cylinder. intone mode thechambers of the cylinder are interconnected to provide rapid tilt operation. In the other mode, one chamber is connected-to the pump and the other is connected-to thefluidsump to provide relatively less rapid trimming with greater force. i e v 8 Claims, 8 Drawing Figures,

HYDRAULIC TRIM/TILT SYSTEM FOR OUTBOARD PROPULSION UNITS Applicant claims priority based on Swedish application No. 16407/1971 filed Dec. 20, 1971.

BACKGROUND OF THE INVENTION In tilting and trimming outboard drives, two main requirements are to be met. In one case, the tilt movement, when the boat lies still and when no propeller thrust acts on the drive, a wide range of tilting is to be performed in a short time. Under this condition, only a relatively small force is needed. In the second case, the trimming movement, when the boat is driven and the drive is subjected to the propeller thrust, a relatively greater force is needed to achieve the trimming movement. On the other hand the trim angle is small and a low speed of the trimming movement is desirable to permit accurate setting of the trim angle.

It is known, for example from US. Pat. No. 3,548,777 Bergstedt, to fulfill the above named requirements by utilizing one hydraulic cylinder with a relatively small piston area for tilting and a second cylinder with a relatively large piston area for trimming. By this arrangement it is possible to achieve both the quick tilting movement and the slow trimming move ment with one pump with constant capacity.

It is, of course, preferred for economy, simplicity and space considerations to use one, rather than two cylinders for trimming and tilting.

It is an object of the present invention to provide a hydraulic system with which it is possible to achieve the above named trimming and tilting functions by using only one cylinder. This is accomplished by a valve unit in the hydraulic system which is adjustable between a first position, in which the chamber at the piston rod end of the cylinder is connected to the chamber at the piston end of the cylinder, and a second position, in which the chamber at the piston rod end of the cylinder is connected to the sump tank.

In the first position of the valve unit, in which it provides a short circuit between the two chambers of the cylinder, the fluid pressure delivered by the pump to the cylinder will act on the difference between the piston areas of the two chambers of the cylinder, i.e., on the cross-sectional area of the piston rod. Since this area is much smaller than the total piston area exposed to the chamber at the piston end of the cylinder, the fluid will cause a fast movement of the piston and little force, which is desired during tilting.

It is preferred that the cylinder-piston assembly is arranged, as in said US. Pat. No. 3,548,777, so that an outward movement of the piston rod causes an upward tilting of the drive unit.

In the second position of the valve unit the chamber at the piston rod end of the cylinder is drained by a connection to a sump tank. When fluid pressure is then dethe first and the second position. In this embodiment, the manually adjustable valve member is preferably coordinated to a known locking valve, which is connected to the reverse gear of the drive and adapted to lock the connection between the piston rod side of the cylinder and the tank when shifting from forward to reverse drive.

Such shifting between trim and tilt is achieved, as hereinafter seen, without using any additional control units which should complicate the maneuvring of the boat.

The hydraulic system according to the invention will be fully understood from the following description which refers to the accompanying drawings.

FIG. 1 is a side view of an inboard-outboard drive unit for a boat embodying the invention;

FIG. 2 is a schematic view of a previous known hydraulic trim/tilt system with two cylinders;

livered to the piston area, it causes a slow motion of the FIG. 3 is a schematic view of a second embodiment of the invention with a manually adjustable valve unit;

FIGS. 4a, 4b, 4c and 4d are schematic views of the different positions of the manually adjustable valve unit; and

FIG. 5 is a schematic side view of the adjusting mechanism for the valve unit in FIGS. 4 a-d.

This invention contemplates an outboard drive unit for a boat, such as the inboard-outboard unit shown in FIG. 1 as comprising an outboard leg 60 mounted for tilting on a pivot 61 to the boat transom 62. The leg is arranged for steering, for example, as shown in US. Pat. No. 3,605,677 Bergstedt, and is provided with a cylinder 63 rockably connected to a fixed portion 64 of the boat or drive unit and with an extensible piston rod 36 pivotally connected to the leg, whereby extension of the rod causes rearward trimming or tilting movement ofthe leg about pivot 61. A control cable or

rod linkage

56, 58 leads from a housing 65 which may form an integral part of the cylinder and in which control valves of the system are contained. A pump and fluid pump schematically shown at P is connected by means of fluid conduits schematically represented at 66 to supply pressure fluid to and receive return fluid from the control system. A forward, neutral and reverse gear transmission of the unit is controlled by lever 67 linked to lever 56.

The known hydraulic system showed in FIG. 2 comprises a reversible pump 1 which can deliver fluid in both directions, and it is therefore connected to the sump tank 6 over two lines 2 and 3 with back pressure valves 4 and 5. The pump is also connected to the sump tank via lines 7 and 8 comprising safety relief valves 9 and 10. The lines 2 and 3, of which one acts as a suction line and the other as a pressure line depending on the pump direction of the pump 1, connect the pump to two regulating

valve units

11 and 12, of which the first one 11 communicates, via the

lines

13 and 14, with the chamber 16 at the piston end of a double acting tilt cylinder 17 and also with a single acting trim cylinder 19 in order to regulate the fluid flow to and from these cylinders. The other regulating valve unit 12 communicates, via the line 15, with the chamber 20 at the piston rod end of the double acting cylinder 17. Both

valve units

11 and 12 also communicate with the sump tank via respective return lines 21 and 22.

Units

11 and 12 comprise respective piston means 25 and 26, which are influenced by the pressure in lines 3 and 2 and which are spring biased by

respective compression springs

23 and 24 against the pressure in the respective lines. The piston means 25 controls the communication between sump return line 21 and

lines

13 and 14 depending on the pressure in line 3, while piston means 26 controls the communication between sump return line 22 and line depending on the pressure in line 2.

The hydraulic system further comprises a lock valve 27, which is manually adjustable and is interposed in the line 15 which communicates with the chamber in cylinder 17. The system also comprises a safety relief valve 29 in a short circuit line 28 connecting between

lines

12 and 15.

Another safety relief valve is disposed in a channel in the piston 32, said

channel connecting chambers

16 and 20 of the double acting cylinder to each other.

Finally, the system also comprises a line 33, which via a relief valve 48 connects line 13 to the sump tank.

The described system suffers of very little, actually neglectable, leakage and keeps the

pistons

32 and 34 of the cylinders 17 and 19 in their adjusted positions. The hydraulic cylinders are adapted to act between a stationary part of the boat and the tiltable part of the drive unit in such a way that an outward movement of the

respective piston rods

35 and 36 causes an upward swinging movement of the drive. This arrangement, being well known in the art, is therefore not further shown in the drawings.

When the angular position of the drive unit is to be adjusted, for upward or downward tilting or trimming, the pump is actuated and connected in the desired direction until the desired position of the drive unit is achieved.

When the drive unit is to be tilted from drive position when the boat is lying still or is not being driven forward, the function of the system is as follows:

The pump is actuated and connected in a direction which makes the line 3 constitute a suction line and the line 2 a pressure line. The pressure in line 2 opens a spring biased back pressure ball valve 37 in the regulating valve unit 11, whereupon the fluid under pressure is delivered to chambers 16 and 18 in the cylinders 17 and 19 via

lines

13 and 14.

Simultaneously, the pressure in line 2 causes the piston 26 in the regulating valve unit 12 to move to the right as seen in FIG. 2 and thus to force open a back pressure valve 38 in the valve unit 12, whereupon chamber 20 in the cylinder 17 communicates with the sump tank 6 via the line 15 and the return line 22. The trimming cylinder has a relatively short stroke. As the piston 32 of the cylinder 17 has a smaller area than the piston 34 of cylinder 19 and as the same pressure prevails in the cylinder chambers 16 and 18, a fast outward movement of the piston rod 35, and thus a fast tilting of the drive, is achieved after the piston 34 has reached its limit. As seen in U.S. Pat. No. 3,548,777, the rod 36 is so arranged that the outboard leg swings away therefrom beyond the trim range.

For downward tilting of the drive the pump is actuated in the opposite direction, so that line 3 constitutes a pressure line and line 2 a suction line. It will be apparent that the direction of rotation of the pump may be reversed to provide pressure to line 3 and to draw fluid from line 2 or that merely the input and output connections to the pump may be reversed to provide this result without reversing the actual direction of rotation of the pump itself. Via a spring biased back pressure valve 39 in the regulating valve unit 12 fluid is delivered to chamber 20 in the cylinder 17. Simultaneously, the pressure in line 3 causes piston 25 in the valve unit 11 to open a spring biased back pressure valve in the valve unit 11, whereupon the cylinder chambers 16 and 18 communicate with the tank 6 via the line 13, the back pressure valve 40 and the return line 21. In this case an inward movement of the piston 32 and finally of both

pistons

32 and 34 and a downward movement of the drive are achieved.

When the boat is propelled, whereby the

piston rods

35 and 36 are exposed to the force caused by the propeller thrust which tends to press the pistons inwardly, the cylinder 17, due to its small piston area, is not able to produce an outwardly directed force which is enough to overcome the propeller force and accomplish a short movement of the drive for trimming. At trimming, whereby the fluid flow corresponds to the above described one for tilting, the short movement of the drive is instead accomplished primarily by the cylinder 19 with the piston 34 which has a larger piston area, assisted to some extent by the lesser force of piston 32.

It shall be mentioned in this connection that the cylinder 19 is preferable positioned so that a relatively long moment arm is obtained, which is made possible by the fact that only a relatively short swinging motion is needed for trimming compared with tilting. The cylinder 17, however, is positioned so that a relatively short moment arm is obtained, in order to get a fast and wide swinging movement.

Of the

other valves

27, 29 and 30 which are comprised in the hydraulic system, the valve 27 works as a lock valve which is manually adjustable together with the gear mechanism of the drive in order to block the drainage from the cylinder chamber 20. In this way it is ensured that the drive will not be tilted by the rearwardly directed propeller force during reverse drive. The valve 29 is a safety release valve which permits drainage of the chamber 20 if the drive is exposed to an extreme rearwardly directed force, for example upon impact with a submerged or floating object. Valve 30 has the same function when the lock valve 27 is in its locking position.

The hydraulic system according to the invention will hereafter be described with reference to FIGS. 3, 4a, 4b, 4c, 4d, and 5 in which the components corresponding to those in FIG. 2 have been given the same numbers as in FIG. 2. The system showed in FIG. 3 connects at

fluid lines

13, 15 and 33 to the system as shown in FIG. 2. The difference between the system according to this invention as shown in FIG. 3 and the prior art system of FIG. 2 lies, as will be seen, in the omission of cylinder 19, in the substitution of valve 50 for valve 27, and in the provision of short circuit line 52. Furthermore, since in the FIG. 2 system, the cylinder 17 performs the tilting function and the function of preventing tilting movement of the outboard leg during operation in reverse gear, whereas cylinder 63 according to the invention performs these functions as well as the function of trimming the leg during forward driving of the boat, the cylinder 63 should be of larger dimensions, for a drive unit of the same power, than are required for the cylinder 17. In other respects, cylinder 63 may be identical to cylinder 17 as above described, being provided with a throughpiston safety valve 30 for the purposes hereinabove explained.

In accord with the system of FIG. 2, line 13 is pressurized when the pump is actuated to trim or tilt the outboard leg, while a sump return connection is opened to line 15. When the pump is actuated in the reverse direction (or with reversed connections), line 15 is pressurized and line 13 is opened to a sump return line. When the pump is not actuated,

lines

13 and 15 are blocked off although, as described, the

safety valves

48, 29 and 30 are provided to prevent excessive build-up of destructive pressures therein.

According to the invention, the manually actuated valve 50 controls or provides not only the reverse lock function (ascribed to valve 27 of the system of FIG. 2) but also control and selection of the trimming and tilting operations.

The valve 50 comprises a rotatably movable valve member 51, which is connected or coupled to the reverse gear control mechanism of the drive over a lost motion mechanism (FIG. 5) so that shifting of the gears of the drive unit between forward, reverse and neutral also causes an adjustment of the valve member 51. The lost motion" mechanism is in the shown embodiment constituted by a control lever 56 with slots 55 in which pins 57 on the valve member 51 mesh. The slots are dimensioned so that a 30 lost motion of the control lever is provided before the member 51 is engaged. The control lever is connected to the reverse gear control mechanism via a push-pull rod 58 or the like.

By using a lost motion mechanism two positions of the valve member 51 are achieved in the neutral position of the drive gear and the control lever 56, namely: a first neutral position is achieved by shifting gears from forward drive to neutral, and a second neutral position is achieved by shifting gears from reverse drive to neutral. The different positions of the valve member 51 are shown in FIGS. 4a 4d. In the position shown in FIG. 4a the chamber 20 of cylinder 63 communicates with the sump tank 6 via achannel 53 in the valve member 51 and via line 15. The drive gear control is in position for forward drive. The system is now adjusted for trimming. Upon actuation of pump 1 in one direction, the outboard leg is slowly and forceably trimmed aft, or upon such actuation in the opposite direction, it is slowly trimmed forwardly. In FIG. 4b there is shown said first neutral position which is obtained by a 60 clockwise adjustment of the control lever 56 from the position in which the drive gears are engaged for forward drive into the position in which the gears are in neutral. This position of lever 56 is that shown in solid lines in FIG. 5. The lost motion between the lever and the valve member 51 is 30. The valve member is thus adjusted 30 but is still maintaining communciation between the chamber 20 and the sump tank and the system, consequently, is still in position for trimming as shown in FIG. 4b. Upon a further 60 clockwise adjustment of said lever to position the gears for reverse drive, the valve member 51 is adjusted 60 and blocks the drainage from chamber 20 as FIG. 40 shows. This corresponds to the earlier described locking position in which the drive is held down without being influenced by the backwardly directed propeller force. Upon a 60 readjustment in a counterclockwise direction of the control lever from reverse gear position to the position in which the gears are placed in neutral, a 30 adjustment of the valve member 51 is obtained to said second neutral position. In this position, as is shown in FIGS.

3, 4d and 5, the valve establishes communication between

chambers

16 and 20 of the cylinder 63 via a channel 54, the channel 53 and the short circuit line 52. This constitutes a tilting connection for the cylinder, and if, now, the pump is actuated in the tilting direction, the effective piston area is the cross sectional area of the rod 35. Finally, a further adjustment of the gear control linkage into the forward drive gear posi tion, with the accompanying 60 movement of the lever 56, returns the valve element 51 into the position shown in FIG. 4a.

In operation, boats are more frequently operated in forward gear, and only occasionally in reverse gear. So long as the gear shift linkage is shifted between forward drive and neutral, the trimming and tilting system remains in condition for trimming, with the valve element moving between its positions of FIGS. 4a and 4b. If the gears are thrown into reverse, the valve member moves into reverse lock position, FIG. 40, to prevent kicking up of the outboard leg 60. In order to tilt the leg rapidly, the linkage is shifted into reverse gear position and then returned to neutral, valve member 51 then being in its FIGS. 3, 4d and 5 position and lever 56 in the solid line position of FIG. 5. If the lever 56 is not first moved into the reverse gear position and then into neutral, tilting can be accomplished with the valve member in either of its trimming positions of FIG. 4a or FIG. 4b, though at a much slower rate than with the valve member in its FIG. 4d position.

U.S. Patents having some pertinence in connection with the present invention include No. 3,003,724 Kiekhaefer; No. 3,434,448 Woodfill; No. 3,653,270 Bergstedt; and No. 3,581,702 Moberg, in addition to No. 3,548,777 identified above.

While the invention has been described with respect to certain specific embodiments, it will be appreciated that many modifications and changes may be made by those skilled in the art without departing from the spirit of the invention. It is intended, therefore, by the appended claims to cover all such modifications and changes as fall within the true spirit and scope of the invention.

What is claimed as new and what it is desired to se-.

cure by Letters Patent of the United States is:

' 1. A hydraulic system for trimming and tilting of outboard drive unitsfor boats, comprising pump means adapted to deliver hydraulic liquid from a liquid sump to a double acting cylinder-piston assembly, said cylinder-piston assembly being arranged between said tiltable drive unit and the boat or a stationary part of the drive, characterized by a valve unit, said valve unit being adjustable between a first position and a second position and comprising means for connecting said pump means to the chamber at the piston rod end of the cylinder and to the chamber at the piston end of the cylinder when said valve unit is in said first position to tilt said drive unit and for disconnecting said chamber at said piston rod end of said cylinder from said chamber at the piston end of said cylinder and for connecting said chamber at said piston rod end of said cylinder with said sump when said valve unit is in said second,

position to trim said drive unit, and manual control means for adjusting said valve unit between its said positions.

2. In a hydraulic system for trimming and tilting an outboard drive leg for boats about a horizontal tilt axis comprising a hydraulic liquid sump, a double acting hydraulic cylinder-piston assembly including a piston rod and having a cylinder with a piston therein dividing the space in the cylinder into a first chamber at the piston end and a second chamber at the piston rod end of said cylinder, means connecting said cylinder and rod between said leg and said boat and spanning said axis, and a reversible pressure liquid pump connected to said first chamber, valve means connected to said sump and to each of said chambers adjustable between a first and a second position and comprising means for connecting said second chamber to said first chamber when in said first position to tilt said drive leg and for connecting said second chamber to said sump when in said second position to trim said drive leg, and manual control means for adjusting said valve means between its said two positions.

3. In a drive unit for a boat including a hydraulic system for trimming and tilting an outboard drive leg about a horizontal tilt axis, said system comprising a hydraulic liquid sump, a double acting hydraulic cylinderpiston assembly including a piston rod and having a cylinder with a piston therein dividing the space in the cylinder into a first chamber at the piston end and a second chamber at the piston rod end of said cylinder, means connecting said cylinder and rod between said leg and said boat and spanning said axis, and a source of pressure liquid connected to said first chamber, said unit comprising a forward, neutral and reverse gear transmission and manually movable means for shifting said gears, said system being characterized by including valve means connected to said sump and to each of said chambers adjustable between a first and a second position and comprising means for connecting said second chamber to said first chamber when in said first position to tilt said drive leg and for connecting said second chamber to said sump when in said second position to trim said drive leg, and means coupling said valve means to said manually movable means for coordinate adjustment thereof between said positions in response to gear shifting movement of said manual means.

4. The combination according to claim 3, characterized in that said valve means is further adjustable into a third position into which it is adjusted in response to movement of said manually movable means into the position to shift said gear transmission into reverse, and said valve means further comprises means for closing off said second chamber when in said third position.

5. The combination according to claim 3 wherein said means coupling said valve means to said manually movable means includes a lost motion connection.

6. The combination according to claim 3 wherein said means connecting said valve means to said manually movable means includes a lost motion connection, and wherein, upon movement of said manually movable means to shift said transmission gears from reverse into neutral, said valve means is thereby adjusted into its said first position, and, upon further movement of said manually movable means to shift said transmission gears from neutral into forward gear, said valve means is adjusted thereby into its said second position, said lost motion connection being operative, upon return movement of said manually movable means from its forward gear position to shift said transmission gears into neutral, to render said connecting means inoperative to return said valve means into its said first position.

7. The combination according to claim 6, characterized in that said valve means is further adjustable into a third position into which it is adjusted in response to movement of said manually movable means into the position to shift said gear transmission into reverse, and said valve means further comprises means for closing off said second chamber when in said third position.

8. In a drive unit for a boat including a hydraulic system for trimming and tilting an outboard drive leg about a horizontal tilt axis, said system comprising a hydraulic fluid sump, a double acting hydraulic cylinderpiston assembly including a piston rod and having a cylinder with a piston therein dividing the space in the cylinder into a first chamber at the piston end and a second chamber at the piston rod end of said cylinder, means connecting said cylinder and rod between said leg and said boat and spanning said axis, and a selectively operable pressure fluid pump means connected to said first chamber, said unit comprising a forward, neutral and reverse gear transmission and manually movable gear shift means for shifting said gears between forward, neutral and reverse, said system being characterized by including valve means connected to said sump and to each of said chambers adjustable between first, second, third and fourth positions, said valve means comprising means to open hydraulic connection between said second chamber and said first chamber when in said first position, to open hydraulic connection between said second chamber and said sump in said second and third positions, and closing off hydraulic connection to said second chamber in said fourth position, means coupling said valve means to said manually movable means for adjustment thereof coordinate with movement of said manually movable means and operable to adjust said valve means into said first position in response to movement of said manually movable means to shift gears from reverse to neutral, to adjust said valve means into said second position in response to movement of said manually movable means to shift gears from neutral into forward, to adjust said valve means into said third position in'response to movement of said manually movable means to shift gears from forward to neutral, and to adjust said valve means into said fourth position in response to movement of said manually movable means to shift gears from neutral into reverse, said lost motion means being effective, upon said movement of said manually movable means to shift gears from forward into neutral, to not adjust said valve means from said third to said first position and, upon said movement to shift gears from reverse into neutral, to not adjust said valve means from said first to said third position.

Claims

1. A hydraulic system for trimming and tilting of outboard drive units for boats, comprising pump means adapted to deliver hydraulic liquid from a liquid sump to a double acting cylinderpiston assembly, said cylinder-piston assembly being arranged between said tiltable drive unit and the boat or a stationary part of the drive, characterized by a valve unit, said valve unit being adjustable between a first position and a second position and comprising means for connecting said pump means to the chamber at the piston rod end of the cylinder and to the chamber at the piston end of the cylinder when said valve unit is in said first position to tilt said drive unit and for disconnecting said chamber at said piston rod end of said cylinder from said chamber at the piston end of said cylinder and for connecting said chamber at said piston rod end of said cylinder with said sump when said valve unit is in said second position to trim said drive unit, and manual control means for adjusting said valve unit between its said positions.

3. In a drive unit for a boat including a hydraulic system for trimming and tilting an outboard drive leg about a horizontal tilt axis, said system comprising a hydraulic liquid sump, a double acting hydraulic cylinder-piston assembly including a piston rod and having a cylinder with a piston therein dividing the space in the cylinder into a first chamber at the piston end and a second chamber at the piston rod end of said cylinder, means connecting said cylinder and rod between said leg and said boat and spanning said axis, and a source of pressure liquid connected to said first chamber, said unit comprising a forward, neutral and reverse gear transmission and manually movable means for shifting said gears, said system being characterized by including valve means connected to said sump and to each of said chambers adjustable between a first and a second position and comprising means for connecting said second chamber to said first chamber when in said first position to tilt said drive leg and for connecting said second chamBer to said sump when in said second position to trim said drive leg, and means coupling said valve means to said manually movable means for coordinate adjustment thereof between said positions in response to gear shifting movement of said manual means.

8. In a drive unit for a boat including a hydraulic system for trimming and tilting an outboard drive leg about a horizontal tilt axis, said system comprising a hydraulic fluid sump, a double acting hydraulic cylinder-piston assembly including a piston rod and having a cylinder with a piston therein dividing the space in the cylinder into a first chamber at the piston end and a second chamber at the piston rod end of said cylinder, means connecting said cylinder and rod between said leg and said boat and spanning said axis, and a selectively operable pressure fluid pump means connected to said first chamber, said unit comprising a forward, neutral and reverse gear transmission and manually movable gear shift means for shifting said gears between forward, neutral and reverse, said system being characterized by including valve means connected to said sump and to each of said chambers adjustable between first, second, third and fourth positions, said valve means comprising means to open hydraulic connection between said second chamber and said first chamber when in said first position, to open hydraulic connection between said second chamber and said sump in said second and third positions, and closing off hydraulic connection to said second chamber in said fourth position, means coupling said valve means to said manually movable means for adjustment thereof coordinate with movement of said manually movable means and operable to adjust said valve means into said first position in response to movement of said manually movable means to shift gears from reverse to neutral, to adjust said valve means into said second position in response to movement of said manually movable means to shift gears from neutral into forward, to adjust said valve means into said third position in response to movement of said manually movable means to shift gears from forward to neutral, and to adjust said valve means into said fourth position in response to movement of said manually movable means to shift gears from neutral into reverse, said lost motion meanS being effective, upon said movement of said manually movable means to shift gears from forward into neutral, to not adjust said valve means from said third to said first position and, upon said movement to shift gears from reverse into neutral, to not adjust said valve means from said first to said third position.