Self-Leveling Hydraulic Motor Driven Boat Lift

Abstract

A self-leveling hydraulic motor driven boat lift includes proximal and distal support structures disposed on respective longitudinal sides of a lift platform. A pair of proximal and distal hydraulic motors are operably mounted to the proximal and distal support structures respectively. Each hydraulic motor is operably connected to a respective winder mechanism. A lift cable assembly is operably interconnected between the winder mechanism and a respective side of the lift platform. Each hydraulic motor is reversible and communicably connected to a respective hydraulic pump, which transmits hydraulic fluid between the pump and the connected motor for operating the motor and selectively driving the connected winder mechanism and cable assembly to selectively raise and lower the lift platform. A respective restrictor valve interconnects each hydraulic pump and that pump's corresponding hydraulic motor. An angle inclination sensor detects the lateral inclination of the lift platform and transmits a corresponding signal to a controller, which selectively directs at least one restrictor valve to adjust the flow rate of hydraulic fluid transmitted between at least one pump and its respective hydraulic motor such that the lift platform is laterally leveled.

Description

FIELD OF THE INVENTION

This invention relates to a self-leveling hydraulic motor driven boat lift and, more particularly, to a boat lift having at least one pair of opposing hydraulic motors mounted on respective sides of the lift and a system for controlling the flow of hydraulic fluid to and from the opposing motors to laterally level the lift.

BACKGROUND OF THE INVENTION

Cable driven post lifts are a common variety of boat lift. Such lifts conventionally employ one or more electric motor driven winders having boat lifting cables wound thereon. These cables are typically interconnected between the winder(s) and the cradle beams or other vessel supporting platform of the lift. The electric motor drives the winder(s) to selectively raise and lower the lift cables and, in turn, the supported vessel. A system of pulleys are typically used to guide the cables and facilitate the lift operation. Cable driven boat lifts of this type are commonly mounted on pilings or other types of supportive marine structure. These lifts can also be freestanding and employ their own supportive legs, beams or other underlying framework or supportive structure.

Conventional cable driven post lifts exhibit certain limitations that hinder their use. Because one or more electric motors operate the winder, the lift cannot employ an optimally low profile, which can hinder scenic marine views and present an unattractive aesthetic appearance. Electric motors are also extremely susceptible to damage and malfunction due to the wet marine environment in which the lift is installed. Rising tides, rough waters and severe marine storms can cause havoc with and seriously impede the operation of electrical motors. As a result, such motors must be mounted well above the waterline and/or housed in water-resistant enclosures. Electric motors and connected winders must be placed at a significant height above the water. This can significantly restrict the submersibility of the lift and also increases assembly and installation costs. In freestanding lifts, an undesirably tall supportive framework and legs may be required. When the lift is mounted on existing pilings, the motor may have to be placed undesirably close to the water. Furthermore, because conventional post lifts must often be placed at a significantly elevated height, it can take an inordinately lengthy period of time to raise or lower the lift.

Hydraulic lifts have been employed in the marine industry. However, until now, such lifts have almost always featured hydraulic cylinders that are operated to selectively raise and lower the lift. Conversely, post lifts utilizing winder driven lift cables have typically been powered by electric motors. As described above, this prevents such lifts from exhibiting a desirable low profile and also subjects the lifts to an undue risk of damage and malfunction due to the proximity of the electric motor to the surrounding water and unpredictable marine conditions.

Recently, I developed a cable driven, post-style boat lift employing a hydraulic motor for operating a winder and attached lift cables to selectively raise and lower the lift platform and supported vessel. Application Ser. No. 63/528,546. The hydraulic motor avoids the damage and malfunction often experienced by conventional electrical motors installed in a wet and harsh marine environment. The hydraulic motor also allows the lift to employ an attractive, low-profile construction and permits the lift platform to be positioned in closer proximity to the waterline, which can favorably reduce the time to raise or lower the lift.

Although the foregoing lift provides a number of significant advantages, using a single motor may limit the power and capacity of the lift to effectively elevate and support heavy vessels. I have also determined that a simpler cable and pulley arrangement may be beneficial in certain boat lift applications. An effective system for stably and safely levelling a hydraulic motor driven boat lift's platform to accommodate imbalanced vessel loads is also needed.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a winder and cable driven post lift for boats and marine vessels that employs at least one pair of hydraulic motors on respective sides of the lift to provide increased lifting power and weight-supporting capacity, and to permit the use of a simpler and more reliable cable and pulley arrangement.

It is a further object of this invention to provide a self-leveling hydraulic motor driven boat lift that maintains the longitudinal sides of the lift platform and supported vessel in a balanced, level condition while the lift is being operated.

It is a further object of this invention to provide a winder and cable driven post lift for boats and marine vessels that employs one or more pairs of opposing hydraulic motors rather than conventional electric motors to reduce the risk of damage to and malfunctioning of the motor from surrounding water and other adverse conditions of a marine environment.

It is a further object of this invention to provide a hydraulic motor driven post lift featuring a low profile and greater submergibility for accommodating boats having deeper drafts and which allows the lift to operate more effectively in shallow water conditions.

It is a further object of this invention to provide a winder and cable driven post lift that greatly reduces the potential lift failure, downtime and repair costs currently associated with the use of conventional electric motor driven lifts.

It is a further object of this invention to provide a hydraulic motor post lift that raises and lowers a boat stably, quickly, reliably and in a balanced, level condition.

It is a further object of this invention to provide a hydraulic motor post lift that employs a simple and efficient cable and pulley configuration for selectively lifting and lowering the vessel supporting platform of the lift.

This invention features a self-leveling hydraulic motor driven boat lift and specifically a hydraulic motor driven post-style boat lift for use in combination with opposing proximal and distal support structures located on respective sides of a boat to selectively lift the boat out of and lower the boat into a body of water between the support structures. The lift includes at least one pair of opposing hydraulic motor assemblies that are mountable on the proximal and distal support structures respectively. A proximal hydraulic motor assembly operably interengages a proximal winder and a distal hydraulic motor assembly operably interengages a distal winder. A boat supporting platform is located between the proximal and distal support structures. The platform is suspended from the opposing proximal and distal support structures respectively by at least one proximal cable assembly and at least one distal cable assembly. Each cable assembly includes an elongate lift cable that Is connected to and windable on a respective winder. Each cable operably engages a corresponding pulley secured to the support platform. A respective hydraulic pump is communicably connected to each hydraulic motor for transmitting hydraulic fluid between the pump and connected motor to operate the motor. The pumps and connected hydraulic motors operate synchronously and are reversible for selectively driving the interengaged winders and connected cable assemblies to raise or lower the lift platform as required. In a lifting mode, the hydraulic motors drive the interengaged winders and cable assemblies raise the support platform of the lift. Alternatively, the hydraulic motors operate in a reverse direction such that the interengaged winders and cable assemblies lower the lift platform.

The hydraulic lift further includes a self-leveling system for maintaining a level height between the proximal and distal sides of the lift platform during operation of the lift. The self-leveling system may include a device for measuring the degree of lateral tilt or inclination between the opposing proximal and distal sides of the lift platform. A respective valve may be interconnected between each hydraulic pump and its communicably connected hydraulic motor. A controller responsive to signals from the incline measuring device selectively opens and closes one or both valves a selected amount to adjust the flow of hydraulic fluid between at least one pump and its connected hydraulic motor. This adjusts the speed of at least one hydraulic motor such that the motors operate to level the lift platform.

In a preferred embodiment, the incline measuring device may include an inclinometer. The valve may include a restrictor valve that is directed by the controller to constrict and reduce hydraulic fluid flow to its connected hydraulic motor when a corresponding side of the lift platform is inclined at least two degrees above or below the opposite side of the lift platform. This slows movement of that motor and the corresponding positively or negatively inclined side of the lift platform until the lift platform achieves a level condition.

In alternative embodiments, each lift cable may be secured or tied off directly to a respective longitudinal side of the lift platform

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages will occur from the following description of a preferred embodiment and the accompanying drawings, in which:

FIG. 1 is a simplified elevational end view of a self-leveling hydraulic motor post-style boat lift according to this invention, which features a pair of hydraulic motors mounted on support posts located on opposite proximal and distal sides of the lift;

FIG. 2 is a simplified elevational and fragmentary, cross-sectional view of a respective winder and interengaged cable assembly employed by the present invention for lifting and lowering the lift platform;

FIG. 3 is a schematic view that illustrates the lift platform leveling system employed by the hydraulic motor driven boat lift;

FIG. 4 is an elevational end view of the hydraulic motor lift in an unbalanced and unlevel condition with the lefthand side of the lift platform inclined relative to the righthand side of the lift platform; and

FIG. 5 is an elevational end view similar to FIGS. 1 and 4 of the lift in an unbalanced and unlevel condition, wherein the right-hand side of the lift platform is inclined relative to the lefthand side of the platform.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

There is shown in FIG. 1, a preferred self-leveling hydraulic motor driven boat lift apparatus 10 that employs at least one pair of hydraulic motors 12 and 14 for selectively raising and lowering a lift platform 16 and supported boat B out of and into a body of water (not shown). It should be understood that the lift can be utilized for virtually all types of boats, vessels and watercraft. The lift may be employed proximately to and/or in conjunction with a dock, pier, seawall, or other marine structure bordering a boat slip or watercraft storage space. The apparatus is suitable for use in virtually any body of water in which a boat lift is normally employed. As illustrated herein, lift 10 is typically intended for use as a post lift, which should be understood to comprise lifts mounted on pilings or posts, as well as free-standing boat lifts that employ an underlying framework or other support structure mounted in a body of water in a manner that will be known to those skilled in the art. For purposes of illustration herein, FIG. 1 discloses support posts or pilings 18, 20 on which are mounted hydraulic motors 12 and 14 and their associated winders and lift cables (described more fully below). Posts 18 and 20 may be composed of various materials, i.e., concrete, metal alloys, wood or any other type of support suitable for use in connection with winder and cable driven boat lifts. The supportive structure of lift 10 may have various numbers of posts and the term “post,” as used herein, may comprise various alternative structures such as pilings, beams, legs, underlying framework, etc. Lift 10 may also be used with proximate supportive structure such as docks, decks piers, etc. The nature and type of the support structure is not a limitation of this invention.

Support post 18 represents a first or proximal support structure on one side of boat B. Post 20 similarly comprises a second or distal support structure that is disposed on the opposite side of boat B. In alternative embodiments, one or more additional pairs of opposing proximal and distal support posts may be formed in a similar manner along the respective sides of the boat and underlying lift platform 16. When boat B is positioned on lift 10, each support post 18 is arranged on a first longitudinal side of the boat and each support post 20 is positioned on the opposite second or distal longitudinal side of the vessel. As previously indicated, the support posts may be replaced by other types and numbers of support structures within the scope of this invention.

Proximal hydraulic motor 12 is mounted atop support post 18 and distal hydraulic motor 14 is similarly mounted atop distal support post 20. Herein, the structure and operation of lift 10 is disclosed for a single pair of opposite hydraulic motors 12 and 14. In alternative embodiments, one or more additional pairs of analogous motors may be formed at corresponding longitudinal positions on opposite sides of the lift and along respective longitudinal sides of the supported boat B. The following description applies analogously to each such additional pair of hydraulic motors.

Each hydraulic motor 12, 14 is operably connected through a gearbox to a corresponding axially rotatable winder mechanism that extends longitudinally on a respective side of the lift and supported boat B. FIG. 2 depicts in cross-section a simplified version of a representative winder mechanism 22 and a lift cable, which is operably connected to and wound about the winder mechanism. Each winder mechanism 22 may be mounted to a longitudinal winder housing or beam 25 that is itself installed across/carried by the support post(s) 16, 18 on a respective longitudinal side of the lift. The lift cable 24 wound on winder mechanism 22 interengages a pulley 26 that is, in turn, secured to lift platform 16. The distal end of cable 24 is tied off to housing 25 or some other point of the lift's support structure by a fastening element 27 or other conventional means of tying off a lift cable.

In alterative embodiments, the winder housing and accommodated winder may be attached directly to and/or depend from a dock, deck or other support structure adjacent to the lift platform. In still other versions, the winder may be operably interengaged with a conventional one-part cable assembly wherein a pulley is not employed and the lift cable is tied off to the lift platform, either to one end of a respective cradle beam or otherwise. In any event, the one part and two part lift cable assemblies described herein, both with and without the pulley, are simple and efficient and do not require the more complex use of multiple directional pulleys and three or more different directional sections of cable. Each winder 22 is operably and axially rotatably connected to either a corresponding proximal hydraulic motor 12 supported on the proximal support post(s) 18, or to a corresponding distal hydraulic motor 14 supported on the distal support post(s).

Lift platform 16 is operably (vertically movably) mounted to proximal and distal support posts 18 and 20 or other support structure. Platform 16 typically comprises at least a pair of lateral cradle beams 28, a representative one of which is shown in FIGS. 1 and 2. Each cradle beam 28 may effectively comprise an I-beam or a similar elongate beam having a pair of channels extending longitudinally on respective forward and rearward sides thereof. The cradle beams may be formed by various known means utilized in the boat lift and marine industries. The cradle beams are composed of aluminum or similar rust and corrosion-resistant material. Each cradle beam may comprise a wide variety of constructions permitting the beams to carry pulleys 26 or cable tie offs on the opposing longitudinal sides of lift platform 16 (FIG. 2), which are operably engaged with respective lift cables 24

Lift platform 16 also includes a parallel pair of elongate bunks 30 and 32 extending transversely or lateraly across cradle beams 28. The bunks extend longitudinally beneath and support boat B. Bunks 30, 32 likewise may be composed of aluminum, wood, or appropriate synthetic materials. They are bolted or otherwise secured to the cradle beams in a known manner. When boat B is mounted on the lift, it sits on the bunks as best shown in FIG. 1. Lift 10 includes at least one pair of lift cable assemblies, as represented in FIG. 2, which operably interconnect hydraulic motors 12 and 14 with respective longitudinal sides of platform 16 and, more particularly, respective longitudinal ends of a respective cradle beam 28. As previously described, each cable assembly features an elongate cable 24 that is interconnected between either a proximal or distal winder 22 and an associated pulley 26 secured to the proximal or distal end of a respective cradle beam 16. As shown in FIG. 2, a simple, yet efficient and effective two-part cable is thereby employed to operably interconnect each hydraulic motor to the lift platform. As used herein, the “lift cable” may comprise multiple or single strand wire, rope or cord, as well as various other types of strong, durable, flexible and preferably corrosion-resistant materials (i.e., chain) suited for use in boat lifts. Each cable should be an elongate, flexible element. The specific composition is not a limitation of this invention.

Each hydraulic motor 12, 14 is supported on a respective piling, support post or other supportive structure by brackets, bolts or other standard means. The motor may optionally be enclosed within a housing, e.g. housing 25, which encloses the respective winder. Hydraulic fluid is provided to each motor 12 and 14 by a respective hydraulic pump 30, 32, shown in FIG. 3. Each motor 12 and 14 is reversible and selectively operable in opposing directions for respectively raising and lowering boat-accommodating lift platform 16. As shown schematically in FIG. 3, as well as in FIGS. 1, 4 and 5, hydraulic pumps 30 and 32 are contained in a control box 34 mounted on or otherwise firmly secured to a dock 36 that is adjacent to lift 10. Dock 36 may also comprise a deck, pier or other supportive structure that is a part of or adjacent to lift 10. Pumps 30 and 32 are mounted within control box 34 and connected by respective hydraulic lines 37 and 38 to hydraulic motors 12 and 14,. The hydraulic lines may be interconnected to the pumps and respective hydraulic motors by conventional hydraulic fittings. The pumps, hydraulic lines and motors are constructed and configured so that the hydraulic motors are selectively operable in opposing directions. Pumps 30 and 32 synchronously operate to transmit hydraulic fluid through hydraulic lines 30, 32 between the pumps and respective hydraulic motors 12 and 14. This, in turn, directs the hydraulic motors to synchronously drive their interengaged winders and cable assemblies in the respective opposing directions required to selectively raise or lower the lift platform and supported boat B as required. In alternative embodiments, hydraulic pumps 30 and 32 may be enclosed in different respective control boxes 34, with each control box being located adjacent a respective support post and hydraulic motor.

The use of at least one pair of hydraulic motors 12 and 14 on respective opposite longitudinal sides of the lift provides lift 10 with a significantly increased and beneficial lifting capacity over existing lifts. Moreover, larger vessels are raised and lowered more easily, quickly and efficiently on lift 10 without requiring complex lift cable and pulley arrangements. Nonetheless, when opposing motors are utilized in the manner shown, and the supported boat B exerts a laterally unbalanced weight load, there is a tendency for the hydraulic motor located on the lighter weight lateral side of the lift platform to raise the lift platform more quickly than the hydraulic motor raising the heavier side of the platform. When the lift is lowered, the heavier side of the lift platform and supported vessel will tend to descend more quickly. Either condition can cause the lift platform to angularly tilt or incline downwardly on either the lefthand side as shown in FIG. 4 or the righthand side as shown in FIG. 5. If such lateral tilt or inclination exceeds a certain angle (e.g., +/−2 degrees) this can seriously interfere with the smooth raising or lowering of the boat. There is a risk that the boat may be damaged during operation of the lift and, in extreme cases, the unevenly supported boat/load may be in danger of dislodging from the lift which could cause catastrophic damage to the boat and/or the lift.

The hydraulic lift of the present invention employs a self-leveling system which addresses and overcomes the foregoing problem. As shown in FIGS. 1 and 3-5, an inclinometer or other angle measuring sensor 40 is mounted to cradle beam 28 or other part of lift platform 16. The inclinometer is electrically interconnected to a controller 42, FIG. 3, which is mounted within control box 34. Controller 42 is electrically connected to restrictor valves 44 and 46 within control box 34. The restrictor valves 44 and 46 are themselves communicably interconnected to the hydraulic lines communicably connecting hydraulic pumps 30 and 32 to proximal hydraulic motor 14 and distal hydraulic motor 16, respectively.

In operation, hydraulic motors 14 and 16 are operated to turn the respective winders 22 so that interengaged cables 24 and pulleys 26 operate to either lift of lower lift platform 16, depending upon the direction (raising or lowering) in which the motor is operated. When the weight of the supported boat B is imbalanced, as shown in either FIG. 4 or FIG. 5, lift platform 16 may become unlevel. The condition shown in FIG. 4 occurs during raising or lowering of the boat when the righthand side of the vessel is heavier. Conversely, when the lefthand side of the vessel is heavier, platform 16 and boat B may be inclined downwardly from right to left during the raising or lowering of the boat as shown in FIG. 5.

To address and rectify the potential problem described above, inclinometer 40 monitors the lateral inclination of platform 16 during the raising and lowering operations. It senses the inclination and sends a signal through line 50 to controller 42. The controller is programmed to receive and process angular inclination signals from inclinometer 40 and provide output signals via lines 52 and 54 to hydraulic restrictor valves 44 and 46, which control the flow of hydraulic fluid between pumps 30 and 32 and hydraulic motors 14 and 16, respectively. The controller may be programmed to adjust the hydraulic flow through one or both of the valves whenever the inclinometer senses that a predetermined inclination angle Is exceeded. For example, if the inclinometer senses that the lateral inclination of platform 16 exceeds +/−2 degrees, controller 42 may be programmed to restrict the flow through one of the valves 44 or 46 so that its respective motor 14, 16 slows. This allows the other side to accelerate until there is a zero lateral inclination angle between the opposing longitudinal sides of the lift platform and the platform is therefore laterally level. As a result, the supported boat is maintained in a safe and level condition while being raised or lowered. Referring to FIG. 4, for example, and the diagram shown in FIG. 3, where the lift platform is being raised and inclinometer 40 senses an inclination of over 2 degrees, controller 42 sends a signal to valve 44 which slows proximal motor 14 and the speed of the lefthand side of platform 16 until the increased relative speed of motor 16 pulls the righthand side of the lift platform level with the lefthand side. Analogously, in circumstances where the inclination depicted in FIG. 5 is exhibited during elevation of the boat. Inclinometer 40 sends a signal to controller 42 which in turn processes the signal and directs valve 46 to slow operation of distal motor 16 until the lefthand side of platform 16 catches up to the righthand side and the platform exhibits a zero degree inclination and a level condition.

Where the inclinometer detects that an imbalanced vessel weight produces a predetermined degree of lateral inclination during lowering of the lift platform, controller 42 is programmed to direct the valve connected to the motor on the negatively inclined side of the platform to analogously slow the flow of hydraulic fluid to that motor. This, in turn, slows the descent of the negatively inclined side of the lift platform until the lift platform achieves a stable and safe level condition.

In alternative embodiments, the controller may be programmed to self-level in the foregoing manner when various other inclination angles are sensed. It should also be understood that in alternative embodiments, the controller may be programmed to direct the valves to increase flow. Nonetheless, in situations where an unbalanced vessel is being lifted, a restrictor valve is preferred because it simply allows the motor on the positively inclined side to be slowed until the other side catches up and the lift platform and supported vessel are brought into a desired level condition. As indicated above, during lowering of the lift platform, a negatively inclined side of the lift platform is similarly slowed to rectify an unlevel condition.

Accordingly, the present invention provides significant benefits. It permits a winder and cable driven post lift to be operated more effectively using hydraulic motors that are much less susceptible than electric motors to deterioration and damage from a wet and severe marine environment. In addition, the use of the hydraulic motors permits the lift to have a lower profile and to be used more effectively in shallow water conditions. The use of multiple hydraulic motors on opposing sides provides the lift with improved lifting capacity and the ability to accommodate larger vessels. In addition, the self-leveling system disclosed herein better enables the hydraulic motors positioned on opposing sides of the lift to maintain the lift platform and supported vessel in a safe and secure level condition during operation of the lift.

While this detailed description has set forth particularly preferred embodiments of the apparatus of this invention, numerous modifications and variations of the structure of this invention, all within the scope of the invention, will readily occur to those skilled in the art. Accordingly, it is understood that this description is illustrative only of the principles of the invention and is not limitative thereof. Although specific features of the invention are shown in some of the drawings and not others, this is for convenience only, as each feature may be combined with any and all of the other features in accordance with this invention.

Claims

1. A hydraulic motor driven boat lift for selectively lifting a boat out of and lowering the boat into a body of water, said boat lift comprising: spaced apart proximal and distal support structures disposed on respective longitudinal sides of a lift platform, which lift platform is adapted for supporting the boat thereon;proximal and distal hydraulic motors respectively mounted to the proximal and distal support structures, said proximal and distal hydraulic motors being operably connected to respective winder mechanisms;a plurality of lift cable assemblies, each said lift cable assembly being operably interconnected between a respective winder mechanism and said lift platform; anda plurality of hydraulic pumps, each said hydraulic pump being communicably connected to a respective one of said proximal and distal hydraulic motors for transmitting hydraulic fluid between said pump and said respective one of said proximal and distal hydraulic motors such that said hydraulic pumps operate said proximal and distal hydraulic motors and drive said respective winder mechanisms and operably interconnected cable assemblies to selectively lift and lower said lift platform.

2. A self-leveling hydraulic motor driven boat lift for selectively lifting a boat out of and lowering the boat into a body of water, the boat lift comprising: spaced apart proximal and distal support structures disposed on respective proximal and distal longitudinal sides of a lift platform, which lift platform is adapted for supporting the boat thereon;proximal and distal hydraulic motors respectively mounted to the proximal and distal support structures, said proximal and distal hydraulic motors being operably connected to respective winder mechanisms;a plurality of lift cable assemblies, each said lift cable assembly being operably interconnected between a respective winder mechanism and said lift platform;a plurality of hydraulic pumps, each said hydraulic pump being communicably connected to a respective one of said proximal and distal hydraulic motors for transmitting hydraulic fluid between said pump and said respective one of said proximal and distal hydraulic motors such that said hydraulic pumps operate said proximal and distal hydraulic motors and drive said respective winder mechanisms and operably interconnected cable assemblies to selectively lift and lower said lift platform;a sensor for measuring lateral inclination between said proximal and distal longitudinal sides of said lift platform;a plurality of hydraulic valves, each said hydraulic valve communicably interconnecting a respective hydraulic pump and said hydraulic motor connected to said pump; anda controller responsive to signals form said sensor for selectively opening and closing at least one said valve a selected amount for adjusting the transmission of hydraulic fluid between at least one said hydraulic pump and a respective said hydraulic motor communicably connected to said hydraulic pump, whereby an operating speed of one or more of said proximal and distal hydraulic motors is adjusted to lateral level said lift platform.

3. The boat lift of claim 2 in which said angle measuring sensor includes an Inclinometer mounted on said lift platform.

4. The boat lift of claim 2 in which said valve includes a restrictor valve that is directed by said controller to constrict and reduce hydraulic fluid flow between said hydraulic pump and said connected hydraulic motor when a corresponding one of said proximal and distal longitudinal sides of said lift platform is laterally inclined at least two degrees relative to an opposite longitudinal side of said lift platform.

5. A self-leveling system for a hydraulic motor driven boat lift, which boat lift includes spaced apart proximal and distal support structures disposed on respective proximal and distal longitudinal sides of a lift platform, which lift platform is adapted for supporting the boat thereon, the boat lift further including proximal and distal hydraulic motors respectively mounted to the proximal and distal support structures, the proximal and distal hydraulic motors being operably connected to respective winder mechanisms, the boat lift further having a plurality of lift cable assemblies, each lift cable assembly being operably interconnected between a respective winder mechanism and the lift platform, and the boat lift further having a plurality of hydraulic pumps, each hydraulic pump being communicably connected to a respective one of the proximal and distal hydraulic motors for transmitting hydraulic fluid between the pump and a respective one of said proximal and distal hydraulic motors such that the hydraulic pumps operate the proximal and distal hydraulic motors and drive the respective winder mechanisms and operably interconnected cable assemblies to selectively lift and lower the lift platform, the self-leveling system comprising: a sensor for measuring lateral inclination between said proximal and distal longitudinal sides of said lift platform;a plurality of hydraulic valves, each said hydraulic valve communicably interconnecting a respective hydraulic pump and said hydraulic motor connected to said pump; anda controller responsive to signals form said sensor for selectively opening and closing at least one said valve a selected amount for adjusting the transmission of hydraulic fluid between at least one one said hydraulic pump and a respective said hydraulic motor communicably connected to said hydraulic pump, whereby an operating speed of one or more of said proximal and distal hydraulic motors is adjusted to lateral level said lift platform.

6. The self-leveling system of claim 5 in which said angle measuring sensor includes an Inclinometer mounted on said lift platform.

7. The self-leveling system of claim 5 in which said valve includes a restrictor valve that is directed by said controller to constrict and reduce hydraulic fluid flow between said hydraulic pump and said connected hydraulic motor when a corresponding one of said proximal and distal longitudinal sides of said lift platform is laterally inclined at least two degrees relative to an opposite longitudinal side of said lift platform.

8. The boat lift of claim 2 in which said sensor includes an inclinometer.

9. The self-leveling system of claim 5 in which said sensor includes an inclinometer.