Abstract:
The present invention relates to a boat lift including a base structure a cradle connected with the base structure and configured to support a boat, and a plurality of pontoons connected with the base structure for floating the boat lift on a water surface. The pontoons include a plurality of modular floats such that boats of varying weights are lifted and boats of varying centers of gravity are lifted levelly. The present invention also relates to a method of employing the boat lift.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to the field of boat docking, and specifically concerns a modular boat lift which is supported by floating it on the water surface using side pontoons comprised of modular floats 
   2. Description of the Prior Art 
   The mooring of a boat or ship at a dock with the use of mooring lines has been known for hundreds of years. But it was not until the relatively recent past that means became available to readily raise a boat out of the water when not in use. Since the typical pleasure boat spends nearly its entire life not in use, it is highly desirable to remove the boat hull and running gear from the water whet it is not being used. This is true regardless of whether the boat is in fresh water or salt water. In fresh water algae tends to grow on the hull, while in salt water there is the growth of barnacles and other types of sea life on the hull and electrolysis often harms metal components of the boat, e.g., propellers, shafts, trim tabs, rudders and engine seals. 
   A great variety of devices have been employed for this purpose. One device uses davits on a dock or seawall in which books are attached to cleats on the boat and cables connected to a winch powered by electric motors that then lift the boat out of the water by brute force. It is also quite commonly known that these devices are ugly, fairly noisy, and are very dangerous if a cable parts. As a consequence, many residential communities do not permit their use. 
   There are a variety of patented devices that have been used to lift boats from the water. An example is Dettlang, Jr., U.S. Pat. No. 5,238,324, which teaches a combination wheeled boat dock and lift by which a boat is virtually driven around a body of water. Another example is Thomas, U.S. Pat. No. 4,686,920, which teaches a cradle type of device submerged in the water between pilings and then lifted using block and tackle powered by an electric motor. Another example is Sackett, U.S. Pat. No. 5,131,342, which discloses a shallow draft floating boat lift which employs two pontoon type flotation chambers on either side of the hull wherein lift is created using jack screws powered by electric motors. 
   The general concept of the use of flotation devices in combination with mechanical apparatus to achieve lifting a boat from the water, as in the present invention, is known. An example is Gates, U.S. Pat. No. 6,032,601, which also employs pontoons on either side of the boat with a cradle therebetween. However, this reference significantly differs from the present invention, in part because this reference employs pivoting arm structures and a drive mechanism that use potentially dangerous and noisy cables to raise the boat relative to the pontoons so that the hull emerges from the water. Other distinctions with this reference will become apparent upon review of the following detailed descriptions of the present invention. 
   Another prior art reference is Dickman, U.S. Pat. No. 5,979,349, which uses a tank with air and water levels in that tank being adjustable to raise and lower the lift. However, it also employs a dock attached jackscrew to reduce and minimize listing of the boat bull and adjusting air tube that allegedly affects listing as well. 
   Another approach is to employ a floating platform having a v-shape in the center thereof, a series of rollers at the bottom of the V-shape corresponding to the position of a keel on a V-hull and a winch with is capable of pulling the boat out of the water and on to the top of what amounts to a floating dock. This approach is taught by Hillman, et al, in U.S. Pat. No. 6,006,687. 
   Some prior art devices have used means of changing buoyancy of certain components to achieve submergence and lifting. An example of that approach is a patent issued to Siegmann, U.S. Pat. No. 6,257,159, which is an apparatus for raising and lowering boats in water that has the capability of lifting a center keel sailboat completely out of the water. It employs flotation tanks or chambers that are alternately flooded or evacuated using compressed air and which further employs an elaborate structure of eight traction mechanisms in the form of reels and apparent cables to assist in the lift effort. Siegmann represents a very complex invention. 
   Moody, U.S. Pat. No. 5,860,379, teaches an inflatable floating boat lift device constructed of a flexible impermeable fabric comprising main air chambers and a network of hoses and blowers which control the inflation and deflation of each main chamber independently. This device provides vertical lifting of the boat while floating on the surface of the water. The blower is operated either by 115 volt AC, or 12 or 24 volt DC power. 
   A further reference of interest that is somewhat older is Bradfield, U.S. Pat. No. 3,967,570, which is a floating boat dock lift that employs a variable buoyancy chamber connected to an air pump and valves. It also employs a hinged structure to the dock. 
   Yet another reference is that of Samoian, et al., U.S. Pat. No. 5,485,798, which discloses a floating boat lift supported by side pontoons and having a cradle lifted by the operation of hydraulic cylinders that employ water rather than hydraulic fluid, and use a parallelogram linkage in combination with the hydraulic cylinders. Samoian, et al. does not teach the modular concept or any other means to expand its boat weight handling capability. 
   Accordingly, what is needed is a method and apparatus to overcome some of the shortcomings and problems with the prior art. Particularly, what is needed is a boat lift with the ability to expand the size of boat lift while offering at the same time simplicity, silent operation, and low visibility of the present invention. The latter features are important because in many communities, boat lift devices are banned because of their unsightliness, potential pollution considerations, consumption of space, use of water contaminating underwater devices, noise and for numerous other reasons. Noise is a consideration because the prior art that uses buoyancy tanks does so with air pumping devices such as vacuum cleaner pumps and motors that are notoriously noisy. 
   SUMMARY OF THE INVENTION 
   The present invention is an improvement patent over Samoian, et al. in that it employs a modular concept regarding many of its parts to allow the boat lift to be varied to accommodate heavier boats without having to be completely replaced. This concept is important because the typical boat owner keeps buying bigger and heavier boats as time goes by, and the present invention is focused on the means to accommodate such growth in boat weight without requiring replacement boat lift. 
   The lift mechanism includes a parallelogram linkage supporting a cradle. The structure, in addition to the floats, is also modular or adjustable so that the capacity of the lift is readily alterable to accommodate heavier or lighter boats, and this is done in the field. 
   The parallelogram linkage is pivoted into a flattened configuration when a boat is being launched. The cradle portion of the modular boat lift mechanism includes surfaces known as boat bunks, normally covered with carpet, which contact the boat hull and raise it silently out of the water by the use of the parallelogram linkage when latter is pivoted into its expanded configuration by at least one aqueous hydraulic cylinder, but almost invariably a plurality thereof. The power source for the aqueous hydraulic cylinders is a conventional hose bib and water pump and accompanying controls. The use of household water is preferred, but ambient water is useable also. 
   Significant resulting advantages of the invention are (1) that the modular boat lift is modified in size in the field to accommodate heavier or lighter boats (2) taken in combination with point (1) there is no aspect of the structure which contaminates environmentally sensitive waters because the power source uses only ambient or household water to operate the hydraulic cylinders, not hydraulic fluid, and (3) taken in combination with point (1) that the operation of the modular boat lift is almost totally silent because the only sound is that of a water pump, and even that sound is muffled when placed in a acoustically insulated dock box. The modified boat lift is so quiet in operation that it is equipped with a strobe light to signal that it is in operation. 
   The inventive modular boat lift is simply towed to its operating locale and either secured to a dock with conventional mooring lines and/or otherwise secured with eyelets attached to pilings, bulkheads, or other waterside structures. Alternative means to position the lift are also envisioned, even one or more anchors. This avoids the construction of unsightly permanent structures such as davits at the waterside and minimizes or eliminates the expense and delay involved in securing regulatory approval for the construction of such permanent structures. When a size change is needed, the modular boat lift is raised out the water on site, the size changes made, and the lift returned to the water on site. This requires lifting equipment on site. More commonly the lift is towed to a boat yard equipped with a travelift. 
   The modular boat lift features a low profile because the lift mechanism is submerged when not in use. This leaves only modular float pontoons supporting the boat lift, its mooring lines, and its water pump power source dock box visible, except when a boat has been lifted out of the water. Further, even when the lift is in use supporting a boat out of the water, it is also relatively low profile because the cradle is smaller than the length and beam dimensions of the boat hull and only the upper portions of the expanded parallelogram linkage are visible. 
   Bearing in mind the foregoing, the present invention provides a modularly expandable, submerged pontoon supported boat lift apparatus and method that, except for the pontoons, mooring lines, and a dock box, is of very low visibility, with the lift mechanism itself being submerged beneath the water surface, except for boat bunks and about six (6) inches of lifting lever being barely visible when supporting a boat out of the water. 
   In one embodiment, the present invention provides a modularly expandable, pontoon supported submerged boat lift apparatus and method which employs nothing that contaminates or fouls the water in which it is operated. 
   In another embodiment, the present invention provides a modularly expandable pontoon supported submerged boat lift apparatus and method which employs very few moving parts, those being a water pump, four solenoid valves, aqueous hydraulic cylinders and locking mechanisms attached to each cylinder. 
   In a further embodiment, the present invention provides a modularly expandable pontoon supported submerged boat lift that employs as a power source, household water, or optionally the very same ambient water in which the apparatus is deployed. 
   In another embodiment, the present invention employs inert materials in the water which do not foul the environment, or require maintenance in a modularly expandable boat lift. 
   In a further embodiment, the present invention provides a modularly expandable pontoon supported submerged boat lift which requires no special mechanism for affixing to the dock in that it is simply tied to a boat dock with mooring lines in the same manner as a boat, which results in part from the invention&#39;s level lift capability. 
   The present invention also provides a modularly expandable pontoon supported submerged boat lift having level lift capability because the pontoons are moveable in the field to accommodate a differing CG in different boats. 
   In a further embodiment, the present invention enables the apparatus to be towed to its operating location, thus avoiding the construction of permanent structures such as davits with the common accompaniment of delay and expense of obtaining regulatory approval that such permanent structures often require, and which is modularly expandable in the field. 
   In another embodiment, the present invention permits moving the boat lift to more than one location, such as when a boat owner with waterfront property moves to another waterfront property. 
   In yet another embodiment, the present invention provides a boat lift capability that is suitable for use with a wide variety of boat weights and hull types all in a level lift configuration, including V-hulls and catamarans of a variety of lengths with a capability of handling a boat up to about 20,000 pounds presently, and with substantial addition capacity contemplated, because the design is modular to accommodate various design hulls and displacement weights. 
   The present invention further provides a modularly expandable floating boat lift that is operable either from within the boat or on the dock using a remote that is attachable to the key ring of the boat key or using a switch disposed within the dock box. 
   In another embodiment, the present invention provides a modularly expandable floating boat lift having at least one aqueous hydraulic cylinder as the power source for the boat cradle and wherein there are mechanical locking mechanisms for each aqueous hydraulic cylinder to lock the lift at the highest point to assure that pressure need not be maintained in the aqueous hydraulic cylinder(s). 
   In accordance with the major aspect of the invention, there are provided a plurality of modular floats that make up boat lift supporting pontoons of variable length to accommodate boats of different weight, in combination with an expandable parallelogram linkage supporting a cradle between the pontoons, which linkage is operated by at least one, and preferably by two or more aqueous hydraulic cylinders powered by a water pump and conventional controls that include a remote such as used to activate an automatic garage door opener. The water pump preferably uses household water from a hose bib which is discharged in the ambient water. Alternatively, an inlet hose disposed beneath the ambient water surface is used and equipped with a sea strainer such that the pump, solenoid valves, aqueous hydraulic cylinders and connecting hoses are kept free of debris. The water pump is preferably controlled by the remote which is attachable to the key ring of the boat or a switch in the dock box. The remote controls not only the water pump operation, but also solenoid valves in the water lines, such as between the pump and the aqueous cylinders to maintain water level in the cylinders at a fixed point. Mechanical locking mechanisms are also preferably employed to assure the boat will be maintained in its lifted position. 
   In operation the boat will be driven to dockside and between the pontoons. The pontoons act as guides to precisely position the boat directly over the cradle. The pump and the solenoid valves are then activated within the boat using the remote. The water pump will start and pump water into the aqueous hydraulic cylinders through the connecting hoses. The pistons of the hydraulic cylinders, which are attached to devises on the vertical legs of the parallelogram linkage, will then begin to extend the parallelogram from its collapsed configuration such that the carpeted boat bunks on the cradle come in contact with the submerged portion of the boat hull. Continued operation of the water pump raises the parallelogram linkage to its most erect configuration, such that the boat hull has been raised so that it is entirely clear of the water. The water pump is then shut off, the solenoid valves closed, and the locking mechanisms activated. 
   When it is desired to use the boat, the boat is boarded, the solenoid valves are initially opened to raise the boat slightly so that the locking mechanisms are withdrawn from the cylinder pistons, the solenoid valves are then activated to reverse the direction of water flow so that the single direction water pump evacuates water from the hydraulic cylinders to retract the hydraulic cylinder pistons, which collapse the parallelogram linkages and lower the boat into the water so it floats free of the cradle. The cradle is lowered to its most retracted point because the parallelogram linkage is collapsed to its maximum point. The entire apparatus disappears beneath the water except for the pontoons, mooring lines and dock box containing the water pump, solenoid, check and pressure relief valves, and related controls. 
   The present invention is of modular design so that the capacity of the boat lift is alterable to vary its capacity to accommodate heavier or lighter boats, which is done in the field. The distance between pontoons is adjustable, and the distance between the sides of the cradle, called boat bunks, is variable. The height of the boat bunks is indirectly variable by changing the length of vertical support columns that connect the pontoon to the remainder of the structure. The pontoons accommodate variations in the center of gravity (CG) of the boat in question by shifting the pontoons forward or aft. 
   The pontoons are comprised of an array of four foot long segments called modular floats having channel float beam flange tracks molded into their lower surface so they slide onto the upper flange of a supporting channel float beam. The length of the channel float beam is extendable and additional modular floats are added. The parallelogram linkage is also extendable by having additional parallelograms added along with further hydraulic cylinders. The modular floats move forward or aft to achieve level lift as a result of accommodating the boat CG. In short, then entire structure is designed to expand (or contract), and this is readily achieved in the field. 
   Reference will now be had to the drawings in which: 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     While the specification concludes with claims defining the features of the invention that are regarded as novel, it is believed that the invention will be better understood from a consideration of the following description in conjunction with the drawing figures, in which like reference numerals are carried forward. 
       FIG. 1  is an overhead perspective view of the modular floating boat lift, with the cradle shown at its most erect position. The modular boat lift is shown for clarity without ambient water, cradle reinforcing members or a boat on the cradle. 
       FIG. 2  is a side elevation view of the parallelogram linkage that supports the cradle of  FIG. 1 , but with the parallelogram linkage partially collapsed. 
       FIG. 3  is another side elevation view of the parallelogram linkage that supports the cradle of  FIG. 1 , but with the parallelogram linkage substantially fully collapsed. 
       FIG. 4  is a broken end view of one of the pontoons as seen in  FIG. 1  showing its support by channel float beams in spaced relationship using a long bolt, spacer, and with the vertical support column shown in phantom. 
       FIG. 5  is a broken enlarged perspective view of a portion of a pontoon showing how the tops of the adjoining floats are attached to each other. 
       FIG. 6  is a broken front elevation view of a channel float beam showing that the various beams in the structure of  FIG. 1  are also modular, being a series of pieces held together with joining plates bolted to the pieces. 
       FIG. 7  is a vertical support column showing it is perforated along the lower portion of its length so that its length is alterable using a bolt that attaches it to the base structure. 
       FIG. 8  is a broken enlarged view of the end of a aqueous hydraulic cylinder showing the operating portion of the locking mechanism to fix the cylinder piston in the extended position so that a boat raised on the lift is positively secured in that position without regard to the maintenance of pressure in the hydraulic cylinder. 
       FIG. 9  is a side elevation view of the control lever that directs the operation of the locking mechanism of FIG.  8 . 
       FIG. 10  is a top plan view of the control lever of  FIG. 9  showing the handle and cable connecting cross member that controls the position of the cables which in turn direct the operation of the locking mechanism of FIG.  8 . 
       FIG. 11  is a perspective view of the modular boat lift placed in the water at a dock, with a boat raised out of the water on the lift cradle. 
       FIG. 12  is a front elevation view, looking slightly upward and showing the support of the boat of  FIG. 11  high and dry on the cradle. 
       FIG. 13  is a schematic drawing of the dock box, its connection to the hydraulic cylinders, and the key with remote, the latter of which operates the lift. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   A detailed embodiment of the present invention is disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for, the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. Moreover, some statements may apply to some inventive features but not to others. In general, unless otherwise indicated, singular elements may be in the plural and vice versa with no loss of generality. In these figures, for the sake of clarity, the dimensions of the various component parts shown have not been drawn to scale. 
   Reference now is made again to the drawings, wherein like characteristics and features of the present invention shown in the various figures are designated by the same reference numerals. 
     FIG. 1  is an overhead perspective view of the modular floating boat lift  10 , with the cradle  12  shown at its most erect position. The modular boat lift  10  is shown for clarity without ambient water, cradle reinforcing members or a boat on the cradle. The boat lift  10  floats in water because of pontoons  14  that are comprised of a plurality of modular floats  16 . The cradle  12  is comprised of boat bunks  18  and  20  which contact and support the bottom of a boat hull as seen and described later in regard to  FIGS. 11 and 12 . The boat bunks  18  and  20  are preferably covered with carpet to minimize marking of or damage to the hull of the boat. Although not shown, the boat bunks  18  and  20  are two or more segments hinged together to accommodate the curvature of the hull. 
   The cradle  12  is raised and lowered using the force of aqueous hydraulic cylinders  22  which are hingedly connected at both ends to other portions of the structure. The base end  24  of the aqueous hydraulic cylinder  22  is connected to the base structure shown generally at  26 . The base structure  26  is comprised of two or more base cross beams  28  and two or more base longitudinal beams  30 . The distance between the base longitudinal beams  30  is adjustable because hinged sleeve bracket  32  move left or right along base cross beams  28 . The pontoons  14  are interconnected with the base cross beams  28  using vertical support columns  34 . As later seen in  FIG. 7  the height of the vertical support columns  34  are modifiable because doing so indirectly controls the height of the boat bunk  18  and  20 . The distance between pontoons  14  is similarly adjustable because vertical sleeve brackets  36  also move left or right along the base cross beams  28 . The pontoons  14  shift forward and aft to accommodate boat CG to achieve level lift, enabling the entire modular boat lift to be simply tied up to a dock with conventional mooring lines  90 , as seen in FIG.  11 . Level lift also avoids undesired movement of loose objects in the boat. The ends of the pontoons  14  are cantilevered from the outside vertical support columns  34 , which create an upward bending moment on these cantilevered ends. This upward bending moment on the cantilevered ends is countered by wire rope or cables  35 . 
   The upper end  38  of the aqueous hydraulic cylinders  22  includes a piston  40 , which is connected at a hinge  42  to a lifting lever  44 . A plurality of lifting levers  44  are disposed parallel to each other and support cradle  12  and its boat bunks  18  and  20 . The combination of lifting levers  44 , their hinged connection at  46  to cradle  12 , and the hinged connection at  48  to the longitudinal base beams  30  form a parallelogram linkage as will be more easily seen in  FIGS. 2 and 3 . 
     FIG. 2  is a side elevation view of the parallelogram linkage that supports the cradle of  FIG. 1 , but with the parallelogram linkage partially collapsed. Seen are lifting levers  44  disposed parallel to each other, their hinged connection at  46  to cradle  12 , half of support cradle  12  comprising boat bunk  18 , and the hinged connection at  48  to the longitudinal base beams  30  comprise the parallelogram linkage. 
     FIG. 3  is another side elevation view of the parallelogram linkage that supports the cradle of  FIG. 1 , but with the parallelogram linkage substantially filly collapsed. The same parts are seen as illustrated in FIG.  2 . 
     FIG. 4  is a broken end view of one of the pontoons  14  as seen in  FIG. 1  showing its support by channel float beams  50  in spaced relationship using a long bolt  52 , preferably eighteen inches, and hollow spacer  57 . Also seen are flange  56  of the channel float beam  50  disposed within a mating groove  58  of the end modular float  16  of the pontoon  14 , and also showing how the channel float beam  50  is supported and positioned on the long bolt  52  by nut  60 . Washers of conventional design are also used but are not shown. A unique feature of the present invention is the fact that the flange  56  of the channel float beam  50  constitutes a sliding track which operates in relationship with the mating groove  58  of the modular floats  16  for initial assembly of modular boat lift  10 , and for modular enlargement or contraction of the lift as needed. Floats are adjusted forward or aft relative to the boat position to properly locate the CG of the boat. The invention includes specific instructions on how to establish the CG of the boat and adjust the floats forward or aft. This feature permits level lift, leading to at least two advantages. The first is that the modular boat lift  10  is simply tied to a dock with conventional mooring lines. The second is that level lift means loose objects in the boat, such as the personal possessions of the boat users do not have to be secured or tied down. Vertical support column  34  and vertical support column bracket  54  are also shown in phantom. 
     FIG. 5  is a broken enlarged view of pontoon  14  showing a plurality modular floats  16 . At the top of the modular floats  16  are disposed face plates  61  on all four upper corners of each float. Passing between each pair of adjacent floats are float rods  63  seen in phantom, and attached to the face plates  61  at bolt  65 . 
     FIG. 6  is a broken font elevation view of a channel float beam  50  showing that the various beams in the structure of  FIG. 1  are also modular, being a series of pieces  62  and  64  held together at a joint  66  with joining plates  68  bolted to the pieces  62  and  64 . While  FIG. 6  shows a channel float beam  50 , it is intended to illustrate that this principle is applied throughout the entire structure of the modular boat lift, since the same result is achieved with such things as boat bunks  18  and  20 , base cross beams  28 , and base longitudinal beams  30 . This is, of course, part of what makes the design truly modular. Other features that contribute to that achievement are the fact that the pontoons are comprised of modular floats  16 , the modular floats are adjustable forward and aft to accommodate boat CG so level lift is achieved allowing the modular boat lift  10  to be simply secured with mooring lines  90  and avoiding shifting of loose objects on board the boat, the distance between the base longitudinal beams  30  is adjustable, the distance between pontoons  14  is adjustable, and the height of the boat bunks  18 ,  20  is similarly adjustable. This latter feature results from the fact that the vertical support column  34  as seen in  FIG. 7  is perforated along the lower portion of its length  45  so that its length is alterable using a bolt  47  that attaches it to hinged sleeve bracket  32 . The effect of changing the length of vertical support columns  34  is to change the vertical position of the pontoons  14  relative to the remainder of the structure. Since the entire modular boat lift  10  floats in ambient water  86  as seen in  FIG. 11 , changing the vertical position of the pontoons  14  results in changing the height of the boat bunks  18  and  20 . 
   This concept of modularity is of importance to the industry of boat lifts because of the commonly known fact that boat owners keep buying bigger and heavier boats and they don&#39;t want to have to keep buying completely new boat lifts. The same concept is of importance to the patentability of this invention because modularity is not found anywhere in the prior art known to Applicant. 
     FIG. 8  is a broken enlarged view of the upper end  38  of one of the aqueous hydraulic cylinders  22  showing the operating portion of the locking mechanism  70  to fix the cylinder piston  40  in the extended position so that a boat raised on the lift is positively secured in that position without regard to the maintenance of pressure in the hydraulic cylinder  22 . Cylinder piston  40  includes a shallow bore  72 , but in  FIG. 8  piston  40  is hyperextended just to reveal shallow bore  72 . In practice, it would not be seen because the farthest out it would travel would be inside housing  74 , where it would be disposed in registration with pin member  76  when the cylinder piston  40  is fully extended. This condition of a fully extended cylinder piston  40  corresponds to the raising of the parallelogram linkage to its maximum height, which in turn means that the boat lift  10  has raised the boat high and dry out of the water as shown in  FIGS. 11 and 12 . Pin member  76  slides up and down in tube  78  to go in and out of shallow bore  72 . Tube  78  is welded to housing  74 . The position of pin member  76  is determined by its connection to cable  80 . Cable  80  moves within cable sheathing  82 . While  FIG. 8  shows the locking mechanism at one hydraulic cylinder  22 , the same structure is repeated at each hydraulic cylinder  22 . 
     FIG. 9  is a side elevation view of a control lever  84  that directs the operation of the locks of the locking mechanism  70  of FIG.  8 . Control lever  84  pivots about axle  86  and is connected to the opposite end of cable  80 . Cable  80  is disposed within cable sheathing  82 . Thus, by moving control lever  84  up or down, cable  80  moves pivoting member  76  such that stud  74  engages and disengages with shallow bore  72 , thereby locking and unlocking the fully extended cylinder piston  40  of aqueous hydraulic cylinder  22 . Again, this is typical of the control levers that operate locking mechanisms at each hydraulic cylinder  22 . Included is bore  89  suitable for mounting control lever  84  to float rods  63  and bolts  65  at face plates  61  as seen in FIG.  5 . Boat lift cleats  94  for mooring lines  90  to position the modular boat lift  10  in respect to dock  88  are seen in  FIG. 11 , but it is useful to know that boat lift cleats  94  are similarly attached to pontoons  14  using float rods  63  and bolts  65  at face plates  61  as seen in FIG.  5 . 
     FIG. 10  is a top plan view of the control lever  84  of  FIG. 9  showing the handle  85  and cable connecting cross member  87  that controls the position of the cables  80  which in turn direct the operation of the locking mechanisms of FIG.  8 . In this instance, four cables  80  are shown on connecting cross member  87  because the unit in question has four hydraulic cylinders. 
     FIG. 11  is a perspective view of the modular boat lift  10  placed in the water  86  at a dock  88 . The modular boat lift  10  is shown positioned and retained using mooring lines  90  tied to dock cleats  92  and boat lift cleats  94 , but it will be understood that other means are available to hold the modular boat lift. This includes, but is not limited to, mooring whips, pilings, anchors, and various fixed or floating structures. A boat  96  is shown raised high and dry out of the water  86  on the lift cradle  12  supported by lift levers  44 . A dock box  98  is shown on dock  88 . Dock box  98  contains a plurality of components relating to the operation of the modular boat lift  10 , which are schematically described in FIG.  13 . 
     FIG. 12  is a front elevation view of the boat  96  from the bow, looking slightly upward, and illustrating the support of the boat  96  of  FIG. 11  high and dry on the cradle  12 . In this view boat bunks  18  and  20  are seen supported on the upper ends of lift levers  44  above the surface of the water  86 . 
   Turning finally to  FIG. 13 , dock box  98  is schematically shown, with components contained therein also illustrated schematically. Also seen is boat key  100  with remote  102 . Remote  102  is one way to control the contents of the dock box  98 , the other being a manual switch of conventional nature and not shown. Further illustrated is water piping  104  to aqueous hydraulic cylinders  22  shown in broken view, incoming electrical power  106  and incoming household water  108 . 
   The dock box  98  also contains an RF (Radio Frequency) antenna  110  and receiver  112  for receiving RF signals  114  from the remote  102 , which is equipped with up  116  and down  118  buttons. The RF antenna  110  and receiver  112  are connected to an electrical switch  120 . Electrical switch  120  is in electrical communication to various electrical components in the dock box, including especially water pump  122 , through conventional power lines not shown. Electrical switch  120  also includes a conventional timer that shuts off everything five (5) minutes after a boat has been lowered into the ambient water. Since water pump  122  operates only in one direction, reversing its pumping direction is accomplished with piping and solenoid valves, as now described. 
   Tracking downstream from incoming water  108  inlet  124  is disposed solenoid valve  126  to close off and open the water line  108  from inlet  124 . The solenoid valve  126  is controlled by electrical switch  120 . Downstream of solenoid valve  126  there a check valve  128  to ensure that water does not back up from solenoid valve  144 , whose function and location are later described. 
   Following after check valve  128 , water line  130  connects to pump  122  inlet tee  132 . After water passes through pump  122 , it is discharged through outlet tee  134 . Inlet tee  132  and outlet tee  134  accept and direct water respectively depending upon which solenoid valves are opened or closed for the purpose of pumping water into or out of aqueous hydraulic cylinders  22 . For example, when solenoid valve  136  is closed, outlet tee  134  is directed along water line  138  to solenoid valve  140 , which is open when solenoid valve  136  is closed and water is being pumped to the cylinders  22  through water lines  104 . After exiting solenoid valve  140 , a check valve  142  prevents back flow to the pump  122 . 
   When it is desired to evacuate water from the hydraulic cylinders  22 , solenoid valves  126  and  140  are closed. Solenoid valves  144  and  136  are opened. Water in water lines  104  then passes through solenoid valve  144 , and water line  146  to pump  122  inlet tee  132 , through pump  122 , through outlet tee  134 , water line  148 , through solenoid valve  136  to discharge  150 . Note that regardless of whether water pump  122  is pumping water into the cylinders  22  as when solenoid valves  126  and  140  are open, or out of the cylinders  22  as when solenoid valves  144  and  136  are open, water always passes through the pump  122  in the same direction, i.e., from inlet tee  132  to outlet tee  134 . Therefore, when filling the cylinders solenoid valves  126  and  140  are open, solenoid valves  144  and  136  are closed, and vice versa. Dock box  98  also contains a pressure relief valve  152 , which is interposed between water line  138  and discharge  150  to prevent over pressuring the system when pumping water into the cylinders  22 . 
   While the invention has been described, disclosed, illustrated and shown in various terms or certain embodiments or modifications which it has assumed in practice, the scope of the invention is not intended to be, nor should it be deemed to be, limited thereby and such other modifications or embodiments as may be suggested by the teaching herein are particularly reserved especially as they fall within the breath and scope of the claims hereto appended.