Self-contained hydraulic thruster for vessel

[0001] This utility patent application is a Continuation-In-Part of pending U.S. utility application Ser. No. 12/806,274 filed Aug. 9, 2010 entitled Hydraulic Thruster for Vessel; which was a Continuation-In-Part of pending U.S. utility application Ser. No. 12/800,026 filed May 6, 2010 entitled Modular Hydraulic Thruster System for Vessel; which was a Continuation-In-Part of pending U.S. utility application Ser. No. 12/381,245 filed Mar. 10, 2009 now U.S. Pat. No. 7,883,384 entitled Self-Contained Hydraulic Thruster for Vessel; which was a Continuation-In-Part of U.S. utility application Ser. No. 11/999,531 filed Dec. 6, 2007 entitled Self-Contained Hydraulic Thruster for Vessel which issued as U.S. Pat. No. 7,654,875 on Feb. 2, 2010; which was based upon U.S. provisional patent application Ser. No. 60/903,400 filed Feb. 26, 2007 entitled Self-Contained Hydraulic Thruster for Vessel; and claims the benefit of the earlier filing date of these applications.

[0002] 1. Field of the Invention

[0003] This invention relates to vessel propulsion systems, and in particular to a self-contained hydraulic thruster for vessel.

[0004] 2. Background of the Invention

[0005] Marine thrusters typically mount on barges and flat boats, and are used as propulsion for these vessels. One type of marine thruster employs a prime mover such as a diesel engine driving a hydraulic pump, together known as a “power pack”, and the resultant pressurized hydraulic fluid may be employed to drive a propeller attached to a lower unit.

[0006] One major problem associated with marine thrusters has been that where a centrally located tiltable lower unit has been retracted and tilted backwards for storage, maintenance, cleaning, etc., the protruding upper end of the lower unit interferes with the helm and helm platform, and prevents full upward tilting of the retracted lower unit. This problem was solved by U.S. Pat. No. 7,654,875 granted to Williams, incorporated hereinto by reference, which provided lower units laterally offset from a base and helm platform, thus avoiding interference between the lower unit(s) and helm platform when tilting retracted lower unit(s) forward for storage or shipping.

[0007] However, there are still a number of problems associated with currently available marine thrusters. One problem is the absence of a strong, redundant tilt actuator system whose components are not immersed in water, thus reducing corrosion due to moisture.

[0008] Another challenge involves providing positive down-tilt stops which provide mechanical end-of-downwards-tilt travel stops, so that the lower unit is held securely vertical when tilted down, especially when developing thrust.

[0009] Still another problem is being able to provide means to position the marine thruster on a vessel deck without permanent downwards-protruding member(s), because such downwards-protruding member(s) interfere with storage and shipping by increasing the overall height of the unit.

[0010] Another problem with current designs is the lack of an effective extension and retraction mechanism for lower units which provides long extension/retraction travel. Long travel extension is especially important where the hydraulic thruster is to be installed on deep draft vessels.

[0011] It an object of this invention to provide a self-contained hydraulic thruster for vessel which provides a lower unit tilting means which is entirely above water level. Design features allowing this object to be achieved include a lower unit tiltably attached to a base, a housing arm attached to a housing and extending upwards from said housing, and a tilt actuator attached at one end to a distal end of the housing arm and at the other end to the base upper surface. Benefits associated with reaching this objective include reduction in moisture exposure to the tilt actuator, and associated cost savings in avoided oxidation damage and maintenance expense.

[0012] It is another object of this invention to provide a self-contained hydraulic thruster for vessel which provides positive down-tilt stops. Design features allowing this object to be achieved include a housing tiltably attached to a base at a pivot point, the pivot point being positioned at a front area of a housing wall such that a portion of the housing wall extends above a base upper surface when the housing is tilted completely down, a housing arm having a housing arm lower edge, each housing arm being attached to an aft area of its housing wall such that the housing arm lower edge rests on a base upper surface when the housing is tilted completely down. An additional down-tilt stop is provided by a down stop tab rigidly attached to a base lower unit cutout wall which extends into the lower unit cutout, so that when the housing is tilted completely down, a front edge of the housing wall butts against the down stop tab. Benefits associated with reaching this objective include more stable down-tilt stop function when the lower unit is in forward thrust, stronger and more solid lower unit installation, and increased ease of operation.

[0013] It is still another object of this invention to provide a self-contained hydraulic thruster for vessel incorporating provisions for accurately positioning the hydraulic thruster on the stern of a vessel to which it is to be attached. Design features allowing this object to be achieved include a pair of base bores through a base, and a pin corresponding to each base bore sized to slidably fit through a respective base bore which protrudes below the base to serve as a stop to a hydraulic thruster on a vessel stern, for subsequent permanent attachment, the pin being removable for storage or transportation of the hydraulic thruster. Benefits associated with reaching this objective include more accurate hydraulic thruster positioning, installation time savings, and the associated hydraulic thruster installation cost savings.

[0014] It is another object of the present invention to provide a self-contained hydraulic thruster for vessel whose lower unit(s) may be retracted and tilted up without interference from the helm platform. Design features allowing this object to be accomplished include at least one lower unit tiltably mounted to a base, laterally offset from a steering platform. Advantages associated with the accomplishment of this object include more efficient lower unit stowing for storage and/or transportation, greater tilt achievable (close to 90 degrees), the ability to tilt the propellers and lower unit completely out of the water for servicing and cleaning, decreased corrosion due to the ability of getting the lower units and propellers completely out of the water when not in use to reduce corrosion, and greater retraction of the lower unit.

[0015] It is another object of the present invention to provide a self-contained hydraulic thruster for vessel which allows long-travel extension and retraction. Design features allowing this object to be accomplished include a lower unit tiltably attached to a base, a cylinder through and extending downwards from a housing, a tube slidably and rotatably disposed within the cylinder, a ratio of a length of the cylinder to a length of the tube being substantially between 0.25 and 0.35, and long travel extension actuators whose lower end is attached at a lower end of the cylinder and whose upper end is attached to an extension collar encircling an upper end of the tube. Benefits associated with the accomplishment of this object include increased flexibility of installation on deep-hulled vessels, and flexibility of operation.

[0016] It is yet another object of this invention to provide a self-contained hydraulic thruster for vessel which is economical to build. Design features allowing this object to be achieved include the use of components made of readily available materials, and commercially available components such as an existing steering motor, overhung load adapter, hydraulic actuator, hydraulic power pack, hydraulic fluid reservoir, lower unit, propeller, steering gear, drive gear, and hydraulic lines. Benefits associated with reaching this objective include reduced cost, and hence increased availability.

[0028] FIG. 1 is an elevated left rear quarter isometric view of hydraulic thruster 20 mounted at vessel stern 4 of vessel 2. As may be observed in this drawing, hydraulic thruster 20 comprises hydraulic power pack 22 and helm platform 26 mounted atop base 30. Helm 24 and hydraulic fluid reservoir 28 are mounted on helm platform 26. Helm platform 26 is mounted some height above base 30, which aids the feeding of hydraulic fluid in hydraulic fluid reservoir 28 to hydraulic power pack 22.

[0029] Hydraulic power pack 22 is mounted at the front of base 30, while helm platform 26 is mounted at the rear of base 30. Helm 24 and hydraulic fluid reservoir 28 are mounted side-by-side atop helm platform 26.

[0030] Hydraulic thruster 20 comprises at least one lower unit 50 pivotally attached to base 30 at the rear edge of base 30. The embodiments depicted in FIGS. 1-3 depict two lower units 50 tiltably attached to base 30, one at the left rear of base 30, and the other at the right rear of base 30.

[0031] FIG. 2 is an elevated left rear quarter isometric view of hydraulic thruster 20, with its hydraulic power pack 22, helm 24, helm platform 26, and hydraulic fluid reservoir 28 removed, and depicting a steering actuator 34 and tie rod 36 steering system. FIG. 3 is an elevated left rear quarter isometric view of base 30 with lower units 50 removed, illustrating pins 40 being used to position base 30 on vessel 2 relative to vessel stern 4.

[0032] Each lower unit 50 comprises a cylinder 52 rigidly attached to a housing 70. In the preferred embodiment, housing 70 was rectangular in cross-section, and comprised housing roof 76, housing sides 78, and housing floor 80. A housing cylinder bore 72 was disposed in housing roof 76, and a housing cylinder bore 72 was disposed in housing floor 80. Each housing cylinder bore was sized to admit cylinder 52, which was disposed through housing cylinder bores 72, and immobilized therein, largely extending downwards from housing 70.

[0033] Cylinder 52 comprises cylinder bore 53 sized to slidably and rotatably admit tube 54. Propeller 56 is disposed at a lower end of tube 54, and when spinning provides thrust for hydraulic thruster 20. Tube 54 is slidably and rotatably disposed within cylinder 52. Steering function is achieved by rotating tube 54 and propeller 56 relative to cylinder 52 as indicated by arrow 86 in FIG. 1.

[0034] It may be noted that cylinder 52 extends through, and extends downwards from, housing 70. The axial length of cylinder 52 as compared to the axial length of tube 54 is significant, because a cylinder 52 of substantial length relative to the length of tube 54 permits long travel extension and retraction of tube 54, because a long cylinder 52 provides support for tube 54 during such extension and retraction. For example, it was determined experimentally that tubes having lengths of 12 feet, 10.5 feet, and 7⅓ feet, are adequately supported by corresponding cylinders having a length of 4 feet, 3 feet and 2 feet respectively. Thus, the optimum ratio of cylinder 52 length to tube 54 length is substantially between 25% and 35%.

[0035] In the embodiment hydraulic thruster 20 depicted in FIGS. 1-3, steering clamp 58 having steering clamp aperture 59 is disposed directly atop housing roof 76. Steering clamp aperture 59 is sized to slidably admit tube 54 when steering clamp 58 is loose. When steering clamp 58 is tightened, steering clamp 58 frictionally grips tube 54 within steering clamp aperture 59, and then tube 54 is not free to translate nor rotate relative to steering clamp 58.

[0036] When tube 54 is to be extended or retracted relative to housing 70 and steering clamp 58 as indicated by arrow 87 in FIG. 1, steering clamp 58 must be loosened to allow tube 54 to slide through steering clamp bore 59. When tube 54 is retracted or extended to an amount desired, steering clamp 58 is tightened, to permit the steering function when lower unit 50 is tilted down and tube 54 is extended downwards for thrusting, and to prevent uncommanded extension when tube 54 is retracted upwards relative to housing 70.

[0037] To aid in the steering function, tube 54 comprises tube key 62 extending radially outwards from the upper end of tube 54, and corresponding steering clamp keyway 64 in steering clamp aperture 59 sized to slidably admit tube key 62. When tube 54 is extended fully downwards relative to cylinder 52, tube key 62 slides into steering clamp keyway 64, thus further helping prevent tube 54 from rotating relative to steering clamp 58.

[0038] Steering clamp 58 further comprises steering clamp arm 60 extending radially outwards from an upper end of steering clamp 58. In the dual-lower unit embodiment depicted in FIGS. 1-3, tie rod 36 connects ends of steering clamp arms 60 opposite steering clamps 58, which are the distal ends of steering clamp arms 60. Steering actuator 34 is attached at one end to tie rod 36, and at an opposite end to a housing 70. In the preferred embodiment, steering actuator 34 was a hydraulic cylinder.

[0039] Base 30 comprises at least one base lower unit cutout 44 at its rear edge, sized to slidably admit housing 70. Each housing 70 is rotatably attached to base 30, and rotatably disposed within a corresponding base lower unit cutout 44.

[0040] Disposed immediately forward of each base lower unit cutout 44 is a base bore 38 extending through base 3. A pin 40 is provided associated with each base bore 38 which slidably fits into its respective base bore 38. A length of pin 40 exceeds a thickness of base 3, such that when pin 40 is inserted through base bore 38 as indicated by arrows 42 in FIG. 2, a substantial length of pin 40 protrudes through the bottom of base 3 to butt against vessel stern 4, as shown in FIGS. 3 and 6.

[0041] Once pins 40 are inserted through respective base bores 38 as indicated by arrows 42 in FIG. 2, base 30 is positioned on vessel 2 such that both pins 40 butt up against vessel stern 4 as depicted in FIGS. 3 and 6, thus accurately positioning hydraulic thruster 20 on vessel 2 at vessel stern 4. Base 3 may then be attached to vessel 2 by any appropriate means, such as welding, bolting, bolting to weld tabs, etc. Pins 40 may then be removed from their respective base bores 38 until further needed.

[0042] It is important to note that pins 40 are removed from base 3 as indicated by arrow 43 in FIG. 3, for shipping and storage of hydraulic unit 20, such as is depicted in FIG. 5. When pins 40 are removed, base 3 may rest flat upon flat surface 116 of a container, flatbed truck, rail car, warehouse floor, etc., where hydraulic thruster 20 is to be transported or stored.

[0043] Each lower unit 50 comprises at least one upright, parallel housing arm 74, each housing arm 74 being substantially parallel to tube 54 and cylinder 52, and extending upwards from housing roof 76 in a direction substantially parallel to housing roof 70.

[0044] Each lower unit 50 further comprise a pair of tilt actuators 32, which tilt lower unit 50 as indicated by arrow 88 in FIG. 1. One end of each tilt actuator 32 is attached to an end of a housing arm 74 opposite housing 70; the other end of each tilt actuator 32 is attached to base upper surface 31. Thus, tilt actuators 32 are not immersed in water, but rather are disposed entirely above base upper surface 31, which helps protect tilt actuators 32 from water-induced corrosion.

[0045] Lower units 50 are tiltably attached to base 30. Extension and retraction of tilt actuators 32 cause lower units 50 to tilt down and up relative to base 30. In the preferred embodiment, a pivot tab 84 extends upwards from base upper surface 31 on either side of base lower unit cutout 44. Each pivot tab 84 contains a pivot point 82 which is pivotally attached to a forward part of a respective housing side 78.

[0046] Pivot tabs 84 have the effect of elevating pivot point 82 (which is the point at which lower unit 50 is tiltably attached to base 30) above base upper surface 31, which facilitates rotation of housing 70 relative to base 30 by reducing the clearance required between the forward end of housing 70 and the forward end of the base lower unit cutout within which it resides.

[0047] Another function of elevation pivot points 82 above base 30 is to elevate housing roof 76 above base upper surface 31. In the preferred embodiment base upper surface 31 was disposed at substantially the mid-height of housing sides 78. This positioning of housing 70 allows housing arms 74 to be securely attached to respective housing sides 78 (e.g. by welding), yet also allows housing arm lower edge 75 to be disposed at approximately the mid-height of housing side 78. This positioning of housing arm 74 allows housing arm lower edge 75 to rest on base upper surface 31 when lower unit 50 is tilted completely down, thus providing one of the two types of positive down-tilt stop of the instant design. The other type of positive down-tilt stop incorporated into the instant design is down stop tab 46, depicted in FIGS. 3 and 4.

[0048] The other type of positive down-tilt stop incorporated into the instant design is down stop tab 46, depicted in FIGS. 3 and 4. A down stop tab 46 is attached to a respective base lower unit cutout wall 45, positioned so that the front edge of a respective housing wall 78 butts against the down stop tab 46 when lower unit 50 is tilted completely down. This configuration is depicted in FIG. 4.

[0049] In this disclosure, the “forward” area of any component of the instant invention refers to the area closest to the bow of a vessel 2 upon which hydraulic thruster 20 is mounted, while the “aft” area of any component of the instant invention refers to the area closest to the vessel stern 4 at which hydraulic thruster 20 is mounted. Expressed another way, because hydraulic power pack 22 is mounted at the forward end of base 30 and cylinders 52 are mounted at the aft end of base 30, the “forward” area of any component of the instant invention refers to the area closest to hydraulic power pack 22, while the “aft” area of any component of the instant invention refers to the area closest cylinders 52. Laterally offset means displaced sideways in a direction perpendicular to the forward/aft axis of hydraulic thruster 20.

[0050] FIG. 4 is a side view of self-contained hydraulic thruster 20 for vessel with its lower unit 50 tilted down by tilt actuators 32, and with its tube 54 retracted relative to its cylinder 52 by means of extension actuators 35. FIG. 5 is a side view of self-contained hydraulic thruster 20 for vessel with its lower unit 50 tilted up by tilt actuators 32, and with its tube 54 retracted relative to its cylinder 52 by means of extension actuators 35. FIG. 6 is a side cross-sectional view of self-contained hydraulic thruster 20 for vessel with its lower unit 50 tilted down by tilt actuators 32, and with its tube 54 extended relative to its cylinder 52 by means of extension actuators 35. FIGS. 4-6 also depict a steering motor 96 and tube gear 92 steering system, which is used in the single lower unit 50 hydraulic thruster depicted in FIG. 9.

[0051] As may be observed in these figures, lower unit 50 may include a pair of extension actuators 35 whereby tube 54 may be extended and retracted relative to cylinder 52. One end of extension actuator 35 is attached to a lower end of cylinder 52, and the other end of extension actuator 35 is attached to actuator collar 114.

[0052] Actuator collar 114 slidably encircles the upper end of cube 54, and its upper surface butts up against the lower surface of swivel union 100, which is attached to the upper end of tube 54.

[0053] When extension actuators 35 urge actuator collar 114 upwards relative to cylinder 52 in order to retract tube 54, actuator collar 114 pushes swivel union 100 upwards, and so also tube 54 en train with swivel union 100.

[0054] When extension actuators 35 retract, actuator collar 114 descends under the influence of gravity, and so also do swivel union 100 and the tube 54 to which it is attached, en train, also under the influence of gravity, thus extending tube 54.

[0055] In the preferred embodiment, two actuators 34 were installed on each lower unit 50, substantially diametrically opposed from each other relative to cylinder 52.

[0056] As noted above, one function of elevation pivot points 82 above base 30 is to elevate housing roof 76 above base upper surface 31, thus allowing housing arms 74 to be securely attached to respective housing sides 78 (e.g. by welding), yet allowing housing arm lower edge 75 to reside at the approximate mid-height of housing side 78. This positioning of housing arm 74 allows housing arm lower edge 75 to rest on base upper surface 31 when lower unit 50 is tilted completely down as depicted in FIG. 4, thus providing one of the two types of positive down-tilt stop of the instant design.

[0057] Because the instant design incorporates two housing arms 74, each attached to a respective housing side 78, and associated with each housing arm 74 is a housing arm lower edge 75, each disposed at the approximate mid-height of the housing side 78 to which it is attached, the instant pair of housing arms 74 associated with each lower unit 50 of the instant design provide two positive down-tilt stops to each lower unit 50, where each of the two associated housing arm lower edges 75 come into contact with, and rest upon, base upper surface 31 when the lower unit 50 is tilted completely down. This configuration is depicted in FIG. 4.

[0058] It can be readily appreciated that because each base lower unit cutout 44 incorporates two base lower unit cutout walls 45, up to two down stop tabs 46 may be mounted in each base lower unit cutout, one attached to each associated base lower unit cutout walls 45. In this situation, a total of four positive tilt down-stops are provided to each lower unit 50: two housing arm lower edges 75 firmly resting on base upper surface 31, and two down stop tabs 46 against which the forward edges of respective housing walls 78 butt against.

[0059] As may be noted in FIGS. 4-6, hydraulic thruster 20 may incorporate a steering motor 96 and tube gear 92 steering system. This system may be used where a single lower unit 50 is mounted to hydraulic thruster 20, as is depicted in FIG. 9, or in a dual lower unit 50 configuration. In this configuration, steering motor 96 is mounted to housing 70. Steering motor 96 drives steering motor gear 98, which in turn drives tube gear 92 and tube gear clamp 94, which then rotates the tube 54 to which tube gear clamp 94 is clamped. A dual lower unit 50 embodiment would incorporate a steering clamp arm 60 rigidly attached to each steering clamp 64, and tie rod 36 joining the distal ends of the steering clamp arms 60.

[0060] FIG. 5 also illustrates the instant hydraulic thruster 20 in the storage or transportation configuration. In this configuration, lower unit 50 is fully retracted and tilted up, and pins 40 are removed from base bores 38. Thus configured, hydraulic thruster sits flat on the flat surface 116 upon which it rests, be that surface a flat bed truck, container floor, warehouse, or other resting location. This compact storage/transportation configuration saves time and space when loading the instant hydraulic thruster into a container (it can simply be wheeled in on a float), truck, or other storage/transportation surface.

[0061] FIG. 7 is a front elevated view of a tube gear clamp 94, with its tube gear clamp first half 106 unattached from its tube gear clamp second half 108. FIG. 8 is a side elevated view of a tube gear clamp 94, with its tube gear clamp first half 106 attached to its tube gear clamp second half 108.

[0062] Tube 54 is sized to slidably fit into cylinder bore 53 in cylinder 52. Thus, tube 54 is free to rotate and reciprocate within cylinder 52. Referring now to FIG. 7, a front elevated view of tube gear clamp 94, with its tube gear clamp first half 106 unattached from its tube gear clamp second half 108; and FIG. 8, a side elevated view of tube gear clamp 94, with its tube gear clamp first half 106 attached to its tube gear clamp second half 108; we observe that reversible steering motor 96 drives steering motor gear 98, which in turn drives tube gear 92. Tube gear 92 is rigidly attached to tube gear clamp second half 108, and steering motor 96 is rigidly attached to housing 20. In the preferred embodiment, tube gear clamp second half 108 was attached to tube gear 92 with welds 93.

[0063] Tube gear clamp 94 contains tube gear clamp bore 107, which is sized to slidably admit tube 54. Tube gear clamp key 109 extends into tube gear clamp bore 107, and is sized to slidably reciprocate within tube keyway 73 in tube 54, as depicted in FIG. 4. Tube keyway 73 is disposed longitudinally on the outside surface of tube 54.

[0064] Tube gear clamp key 109 reciprocating within tube keyway 73 prevents tube 54 from rotating relative to tube gear clamp 94 and tube gear 92. Thus, when steering motor 96 turns tube gear 92 and rigidly attached tube gear clamp 94, tube 54 turns at the same rate, thereby providing a steering function to hydraulic thruster for vessel 20.

[0065] The top view shape of tube gear clamp first half 106 and tube gear second half 108 is substantially a 180 degree arc of a circle, with a tube gear clamp flange 112 on each end. When mounted to tube 54, tube gear clamp first half 106 and tube gear second half 108 are emplaced around tube 54 such that tube 54 is slidably disposed within tube gear clamp bore 107. Then a tube gear clamp first half 106 flange 112 is attached to a corresponding tube gear second half 108 flange 112 (using fasteners such as bolts, in the preferred embodiment), as depicted in FIG. 8.

[0066] Fasteners such as bolts or screws through both flanges 112 may be used to manually tighten (and loosen) tube gear clamp 94 on tube 54, or alternately, tube gear clamp actuator 110 may mounted to one of the two remaining unattached flanges 112, and its actuator attached to the other remaining unattached flanges 112, as depicted in FIG. 8. Tube gear clamp actuator 110 serves to loosen and tighten tube gear clamp 94 on tube 54. Tube gear clamp 94 must be loosened, or opened, prior to extending or retracting tube 54 within cylinder 52, and tube gear clamp actuator 110 permits the opening and closing of tube gear clamp 94 to be accomplished remotely.

[0067] Following extension or retraction of tube 54, tube gear clamp 94 must be closed or tightened, in order to help prevent tube 54 from rotating within tube gear clamp 94 while steering, and to lock tube 54 into position relative to cylinder 52 axially.

[0068] FIG. 9 is an elevated left rear quarter isometric views of a hydraulic thruster 20 embodiment having a single lower unit 50. Thus, the instant disclosure teaches both single and dual lower unit 50 embodiments of the instant hydraulic thruster 20. Both embodiments enjoy the benefits of a strong, redundant tilt actuator system whose components are not immersed in water, thus reducing corrosion due to moisture; two types of positive down-tilt stop; pins 40 through base bores 38 to position the hydraulic thruster 20 on a vessel stern 4 without permanent downwards-protruding member(s), and effective long extension/retraction travel extension actuators 35.

[0069] The steering actuator 34/steering clamp arm 60 steering system depicted in FIGS. 1-3 may be used with either the single lower unit 50 hydraulic thruster 20 embodiment, or the dual lower unit 50 hydraulic thruster 20 embodiment. The dual lower unit 50 hydraulic thruster 20 embodiment is illustrated in FIGS. 1-3; in the case of the single lower unit 50 hydraulic thruster 20 embodiment tie rod 36 would be omitted.

[0070] Similarly, the steering motor 96/steering motor gear 98/tube gear 92 steering system may be used with either the single lower unit 50 hydraulic thruster 20 embodiment, or the dual lower unit 50 hydraulic thruster 20 embodiment. The single lower unit 50 hydraulic thruster 20 embodiment is illustrated in FIG. 9; in the case of the dual lower unit 50 hydraulic thruster 20 embodiment tie rod 36 joining distal ends of steering clamp arms 60 would be included.

[0071] In the preferred embodiment, base 30, helm platform 26, helm 24, hydraulic fluid reservoir 28, housing 70, tube 54, cylinder 52, tube gear clamp 94, and tube gear were made using metal, synthetic, corrosion resistant metal, corrosion resistant metal fasteners, welded construction, or other appropriate materials and processes. Steering motor 96, steering motor gear 98, tube gear 92, steering actuator 34, tilt actuator 32, extension actuator 35, tube gear clamp actuator 110 and hydraulic power pack 22 were commercially available items. Steering actuator 34, tilt actuator 32, extension actuator 35, and tube gear clamp actuator 110 may be hydraulic actuators, electric linear motors, or any other appropriate actuators. Base 30 and base upper surface 31 were made of plates, C beams, I beams, or any other appropriate structural member shape.

[0072] While a preferred embodiment of the invention has been illustrated herein, it is to be understood that changes and variations may be made by those skilled in the art without departing from the spirit of the appending claims.

• [0073] 2 vessel
• [0074] 4 vessel stern
• [0075] 20 hydraulic thruster
• [0076] 22 hydraulic power pack
• [0077] 24 helm
• [0078] 26 helm platform
• [0079] 28 hydraulic fluid reservoir
• [0080] 30 base
• [0081] 31 base upper surface
• [0082] 32 tilt actuator
• [0083] 34 steering actuator
• [0084] 35 extension actuator
• [0085] 36 tie rod
• [0086] 38 base bore
• [0087] 40 pin
• [0088] 42 arrow
• [0089] 43 arrow
• [0090] 44 base lower unit cutout
• [0091] 45 base lower unit cutout wall
• [0092] 46 down stop tab
• [0093] 50 lower unit
• [0094] 52 cylinder
• [0095] 53 cylinder bore
• [0096] 54 tube
• [0097] 56 propeller
• [0098] 58 steering clamp
• [0099] 59 steering clamp aperture
• [0100] 60 steering clamp arm
• [0101] 62 tube key
• [0102] 64 steering clamp keyway
• [0103] 70 housing
• [0104] 72 housing cylinder bore
• [0105] 73 tube keyway
• [0106] 74 housing arm
• [0107] 75 housing arm lower edge
• [0108] 76 housing roof
• [0109] 78 housing side
• [0110] 80 housing floor
• [0111] 82 pivot point
• [0112] 84 pivot tab
• [0113] 86 arrow
• [0114] 87 arrow
• [0115] 88 arrow
• [0116] 92 tube gear
• [0117] 93 weld
• [0118] 94 tube gear clamp
• [0119] 96 steering motor
• [0120] 98 steering motor gear
• [0121] 100 swivel union
• [0122] 106 tube gear clamp first half
• [0123] 107 tube gear clamp bore
• [0124] 108 tube gear clamp second half
• [0125] 109 tube gear clamp key
• [0126] 110 tube gear clamp actuator
• [0127] 112 tube gear clamp flange
• [0128] 114 actuator collar
• [0129] 116 flat surface