METHODS AND DEVICES FOR PERSONAL WATER CRAFT

Abstract

Jet-powered water craft have become popular recreational pleasure craft for people worldwide as well as providing rapid response in a water environment for life savers, police, customs, etc. However, once the throttle has been cut there is no braking or steering mechanism for such craft. Equally such braking or steering is limited at low speeds. Accordingly it would be beneficial to provide means for braking and/or steering such jet-powered water craft under low speed operation and/or when the throttle is cut. According to embodiments of the invention such mechanisms are provided whilst providing for ease of use during operation as well as beaching/launching/storage.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims the benefit of U.S. Provisional Patent Application 61/471,764 filed Apr. 5, 2011 entitled “Methods and Devices for Personal Water Craft.”

FIELD OF THE INVENTION

This invention relates to personal water craft and more specifically to mechanisms for braking them and steering them at low speed.

BACKGROUND OF THE INVENTION

Jet-propelled water craft have become popular recreational/pleasure craft for a significant number of people across a wide age range through factors such as ease of use, stability, and safety from lack of blade type propulsion. This ease of use also stems from the fact that they are typically designed to be steered using exhaust fluid flow pressure developed from a movable jet nozzle submerged below the surface of the water. However, as the throttle-controlled thrust is retarded, the ability of the user to steer the water craft is substantially reduced or eliminated. Further, as most jet-propelled water craft have no rudders, any type of substantial reduction in exhaust pressure, coupled with a steering capability that depends upon a steerable exhaust nozzle, typically makes it impossible to steer such water craft effectively at anything than other than when the exhaust pressure is high.

However, when the user reduces the throttle or cuts the throttle, thereby reducing or cutting the exhaust pressure respectively, and is riding without any steering, the water craft is prone to cause accidents since the momentum of the water craft and its inertia caused by the thrust produced by the jet stream of water just prior to being cut will propel the craft in that given direction.

Within the prior art various mechanisms have been proposed to provide alternative steering capability for jet-propelled water craft. However, such mechanisms have shortcomings. For example, some rudder mechanisms require manual operation to deploy into the water, or to be removed from the water. Spring-biased rudder mechanisms, while providing the ability to displace upwardly upon contact with foreign objects, typically remain in the water at all times, producing excessive drag during high-speed operation of the water craft. As an example see FIGS. 4 and 5 that depicts the teachings of Adomeit in U.S. Pat. No. 6,878,020 entitled “Jet Boat Emergency Braking System” and Murray in U.S. Pat. No. 6,086,437 entitled “Blow Back Rudder for a Water Craft” respectively. Finally, some of these mechanisms are designed to deploy automatically, see for example Posti in U.S. Pat. No. 3,982,494 entitled “Auxiliary Rudder for a Jet Propulsion Unit”, and depicted in FIG. 1, wherein a piston controlled by water pressure to raise the rudder as speed increases is presented. However, at low speed and cut-throttle such rudders trail behind the behind the water craft with significant elements above the water line Thus, such devices present a significant safety hazard to anyone falling off of the water craft during use.

Other attempts to deal with the problem of providing slow speed steering control to jet-powered water craft in a safe and efficient manner include the use of a third class lever connected to a rudder, which pivots from the uppermost portion of the lever, where it is attached to the jet nozzle. Thus, the rudder extends behind the craft for some distance while deployed in the steering position, and extends both behind the craft and above the water line while in the stowed or “running” mode. Such operational characteristics present a significant hazard to any operator, or passenger of the water craft that falls to the rear of the craft during operation. Further, re-boarding of the craft after a fall is quite difficult if the rudder apparatus projects into the path of the boarding operator and/or passenger.

In an alternate approach Pereira in U.S. Pat. No. 5,970,898 entitled “Jet Ski” teaches to a foot activated braking paddle for a jet-propelled water craft. Unlike other approaches the braking paddle is deployed from the middle portion of the hull as evident in FIG. 2. Other examples of such approaches include Adomeit in U.S. Pat. No. 6,652,333 entitled “Jet Boat Steering System”, and Swartz in U.S. Pat. No. 6,443,785 entitled “Method and Apparatus for Self-Deployed Rudder Assembly.” Willis in U.S. Pat. No. 7,168,384 entitled “Personal Water Craft Braking Apparatus” provides a variant to the deployment of brakes into the exhaust nozzle flow to dig the stern of the water craft deeper into the water rather than simply re-directing the exhaust flow in other than the direction of motion of the water craft, as depicted in FIG. 3.

Generally the prior art approaches do not allow for adjustments in the level of thrust required to deploy and/or store the rudder based on the exhaust pressure developed at idle or low speeds being primarily focused to higher exhaust pressures, nor do such devices allow for raising the rudder completely out of the way for beaching/launching/storing the jet-powered water craft. Similarly the provision of operator activated brakes does not allow for the scenarios where the rider has been thrown off and the water craft is progressing forward under its own momentum.

Accordingly, it would be evident to one skilled in the field that there exists a requirement to be able to steer/brake a jet propelled water craft under circumstances that include but are not limited to when the throttle is cut and no thrust is being produced by the jet nozzle and when the throttle is operating and low thrust is being produced by the jet nozzle. It would be further beneficial for such mechanisms of steering/braking to be compatible with the beaching/launching/storing of the jet powered water craft as well as the users' ability to mount/dismount/use the jet-powered water craft.

SUMMARY OF THE INVENTION

It is an object of the present invention to address deficiencies in the prior art with respect to personal water craft and mechanisms for braking them and steering them at low speed.

In accordance with an embodiment of the invention there is provided a device comprising a hull forming a predetermined portion of a water craft and a first channel comprising a predetermined portion of the hull having disposed within at least one flap of a plurality of flaps, each flap comprising at least a first surface and being positionable between a first position and a second position wherein the flaps position between the first and second positions is determined in dependence upon the pressure applied by water impinging upon the first surface resulting from motion of the hull through the water.

In accordance with an embodiment of the invention there is provided a device comprising:

• a hull forming a predetermined portion of a water craft;
• a nozzle mounted in a predetermined location on the hull receiving water via a channel forming a predetermined portion of the hull and exhausting said water to provide variable thrust for the water craft between zero and a maximum thrust;
• a first flap comprising at least a plate and a mounting, the mounting for attaching the plate to the hull in a predetermined location and allowing the plate to pivotably displace between a first predetermined position and a second position wherein the plate is disposed at the first predetermined position when the thrust is zero, at a third position intermediate the first predetermined position and the second position when the thrust is the maximum thrust, and additional positions between the third and second positions in dependence upon the thrust of the nozzle and the velocity of the water craft.

In accordance with an embodiment of the invention there is provided a device comprising:

• an engine comprising at least a drive shaft and operating in dependence upon an engine control signal;
• a first coupling selectably engageable with a drive shaft of the engine and comprising a first impeller shaft;
• a first exhaust providing thrust to a water craft through the exhausting of water under pressure from the first exhaust, the pressure generated by a first impeller coupled to the first impeller shaft;
• a second coupling selectably engageable with another drive shaft and comprising a second impeller shaft;
• a second exhaust providing thrust to a water craft through the exhausting of water under pressure from the second exhaust, the pressure generated by a second impeller coupled to the second impeller shaft, wherein
• the first and second exhausts exhaust in opposite directions thereby allowing one of the first and second exhausts to provide driving thrust and the other of the first and second exhausts to provide braking thrust.

Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described, by way of example only, with reference to the attached Figures, wherein:

FIG. 1 depicts a prior art rudder according to Posti in U.S. Pat. No. 3,982,494;

FIG. 2 depicts a prior art brake according to Pereira in U.S. Pat. No. 5,970,898

FIG. 3 depicts a prior art brake according to Willis in U.S. Pat. No. 7,168,384;

FIG. 4 depicts a prior art rudder according to Adomeit in U.S. Pat. No. 6,878,020

FIG. 5 depicts a prior art rudder according to Murray in U.S. Pat. No. 6,086,437

FIG. 6 depicts a braking method according to an embodiment of the invention;

FIG. 7 depicts the braking method according to an embodiment of the invention under different scenarios.

FIG. 8 depicts a brake deployment mechanism according to an embodiment of the invention;

FIGS. 9A and 9B depict a brake deployment mechanisms according to an embodiment of the invention;

FIGS. 10 and 11 depict rudder/brake elements according to embodiments of the invention;

FIGS. 12 and 13 depict a rudder/brake mechanism according to an embodiment of the invention; and

FIG. 14 depicts a rudder/brake mechanism according to an embodiment of the invention.

DETAILED DESCRIPTION

The present invention is directed to personal water craft and more specifically to mechanisms for braking them and steering them at low speed.

Referring to FIG. 6 there is depicted a braking method according to an embodiment of the invention. As shown is a jet-powered water craft 600 from a rear elevational perspective showing the central body 610, the steering column 620, hull 630, and exhaust 680. Disposed into the hull 630 near the exhaust 680 are first channels 660 that have within them first brake flaps 670. Disposed to the outer edges of the hull 630 are second channels 640 with deployed within them second brake flaps 650. The operation of these first and second brake flaps 670 and 650 respectively is shown schematically in FIG. 7 by first and second cross-sections 700A and 700B respectively that are taken along the section X-X depicted in FIG. 6.

Referring to first cross-section 700A the jet-powered water craft is shown where the exhaust is non-operational or at low thrust (i.e. idling or low throttle). Accordingly the plurality of second brake flaps 650 within the second channel 640 are depicted as projecting forward such that any forward momentum results in the water being channeled into the regions between the second brake flaps 650 wherein it encounters the physical wall structure of second channel 640 thereby providing a braking effect. As the exhaust is increased and forward momentum increases the water pressure on the second brake flaps 650 increases thereby causing them to pivot about their mounting such that at higher exhaust/velocity they are deployed as depicted in second cross-section 700B. In this scenario the plurality of second brake flaps 650 are now acting to channel water flow increasingly towards the rear of the water craft thereby reducing the braking effect.

As would be evident to one skilled in the art this embodiment of the invention provides for breaking that is automatic as the position of the second brake flaps 650, and correspondingly first brake flaps 670 which are not shown for clarity, is dependent upon the velocity and characteristics of the brake flaps only. As such a reduction in forward momentum results in increased braking, leading to reduced velocity, increased braking etc. The brake flaps may be established in their default breaking position by a combination of mechanisms including for example springs, memory metals etc. In order to reduce fouling etc the spring mechanisms may be housed within the hull 630 of the jet-powered water craft. It would be evident that this approach allows easy storage/launching/beaching as nothing projects below the hull 630 or if it does the brake flaps will automatically pivot with any physical engagement to a beach/support etc. It would also be evident to one skilled in the art that predetermined sub-sets of the plurality of brake flaps within each channel may have different thresholds for transitioning thereby providing a different braking profile or that different channels may have different thresholds.

Now referring to FIG. 8 there is depicted an alternate method of deploying a physical structure for a jet-powered water craft. As shown a structure 800 comprises a plate 810 that can move between a first position 820 to a second position 830. The plate 810 is mounted via first, second, and third arms 840A to 840C respectively to mount 880 attached to the water craft body. The second and third arms 840B and 840C respectively being attached to slider 890 that slides within a groove 850 of the mount 880 whilst first arm 840A is pivotably mounted to one end of the mount 880. A spring, not shown for clarity, or other mechanism provides tension to keep the plate 810 in first position 820 when there is no pressure against the plate 810.

Increasing pressure against the plate 810 results in the first to third arms 840A to 840C respectively in combination with the fixed pivot and slider 850 providing a resultant motion 870 for the plate 810 between the first position 820 and second position 830 according to the pressure applied and the characteristics of the structure 800 including but not limited to friction of slider 850 in mount 880 and the tensional characteristics of spring. As such with increasing momentum and water velocity the pressure on plate 810 increases thereby translating the plate 810 towards the second position 830 wherein it provides reduced restriction to water flow and thereby reduced braking effect on the water craft.

Referring to FIG. 9A there is depicted a first deployment scenario 900 according to an embodiment of the invention wherein a first mechanism 920 is disposed to one side of the exhaust flow from an exhaust 910 and a second mechanism 930 is disposed to the other side of the exhaust flow. Initially at rest the plates are disposed in their first position and restrict the flow from the exhaust. Initially the increased exhaust flow pushes each of the plates within the first and second mechanisms to a position wherein they are outside the flow at some intermediate position between the first and second positions. Now as velocity increases for the jet-powered water craft water flow either side of the exhaust 910 increases thereby further increasing pressure on the plates such that as the velocity of the water-craft increases they continue to move to their second position with lowest resistance to water flow. Accordingly it would be evident that first deployment scenario provides for highest braking when the exhaust is zero/low and then provides intermediate braking as the velocity increases with the exhaust at full throttle (or close to it) and then continues to reduce the applied braking force as velocity of the jet-powered water craft increases. As such the braking characteristic is ongoing even once full throttle has been initially engaged as the craft begins to increase speed.

Now referring to FIG. 9B there is depicted a second deployment scenario 900B according to an embodiment of the invention wherein a first mechanism 940 is disposed to one side of a mounting plate 960 and a second mechanism 950 is disposed to the other side of the mounting plate 960 wherein these elements are laterally displaced from the exhaust flow provided by exhaust 910. Accordingly in this scenario the position of each plate is now determined solely by the water flow arising from the forward momentum of the jet-powered water craft rather than having any dependence upon the exhaust flow from the exhaust 910. As such increasing velocity of the jet-powered water craft results in the plates moving to their second position with reduced resistance. At low speed the plates are thereby deployed providing braking resistance to the jet-powered water craft.

It would be evident to one skilled in the art that the combination of first and second mechanisms 940 and 950 together with the mounting plate 960 may be deployed in secondary channels within the hull of the jet-powered water craft rather than directly adjacent to the exhaust 910. It would be further evident that providing a pair of these either side of the exhaust 910, wherein the mounting plates 960 are vertically disposed rudder elements coupled to the steering of the jet-powered water craft, provides for a rudder assembly that provides increased resistance/control at low velocity with reduced resistance control at high velocity wherein primary direction may be still therefore derived from the directional adjustment of the exhaust 910 for example.

It would be evident to one skilled in the art that the profile of the plate position (or angle relative to the water flow from the exhaust nozzle) with thrust may be varied according to a variety of factors including but not limited to the design of the water craft, a characteristic of a target user of the water craft such as novice, beginner, or expert, and legal requirements in the jurisdiction of use of the water craft. Optionally the braking structure such as provided by the first and second mechanisms may be attached to the nozzle such that the braking is determined primarily from the nozzle irrespective of direction of the nozzle as in some water craft the nozzle may be pivoted to change direction.

Referring to FIG. 10 there is depicted an element 1000 according to an embodiment of the invention that may form part of the plates within the first and second mechanisms 910 and 920 of FIG. 9A or 940 and 950 of FIG. 9B as well as the mounting plate 960 for example. As shown the element 1000 comprises a vertical plate 1020 that terminates at either distal end in distal plates 1010. Such a structure having been shown to provide improved steering performance, as a rudder, at low velocity versus a rudder comprising only vertical plate 1020. It would be evident that the distal plates 1010 may require additional structure in the hull to accommodate them as they move.

Referring to FIG. 11 there is depicted an element 1100 according to an embodiment of the invention for providing a plate as part of a rudder and/or brake assembly that has a variable resistance with velocity of the water craft. As shown the element 1100 comprises a central member 1110 with side panels 1120 disposed. Whilst central member 1110 may be formed from a rigid material the side panel 1120 is formed from a flexible material and is hollow being filled with a gas at a predetermined pressure. At low velocity the water pressure is insufficient to distort the outer surface of the central member and therefore the side panels 1120 provide a bulbous cross-section of the element 1100. At increased speed the water pressure on the side panel 1120 increases such that the gas within compresses and the profile of the panel 1120 reduces. If the side panels were used in combination with chambers within the central member 1110 then it is feasible to consider that at increased pressure the side panels 1120 flatten substantially resulting a narrow less bulbous profile for the element 1100. As such the efficiency of element 1100 as a rudder is directly related to the velocity of the jet-powered water craft such that its efficiency is highest at low velocities.

It would be evident to one skilled in the art that said chambers may be fitted with pressure valves such that gas flow between the side panels and chambers occurred as predetermined pressure thresholds were met.

Now referring to FIG. 12 there is depicted brake/rudder assembly according to an embodiment of the invention at rest in first cross-section 1200A and at speed in second cross-section 1200B. In first cross-section 1200A at rest (or low velocity) the brake/rudder assembly 1210 is deployed in a down ward direction providing the required steering capability as well as braking, as will be evident in reference to FIG. 13 wherein the concept is presented from a front-elevation perspective. As the velocity increases and pressure on the rubber/brake assembly 1210 increases it is deflected back and up into the hull of the jet-powered water craft and as evident in FIG. 13 forms a closed cover to the recess 1220 in the hull.

Accordingly referring to FIG. 13 first view 1300A corresponds to deployment of the rudder/brake assembly 1210 at zero or low velocity and second view 1300B corresponds to deployment at higher velocity as described in relation to second cross-section 1200B. Referring to first view 1300A there is shown the recess 1220 and brake/rudder assembly 1210 which comprises central member 1310, first side member 1320 and second side member 1330. As evident in FIG. 12 this deployment results in the brake/rudder assembly 1210 being substantially disposed as a conventional rudder below the jet-powered water craft but at the bow rather than the stern. Whilst steering from bow mounted rudders has reduced efficiency this is still a significant improvement compared to the absence of control/rudder from existing commercial jet-powered water craft when the exhaust is cut or reduced.

Now referring to second view 1300B at increased velocity the water pressure has pushed the brake/rudder assembly 1210 back which due to the pivot 1350 also results in it coming up against the hull and into the recess 1220 within the hull. Simultaneously the pressure on the first and second side members 1320 and 1330 respectively has resulted in them being pushed about their pivot mountings, not shown for clarity, such that they open, essentially like the front and back covers of a book with the central member 1310 as the spine of the book. In this manner they are pushed back, up, and out so that the overall result is they form a cover to the recess 1220 at increased velocity. It would be evident to one skilled in the art that the brake/rudder assembly 1210 may also be augmented with a manual mechanism to raise the brake/rudder assembly into position or lock it allowing eased storage/launching.

Within the embodiments of the invention described with respect to FIGS. 6 to 13 the control of the rudder/brake deployment has been driven through exploiting automatic physical aspects of the combination of weight, torsion, pressure etc in varying combinations. However, it would be evident to one skilled in the art that these mechanisms may be augmented with a system exploiting the engine of the jet-powered water craft or replaced in other scenarios.

Referring to FIG. 14 there are depicted first and second jet control scenarios 1400A and 1400B respectively. Considering first jet control scenario 1400A then there is depicted the conventional combination of engine 1410, exhaust 1420 and first coupling 1430 from the engine drive shaft to the shaft of the exhaust 1420 which is usually a waterproof coupling sealed at the wall of the hull as the drive must transition through from the inner air filled hull region to the water filled channel within which the exhaust 1420 operates. In this example first coupling 1430 is modified to couple/decouple the exhaust drive shaft from the engine drive shaft. Additionally a second coupling 1440 is shown that would be coupled to second exhaust 1450.

Considering initially the case of normal throttle operation as the jet-powered water craft is intended to move forward for the user then the exhaust 1420 is coupled to the engine 1410 and exhaust flow provides forward momentum. However, if the user now reduces or kills the throttle then the first coupling 1410 is decoupled and second coupling 1440 engaged such that the second exhaust 1450 operates thereby providing reverse thrust to act as a brake for the water craft.

Now referring to second jet control scenario 1400B the second exhaust 1450 has been replaced by first and second thrusters 1470 and 1480 which are coupled to the second coupler 1440 via third coupler 1460. According first and second thrusters 1470 and 1480 can provide braking thrust to the jet-powered water craft. However, it would also be evident that the proportion of thrust applied by each of the first and second thrusters 1470 and 1480 may be varied through operation of the third coupler 1460 and that this adjustment may be established in response to the users actions with the steering of the jet-powered water craft.

It would be apparent to one skilled in the art that first and second thrusters 1470 and 1480 may be directed to single exhausts each or multiple exhaust ports. It would also be apparent that the embodiments of the invention described with respect to FIGS. 6 through 14 may be used individually or in combination to provide different control configurations as well as different combinations of braking/steering.

The above-described embodiments of the present invention are intended to be examples only. Alterations, modifications and variations may be effected to the particular embodiments by those of skill in the art without departing from the scope of the invention, which is defined solely by the claims appended hereto.

Claims

1. A structure comprising:

a hull forming a predetermined portion of a water craft;

a first channel disposed within the hull; and

at least one flap of a first plurality of flaps disposed within the first channel, each flap comprising at least a first surface and being positionable between a first position and a second position wherein the flaps position between the first and second positions is determined in dependence upon the pressure applied by water impinging upon the first surface resulting from motion of the hull through the water.

2. The structure according to claim 1 wherein,

the first channel is disposed in the bow of the water craft; and

the at least one flap is disposed so as to cover the channel in the first position and expose the channel in the second position.

3. The structure according to claim 1 wherein,

the plurality of flaps automatically return to the first position when the pressure applied to the first surface is below a predetermined value.

4. The structure according to claim 1 further comprising;

a second channel disposed within the hull; and

at least one flap of a second plurality of flaps, each flap comprising at least a first surface and being positionable between a first position and a second position wherein the flaps position between the first and second positions is determined in dependence upon the pressure applied by water impinging upon the first surface resulting from motion of the hull through the water.

5. The structure according to claim 1 wherein,

the first position of the plurality of flaps is substantially perpendicular to the hull; and

the second position of the plurality of flaps is substantially parallel to the hull.

6. The structure according to claim 1 wherein;

the first position of the plurality of flaps is such that they are inclined in a manner that a first end of the flaps closer to the hull surface is further from the bow of the water craft than a second end of the flaps that are further from the hull surface.

7. The structure according to claim 1 wherein;

the plurality of flaps are associated with at least two flap groups of a plurality of flap groups, each flap group characterised by a predetermined flap profile defining a position of the flap ss as a function of water pressure.

8. A device comprising:

a nozzle mounted in a predetermined location on a hull of a water craft, the nozzle receiving water from a channel forming a predetermined portion of the hull and exhausting said water to provide variable thrust for the water craft between zero and a maximum thrust in dependence upon a control setting provided by a user of the water craft;

a first flap comprising at least a first plate and a first mounting, the first mounting for attaching the first plate to the hull in a predetermined location relative to the nozzle and being impinged upon by water during motion of the water craft and allowing the first plate to pivotably displace between a first predetermined position and a second predetermined position.

9. The device according to claim 8 wherein,

the predetermined location of the first flap is such that a predetermined portion of the water exiting the nozzle impinges upon the first flap; and

the position of the first flap varies between the first position and second position in dependence upon at least the thrust provided by the nozzle.

10. The device according to claim 8 wherein,

the predetermined location of the first flap is such that the water impinging on the first flap is not primarily from the nozzle; and

the position of the first flap varies between the first position and second position in dependence upon the velocity of the water craft.

11. The device according to claim 8 further comprising;

a second flap comprising at least a second plate and a second mounting, the second mounting for attaching the second plate to the hull in a predetermined location relative to the nozzle and being impinged upon by water during motion of the water craft and allowing the second plate to pivotably displace between a third predetermined position and a fourth position.

12. The device according to claim 11 wherein,

the first and second flaps are symmetrically disposed with respect to at least one of an axis of the nozzle and an axis of the water craft.

13. The device according to claim 11 wherein,

the first and second mountings are at least one of always in the nozzle exhaust and displaced laterally with respect to the nozzle exhaust.

14. The device according to claim 8 wherein,

the first plate comprises a base plate and a bladder, the bladder comprising a shell surrounding a chamber filled with a predetermined gas at a predetermined pressure such that the bladder presents a variable profile to the water in dependence upon the pressure exerted by water flowing past the bladder as a result of at least one of the nozzle water exhaust and motion of the water craft.

15. The device according to claim 14 wherein,

the base plate comprises at least a chamber of a plurality of chambers, each chamber linked to the bladder via a pressure valve such that gas movement between a chamber and the bladder was determined in dependence upon the pressure applied to the bladder by water impinging upon the bladder.

16. A device comprising:

an engine comprising at least a drive shaft and operating in dependence upon an engine control signal;

a first coupling selectably engageable with a drive shaft of the engine and comprising a first impeller shaft;

a first exhaust providing thrust to a water craft through the exhausting of water under pressure from the first exhaust, the pressure generated by a first impeller coupled to the first impeller shaft;

a second coupling selectably engageable with another drive shaft and comprising a second impeller shaft;

a second exhaust providing thrust to a water craft through the exhausting of water under pressure from the second exhaust, the pressure generated by a second impeller coupled to the second impeller shaft, wherein

the first and second exhausts exhaust in opposite directions thereby allowing one of the first and second exhausts to provide driving thrust and the other of the first and second exhausts to provide braking thrust.

17. The device according to claim 16 wherein;

the selective engagement of the first and second couplings are each controlled in dependence upon at least the throttle control signal.

18. The device according to claim 16 further comprising:

a third coupling selectably engageable with the another drive shaft and comprising a third impeller shaft;

a third exhaust providing thrust to a water craft through the exhausting of water under pressure from the third exhaust, the pressure generated by a third impeller coupled to the third impeller shaft; wherein

the principle axis of thrust of the second and third exhausts are disposed at approximately equal but opposite angles with respect to the principle axis of thrust of the first exhaust thereby allowing each of the second and third exhausts to selectively provide at least one of braking thrust and steering thrust to the water craft whilst the first exhaust selectively providing driving thrust to the water craft.

19. The device according to claim 18 wherein,

the first exhaust provides driving thrust in dependence upon at least a throttle control signal; and

the second and third exhausts provide at least one of braking thrust and steering thrust in dependence upon at least the throttle control signal and a steering control signal generated in dependence upon an aspect of the steering of the water craft.