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Title:
AN OUTBOARD PROPULSION UNIT POSITIONING ARRANGEMENT AND A DISPLACEMENT METHOD
Document Type and Number:
WIPO Patent Application WO/2017/202468
Kind Code:
A1
Abstract:
The present invention relates to an outboard propulsion unit positioning arrangement (30) for a marine vessel (10) adapted to be mounted on the transom (2) of the marine vessel(10), and a method for balancing the weight distribution and/or propulsion of a marine vessel (10). The outboard propulsion unit positioning arrangement (5) comprises at least a first and a second mounting portion (11, 12) for mounting a first and a second outboard propulsion unit (15, 16). The outboard propulsion unit positioning arrangement (5) comprises a displacement arrangement (20) adapted to translatory displace at least one of the first and the second mounting portions (11, 12) in a direction along the transverse axis (Ta) of the marine vessel (1). The arrangement and method provides for good trim capabilities of the marine vessel.

Inventors:
TUULIAINEN, Peter (Styrmansgatan 15, Köping, 731 41, SE)
Application Number:
EP2016/061903
Publication Date:
November 30, 2017
Filing Date:
May 26, 2016
Export Citation:
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Assignee:
VOLVO PENTA CORPORATION (., Göteborg, Göteborg, 405 08, SE)
International Classes:
B63H20/02
Attorney, Agent or Firm:
VOLVO TECHNOLOGY CORPORATION (Volvo Group Intellectual Property, BF14100 M1.7, Göteborg, 405 08, SE)
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Claims:
An outboard propulsion unit positioning arrangement (30) for a marine vessel (10) adapted to be mounted on the transom (2) of said marine vessel (1 ), said marine vessel having a vertical axis (Va), a transverse axis (Ta), and a longitudinal axis (La), said outboard propulsion unit positioning arrangement (5) comprising at least a first and a second mounting portion (1 1 , 12) for mounting a first and a second outboard propulsion unit (15, 16),

characterized in that

said outboard propulsion unit positioning arrangement (5) comprises a

displacement arrangement (20) adapted to translatory displace at least one of said first and said second mounting portions (1 1 , 12) in a direction along said transverse axis (Ta) of said marine vessel (1 ).

The arrangement according to claim 1 , wherein said translatory displacement is performed as a response to an input signal from an electronic control unit (30).

The arrangement according to any one of the preceding claims, wherein said first and said second mounting portions (1 1 , 12) is a first and a second bracket.

The arrangement according to any one of the preceding claims, wherein said translatory displacement of said first and said second mounting portions (1 1 , 12) are adapted to compensate for heel, or to achieve a selected inclination of said marine vessel (1 ).

The arrangement according to any one of the preceding claims, wherein said first and said second mounting portions (1 1 , 12) are arranged to at least one sliding rail (35, 35').

The arrangement according to claim 5, wherein said first mounting portion (32) is arranged on a first sliding rail (35) and said second mounting potion (33) is arranged on a second sliding rail.

7. The arrangement according to any one of claims 4-6, wherein said at least one sliding rail (10) is a straight sliding rail, an angled sliding rail, a curved sliding rail or combinations thereof.

The arrangement according to any one of the preceding claims, wherein said first and/or said second mounting portion (1 1 , 12) is adapted to carry one or more outboard propulsion units (15, 16), such as two or more.

The arrangement according to any one of the preceding claims, wherein said arrangement is adapted to mount three or more outboard propulsion units (15, 16).

10. The arrangement according to claim 9, wherein one of said three or more outboard propulsion units (15, 16) is fixed with respect to said translatory displacement.

1 1 . The arrangement according to any one of the preceding claims, wherein said first and said second mounting portions (32, 33) are adapted to be displaced synchronously in the same direction.

12. The arrangement according to any one of the preceding claims, wherein said

arrangement comprises an electronic control unit (30) and at least one sensor, such as one or more fuel & engine gauges, water gauges, gyros, speedometers, GPS devices, accelerometers, propulsion unit angle sensors, outboard propulsion position sensors or the like.

13. The arrangement according to claim 12, wherein at least one sensor is a gyro, and in that the displacement of said first and said second mounting portions (15, 16) are made in response to a signal from said gyro in order to change a weight distribution or to balance the marine vessel during a turn.

14. The arrangement according to claim 12 or 13, wherein at least one sensor is a speedometer, and in that said translatory displacement of said first and said second mounting portions (1 1 , 12) is permitted only when a value of said speedometer is below a threshold value.

15. The arrangement according to any one of the preceding claims, wherein at least said first and said second mounting portions (1 1 , 12) can be translatory displaced to a mooring position, wherein in said mooring position, the distance between said first and said second mounting portions (1 1 , 12) is substantially maximized or minimized.

16. The arrangement according to any one of the preceding claims, wherein said displacement arrangement comprises a hydraulic actuator, pneumatic actuator, electronic actuator, rotatable threaded shaft, or gear rack arrangement to displace at least said first and said second mounting portions (1 1 , 12).

17. The arrangement according to any one of the preceding claims, wherein said displacement arrangement comprises at least one mounting portion position indicator.

18. The arrangement according to any one of the preceding claims, wherein at least a first and a second outboard propulsion units (15, 16) are arranged on said first and second mounting portions (1 1 , 12) respectively.

19. The arrangement according to any one of the preceding claims, wherein said first and said second mounting portions (1 1 , 12) each are arranged with a vertical displacement mechanism and/or a tilt mechanism.

20. A marine vessel (1 ) comprising an outboard propulsion unit positioning

arrangement (5) according to any one of the preceding claims, and at least a first and a second outboard propulsion units (15, 16).

21 . The marine vessel according to claim 20, wherein said outboard propulsion unit positioning arrangement (5) is arranged on the transom (2) of said marine vessel (1 )-

22. The marine vessel according to claim 20 or 21 , wherein said outboard propulsion unit positioning arrangement (5) is arranged so that said translatory displacement is substantially parallel with or collinear to said transverse axis (Ta) of said marine vessel (1 ), or substantially follows the shape of the hull of said marine vessel (1 ).

23. The marine vessel according to any one of the claims 20-22, wherein said at least first and said second outboard propulsion units (15, 16) can be pivoted in order to steer said marine vessel in a sideways direction.

24. A method for balancing the weight distribution and/or propulsion of a marine

vessel (1 ), said marine vessel comprising an outboard propulsion unit positioning arrangement according to anyone of the preceding claims, and at least a first and a second outboard propulsion unit (15, 16), said marine vessel having a vertical axis (Va), a transverse axis (Ta), and a longitudinal axis (La),

characterized in that

said method comprises;

displacing at least one of said first and said second outboard propulsion units (15, 16) with a translatory displacement in a direction along said transverse axis (Ta).

25. The method according to claim 24, whereby said translatory displacement of said first and said second outboard propulsion units (15, 16) are towards each other, or away from each other.

26. The method according to claim 24, whereby said translatory displacement of said first and said second outboard propulsion units (15, 16) are displaced in the same direction, preferably synchronously.

27. The method according to claim any one of the claims 24-26, whereby said

translatory displacement is made as response to an input signal from an electronic control unit (30).

Description:
An outboard propulsion unit positioning arrangement and a displacement method

TECHNICAL FIELD

The invention relates to an outboard propulsion unit positioning arrangement and a method for balancing the weight distribution and/or propulsion of a marine vessel. The invention can be applied in marine vessels such as cargo ships, transport ships, passenger ferries, barges, leisure boats such as mono hulls, catamarans, trimarans, rigid hull inflatable boats (RIB), Walk arounds, day cruisers, houseboats and the like.

BACKGROUND

A lot of time and effort are put into making the boats go faster while at the same time reducing the weight to maximize performance. The hull is developed to reduce draft and resistance through water. To tweak the boats performance further, the outboard engines are constantly in focus to reduce the fuel consumption while increasing the power output. To improve a boats performance, multiple outboard engines can be mounted on the transom of the boat. Little effort is however put into manoeuvring boats especially at low speed.

The US patent application no. US 2002/0086594 A1 disclose an adjustable length bar for controlling the direction of thrust by two outboard engines. A boat having two outboard engines arranged with the adjustable bar is also disclosed. The adjustable bar may be configured to be extended or retracted. In a first state, the twin outboard engines may be set in a cruising mode with two parallel thrusts formed from the two outboard engines. In a second mode the two outboard engines may be set in a manoeuvring mode with the two outboard engines slightly rotated to form intersecting thrust directions forming a V. The V formed thrust direction is said to improve the manoeuvring properties of the boat. The two outboard engines are positioned at fixed positions.

To balance a boat when driving, the outboard engines and the boat may be trimmed. By balancing the boat fore and aft, the fuel consumption and the speed may be improved. Generally two systems are at play; a trim/tilt system and a trim tab actuator system.

Firstly; the trim/tilt system is configured to tilt the outboard engines to a desired angle with respect to the pivot axis and the hull. Secondly; the trim/tab actuator system is formed by two pivotable plates positioned flush with the underside of the hull. By manipulating the two systems, the boat may easier be on plane and speed increases as fuel consumption is reduced.

Balancing the boats become more and more important and it appears that there is a need for finding an arrangement which permits the balancing of the boat while providing good manoeuvring capabilities, even at low speed.

SUMMARY

The inventors have now found an arrangement which may be used for improving the manoeuvring of a marine vessel, especially at low speed. The arrangement may further be used for trimming the marine vessel when driving.

An object of the invention is to provide an outboard propulsion unit positioning

arrangement for a marine vessel and a method balancing the weight distribution of a marine vessel. The object is at least partly achieved by an arrangement according to claim 1 and a method according to claim 24. It is further an object to at least reduce the drawbacks of the prior art or to provide a useful alternative thereto.

The objects are at least partly solved by an outboard propulsion unit positioning arrangement for a marine vessel adapted to be mounted on the transom of the marine vessel. The marine vessel has a vertical axis, a transverse axis and a longitudinal axis.

The outboard propulsion unit positioning arrangement comprises at least a first and a second mounting portion for mounting a first and a second outboard propulsion unit.

The outboard propulsion unit positioning arrangement comprises a displacement arrangement adapted to translatory displace at least one of the first and the second mounting portions in a direction along the transverse axis of the marine vessel.

By the provision of the arrangement and the method disclosed herein improvements in the maneuverability of the marine vessel is provided. Low speed maneuvering such as docking procedure may be improved for example. The arrangement further enables a marine vessel to be balanced by shifting the weight distribution. The arrangement is preferably configured to permit balancing when driving as a trim or as a temporary response to a detected parameter such as the roll angle of the marine vessel. Heeling of the boat may thus be prevented or at least reduced and it might be possible to remove the trim plans on some marine vessels. It permits individual translatory displacement of a first and a second propulsion unit, independently of each other.

When driving, even at low speeds, and turning sharply, the marine vessel will want to roll about its longitudinal axis as a consequence of the centrifugal force the marine vessel is subjected to. The arrangement may be very useful to counteract the roll forces. This may be especially advantageous during a sharp turn to avoid a collision, i.e. an emergency turn. It has further been found that the arrangement may be useful during docking procedures, and especially when the marine vessel is operated via a single driver interface such as a joystick. The arrangement is thus useful for sideway displacement of the marine vessel. By enable a translatory displacement along the transverse axis of the propulsion units, the outboard propulsion units may be positioned as far away from each other as possible and thus provide good thrust and leverage on the marine vessel. According to an aspect, the translatory displacement may be performed as a response to an input signal from an electronic control unit. The input signal from the electronic control unit may be a signal derived from; a manual steering device, an automated steering device, a gyro, a throttle, an accelerometer, a speedometer, a fuel gauge, a water gauge, a GPS device, or combinations thereof. The arrangement may be steered as a response to different prevailing conditions on the marine vessel. This provides versatility. Just as matter of example, a prevailing condition could be the inclination of the marine vessel.

The first and the second mounting portions may be shaped in different ways. The first and the second mounting portions may be a first and a second bracket for example. The first and the second outboard propulsion unit mounted on the first and the second brackets may thus be translatory displaceable. It should be noted that according to an embodiment, the mounting portions may be formed by a portion of the outboard propulsion units.

According to an aspect, the translatory displacement of the first and the second mounting portions may be adapted to compensate for heel, or to achieve a selected inclination of the marine vessel. Just as a matter of example, the marine vessel may be temporarily subjected to a change of the weight distribution due to an excessive amount of people sitting at the port side of the marine vessel. The first and the second mounting portions, and thus the first and the second outboard propulsion units may be displaced to counteract the heel. The counteracting of the marine vessels heel may be done when the marine vessel in harbour or when driving.

According to an aspect, the first and the second mounting portions are arranged to at least one sliding rail. Each guiding rail operate as a guiding member to the first and the second mounting portion and a predetermined track along which the translatory displacement may be made and thus provides an arrangement which may be adapted to specific marine vessels and specific needs. The sliding rail may be formed by one continuous sliding rail or by two separate sliding rails. The first mounting potion may be provided on a first sliding rail, and the second mounting portion may be provided on a second sliding rail. This provides versatility to the displacement arrangement. Each mounting portion may further be operative on one or more sliding rails. Just as a matter of example, each mounting portion may be operable on two sliding rails enabling the mounting portion to be translatory displaced along different tracks.

The at least one sliding rail may be a straight sliding rail, an angled sliding rail, a curved sliding rail or combinations thereof. This enables flexibility in the direction of the translatory displacement may be performed. The first and/or the second mounting portion may be adapted to carry one or more outboard propulsion units, such as two or more. If a marine vessel comprises four outboard propulsion units, it may be advantageous to translatory displace the outboard propulsion units in pairs. The arrangement may be adapted to mount three or more outboard propulsion units. It is possible to provide a displacement arrangement comprising two or more mounting portions such as three, four, five, six or more mounting portions. However, it is also possible to provide two mounting portions while having at least three outboard propulsion units. In such an arrangement, the third outboard propulsion unit may be fixedly mounted to the marine vessel and thus fixed from translatory displacement.

One of the three or more outboard propulsion units may be fixed with respect to the translatory displacement. By having both fixed outboard propulsion units and translatory displaceable outboard propulsion units, it may be possible to provide marine vessels having three or more outboard propulsion units with a cheaper alternative than mounting all the outboard propulsion units on translatory displaceable mounting portions.

According to an aspect, the first and the second mounting portions are adapted to be displaced synchronously in the same direction. If having three or more mounting portions, two of the three or more mounting portions may be adapted to be displaced

synchronously in the same direction. This enables a fast displacement of multiple outboard propulsion units. The arrangement may comprise an electronic control unit and at least one sensor. The at least one sensor may be one or more of a fuel & engine gauges, water gauges, gyros, speedometers, GPS devices, accelerometers, propulsion unit angle sensors, outboard propulsion position sensors or the like. This provides a responsive arrangement which can be adapted to compensate or to trim a marine vessel and different prevailing conditions of the a marine vessel.

According to an aspect, the at least one sensor may be a gyro. The displacement of the first and the second mounting portions may thus be made in response to a signal from the gyro in order to e.g. change a weight distribution or the balance the marine vessel during a turn.

According to an aspect, the displacement of the mounting portions may be temporarily prevented. Just as a matter of example, provided with a sensor, the at least one sensor may be a speedometer. The translatory displacement of the first and the second mounting portions may be permitted only when a value of the speedometer is below a threshold value. It has been found that it may be advantageous to prevent displacement of the mounting portions in high speed. However, in some occasions it may be advantageous to permit displacement even at high speed. Such occasion may be to trim position of the propulsion units, especially during a turn when performing so called Ackermann steering.

It may be advantageous if the first and the second mounting portions cannot be displaced faster than a predetermined velocity when the marine vessel travels faster than a predetermined velocity. Just as a matter of example, if the marine vessel travels over 30 knots, the first and the second mounting portions should be restricted from being displaced at its maximum displacement velocity. This will impart a slower and more controlled balancing of the marine vessel during high speed.

According to an aspect, the first and the second mounting portions may be translatory displaced to a mooring position. In the mooring position, the distance between the first and the second mounting portions may be substantially maximized or minimized. If the distance is maximised, it provides for advantageous thrust positions especially for performing sharp turns, or sideway displacement. According to an aspect, the displacement arrangement may comprises a hydraulic actuator, pneumatic actuator, electronic actuator, rotatable threaded shaft, or gear rack arrangement to displace at least the first and the second mounting portions. The mounting portions may be displaced in different manners and it may be advantageous to adapt the specific mechanism behind the displacement to specific marine vessels. Hence this provides versatility to the arrangement in terms of that it is compatible with different types of displacement mechanism.

The displacement arrangement may comprise at least one mounting portion position indicator. This will provide relevant information to the driver and to the ECU e.g. an ECU of the marine vessel.

According to an aspect, the outboard propulsion unit positioning arrangement comprises at least a first and a second outboard propulsion unit. At least a first and a second outboard propulsion unit may be arranged on the first and second mounting portions respectively. The first and the second mounting portions may be an integrated portion on the outboard propulsion unit or the outboard propulsion units may be arranged on the mounting portions via standard attachment arrangements.

According to an aspect, the first and the second mounting portions may each be arranged with a vertical displacement mechanism and/or a tilt mechanism. This will enable the outboard propulsion units to be raised form the water or trim in a traditional manner for example.

According to an aspect, a marine vessel comprising an outboard propulsion unit positioning arrangement is also disclosed herein, and at least a first and a second outboard propulsion unit. The outboard propulsion unit positioning arrangement may be arranged on the transom of the marine vessel.

According to an aspect, the outboard propulsion unit positioning arrangement is arranged so that the translatory displacement is substantially parallel with or collinear to the transverse axis of the marine vessel, or substantially follows the shape of the hull of the marine vessel. When following the shape of the hull, it is meant that it follows the main form of the hull when viewed towards the transom, as illustrated by some of the figures herein. This enables a marine vessel with good trim and balancing capabilities.

At least first and the second outboard propulsion units can be pivoted in order to steer the marine vessel in a sideways direction. It has been found that the arrangement is advantageous when used for sideway displacements of the marine vessel. Hence marine vessels having the capability to position the outboard propulsion units enabling a sideway displacement, preferably cooperating with a bow thruster, is especially advantageous.

At least one object is at least partly met by a method for balancing the weight distribution and/or propulsion of a marine vessel. The marine vessel comprises an outboard propulsion unit positioning arrangement and at least a first and a second outboard propulsion unit. The marine vessel has a vertical axis, a transverse axis, and a

longitudinal axis. The method comprises displacing at least one of the first and the second outboard propulsion units with a translatory displacement in a direction along the transverse axis. By the provision of the method disclosed herein improvements in the maneuverability of a marine vessel is provided. Low speed maneuvering such as docking procedure may be improved for example. The arrangement further enables a marine vessel to be balanced by shifting the weight distribution and/or balancing the propulsion of the marine vessel. The arrangement is preferably configured to permit balancing when driving as a trim or as a temporary response to a detected parameter such as the roll angle of the marine vessel. Heeling of the boat may thus be prevented or at least reduced and it might be possible to remove the trim plans on some marine vessels. It permits individual translatory

displacement of a first and a second propulsion unit, independently of each other. The translatory displacement of the first and the second outboard propulsion units may be made towards each other, or away from each other, optionally in the same direction, preferably synchronously. The translatory displacement may be made as response to an input signal from an electronic control unit.

The invention can be applied in marine vessels such as cargo ships, transport ships, passenger ferries, barges, leisure boats such as mono hulls, catamarans, trimarans, rigid hull inflatable boats (RIB), Walk arounds, day cruisers, houseboats and the like.

Further advantages and advantageous features of the invention are disclosed in the following description and in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

With reference to the appended drawings, below follows a more detailed description of embodiments of the invention cited as examples.

In the drawings:

Fig. 1 shows a schematic overview of a marine vessel and its steering and propulsion arrangement for operating the marine vessel.

Fig. 2-5 show the marine vessel with a view towards the transom of the marine vessel and with the outboard propulsion units at different positions.

Fig. 6 shows the marine vessel with a view from above and with the outboard propulsion units at different positions.

Fig. 7a- 7d shows different configurations of displacement mechanisms illustrated using sliding rails in different configurations.

Fig. 8 shows a schematic block diagram of a method for balancing the weight distribution of a marine vessel.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

Figure 1 shows a schematic overview of a marine vessel 10 and a steering and propulsion arrangement 20 for operating the marine vessel 10. The steering and propulsion arrangement 20 comprises a helm station 21 . The helm station 21 is provided with a joystick 22, a steering wheel 23, throttles 24 and instrument and navigational data interface 25. The joystick 22 represents a single driver interface. A single driver interface enables a driver of the marine vessel to operate the steering and the propulsion of the marine vessel in a desired direction using only one single driver interface. A joystick is an example of such single driver interface. Another example is a touch pad interface representing a virtual joystick. A steering and thruster control module 26 operates as an integrating hub between the devices of the marine vessel 10 and specifically between the helm station 21 and the outboard propulsion units of the marine vessel 10. A navigation unit 27 such as an electronic compass and GPS device provides navigational data. The navigation unit may further operate as an autopilot. The steering and propulsion arrangement 20 can further comprises a bow thruster 28 positioned in the bow of the marine vessel 10. A bow thruster is located forward of the midship of the marine vessel, preferably in the proximity of the bow. The steering and thruster control module 26 may comprise sensors or be communicating with one or more sensors of the marine vessel such as gyros, speedometers, fuel & engine gauges, water gauges, GPS devices, accelerometers, propulsion unit angle sensors, or the like.

The marine vessel 10 comprises a first and a second outboard propulsion unit 40, 41 arranged on the transom 1 1 of the marine vessel 10. The first and the second outboard propulsion units 40, 41 are controlled via the helm station 21 , e.g. via the joystick 22, the steering wheel 23 and/or the throttle 24. The outboard propulsion units 40, 41 may be electrical motors, internal combustion engines (ICE) such as gasoline or diesel powered engines, or electrical and ICE hybrid propulsion unit. The first and the second outboard propulsion units 40, 41 are also referred to as port outboard propulsion unit 40 and starboard outboard propulsion unit 41 . An outboard propulsion unit positioning

arrangement 30 is operatively connected to the first and the second outboard propulsion units 40, 41 and arranged to enable a translatory displacement of the first and the second outboard propulsion units 40, 41 . It should be noted that the marine vessel 10 may be provided with two or more outboard propulsion units, such as three four or more. The outboard propulsion unit positioning arrangement 30 may thus be arranged to operate two or more outboard propulsion units, at least three, or at least four outboard propulsion units. This option to displace the propulsion units on the marine vessel in a translatory motion is available when the marine vessel is stationary or during motion, e.g. to prevent inclination. The weight distribution can thus be controlled e.g. in turns to counteract the inclination of the boat. Further, the yaw leverage which the thrust will impart on the marine vessel may be controlled without adjusting the throttle or even the steering of the specific propulsion unit. This provides additional trim capabilities.

For the purpose of orientation, the marine vessel 10 has a length extending along a longitudinal axis La, a width extending along a transverse axis Ta, and a height extending along a vertical axis Va.

Figure 2 shows the marine vessel 10 of figure 1 with a view towards the transom 1 1 and the first and the second outboard propulsion units 40, 41 . Figure 2 further shows the outboard propulsion unit positioning arrangement 30, a schematic illustration of the steering and thruster control module 26. The outboard propulsion unit positioning arrangement 30 comprises a displacement arrangement 31 adapted to translatory displace the first and the second outboard propulsion units 40, 41 . The translatory displacement is illustrated by the arrows in figure 2. The outboard propulsion unit positioning arrangement 30 comprises a first and a second mounting portion 32, 33 on which the first and the second outboard propulsion units 40, 41 are respectively arranged.

The displacement arrangement 31 is adapted to displace the first and the second mounting portions 32, 33 so as to effectuate a displacement of the first and the second outboard propulsion units 40, 41 in a transverse direction, i.e. in a direction along the transverse axis Ta of the marine vessel 10. The displacement is effectuated as a response to an input signal from the steering and thruster control module 26 operating as an electronic control unit ECU. As can be gleaned, by displacing the first and the second outboard propulsion units 40, 41 , the weight distribution and thus the point of balance of the marine vessel 10 may be moved. Just as a matter of example, it may be

advantageous to move the point of balance when driving the marine vessel 10 e.g. to trim the marine vessel or to compensate for persons sitting on the side of the marine vessel 10. It may also be advantageous to displace the first and the second outboard propulsion units 40, 41 during a docking scenario. It may further be advantageous to displace the first and the second outboard propulsion units 40, 41 after the marine vessel has docked.

The outboard propulsion unit positioning arrangement 30 may be configured in different ways. It is important however that the outboard propulsion unit positioning arrangement 30 enables the displacement of both the first and the second mounting portions 32, 33 so that the first and the second outboard propulsion units 40, 41 may be displaced. The outboard propulsion unit positioning arrangement 30 in figures 2-5 comprises a sliding rail 35 along which the first and the second mounting portions 32, 33 may slide. As an option, instead of having two or more outboard propulsion units sharing one sliding rail, each outboard propulsion unit may be mounted on its own sliding rail, i.e. its own displacement mechanism.

The sliding rail 35 is positioned on the transom 1 1 of the marine vessel 10, and extends in a transverse direction along the transverse axis Ta across the transom 1 1 . The sliding rail 35 extends a length Le across the transom 1 1 . The length Le of the sliding rail in the transverse direction is in the shown embodiment approximately 90 % of the width of the transom 1 1 . As can be seen in figure 2, the slide rail 35 is arranged slightly above the water line of the marine vessel, indicated in figure 2 by a still water line Sw. The displacement arrangement 31 may also be configured in different ways. The displacement arrangement 31 is in figure 2 formed by a first and a second hydraulic piston which may be operated so as to displace the first and the second mounting portions 32, 33 and thus the first and the second outboard propulsion units 40, 41 . For illustrative purposes the first and the second hydraulic piston is shown as being mounted on the transom as well, but may as an option be mounted inside of the hull of the marine vessel 10 and act on the first and the second mounting portions 32, 33 through a slot in the hull if desirable. Other suitable mechanism to displace the first and the second mounting portions 32, 33 are pneumatic pistons, electric actuators, gear racks, rotatable treaded shafts, chain- or wire mechanisms, just to mention a few. Mounting portion and/or outboard propulsion units position indicators may of course be provided.

Figure 3 shows the marine vessel of figure 2 but with a load L applied on the port side of the marine vessel 10. The load L is only for illustrative purposes and representative of any load which may temporarily heel the marine vessel 10, i.e. changing the weight distribution or the marine vessel may be subjected to a wave which heels the boat. A gyro continuously forwards the roll angle of the marine vessel to the steering and thruster control module 26. The steering and thruster control module 26 detect a deviation of the roll angle of the marine vessel 10 and compensates for the deviation by displacing the first and the second outboard propulsion units 40, 41 to starboard as indicated by the arrows above the first and the second outboard propulsion units 40, 41 . The displacement is made until the roll angle is indicating an acceptable roll angle, or a set roll angle. Figure 4 shows the marine vessel 10 after the displacement of the first and the second outboard propulsion units 40, 41 . As can be noticed, the marine vessel 10 is again horizontal, i.e. parallel with the still water line Sw. Figure 4 indicates with dashed lines the earlier positions of the first and the second outboard propulsion units 40, 41 . When the applied load L ceases, the first and the second outboard propulsion units 40, 41 may be displaced back to their original, or earlier, positions, in figure 4 indicated by the dashed lines.

As can be gleaned from the above, the first and the second outboard propulsion units 40, 41 may be displaced back and forth as response to an input signal from the steering and thruster control module 26, or any other suitable ECU. Figure 5 shows the marine vessel 10 but with the first and the second outboard propulsion units 40, 41 displaced to the ends of the sliding rail 35. The first and the second outboard propulsion units 40, 41 are as far away from each other as possible. The driver has in the shown embodiment given a mooring command, or docking command, via the helm station of the marine vessel 10. To enable good thrust leverage it is advantageous if the first and the second outboard propulsion units 40, 41 are as far away from each other as possible. This will provide better joystick steering conditions for example. In order for a sideway displacement of the marine vessel 10, the first and the second outboard propulsion units 40, 41 are rotated e.g. 90 5 port or starboard dependent on the desired direction of displacement. By using the bow thruster and the first and the second outboard propulsion units 40, 41 the marine vessel 10 may thereafter be displaced in a straight starboard or a straight port direction if desirable. Figure 6 shows the marine vessel 10 with a view from above. Figure 6 further shows the first and the second propulsion units 32, 33. As mentioned above, the mounting portion may be translatory displaced in order to translatory displace at least one of the first and the second propulsion units 32, 33. Figure 6 illustrates the scenario in which the driver balances the marine vessel when driving, the purpose being to move the thrust with respect to the marine vessel 10 and the longitudinal centre line. As can be seen, the first propulsion unit 32' indicated by dashed lines has been translatory displaced slightly towards port in order to increase the yaw leverage of the thrust the first outboard propulsion units 32 imparts with respect to the longitudinal centreline of the marine vessel 10. It has been found that this may be specifically useful when turning the marine vessel. It is thus very advantageous that at least one of the mounting portions, preferably all, may be translatory displaced when turning the marine vessel. This provides great trim capabilities to the marine vessel.

Hence in a general aspect, at least one of the mounting portions may be translatory displaced in order to increase the yaw leverage of the thrust, especially when turning the marine vessel. Likewise, and as can be gleaned from figure 6, at least one of the mounting portions may be translatory displaced in order to decrease the yaw leverage of the thrust. Each mounting portion disclosed herein may be provided with a vertical displacement mechanism and/or a tilt mechanism enabling the associated propulsion unit to be lifted out of the water and/or trimmed. The extension of the sliding rail 35 may vary, as disclosed above the extension of the sliding rail is horizontal, i.e. parallel with the still water line Sw. It should be noted however that the sliding rail may have different configurations. Figures 7a- 7d shows different embodiments of the sliding rail 35. For the sake of clarity, only half of the sliding rails 35 are shown and the associated propulsion unit is not shown. It should be noted that the sliding rails 35 are symmetrical in its form when comparing starboard and port side of the sliding rails 35. As can be seen, the sliding rail 35 may have different shapes. Figure 7a shows a sliding rail 35 having a slightly curved shape. Figure 7b shows the sliding rail 35 having a straight inclined shape, displacing the respective mounting portion upwards and towards the deck. It has been found that this may increase the leverage that the propulsion units impart to the marine vessel. Figure 7c has a first straight portion followed by an inclining straight directed portion. Figure 7d has a first straight portion and an inclined portion which substantially intersect each other at a gear station 36. The gear station 36 permits the selection of which sliding rail the propulsion unit should take. A driver, or the steering and thruster control module 26, or any other suitable ECU, may thus prompt the associated propulsion unit towards the desired position dependent on the situation and purpose of displacement.

According to an aspect, the disclosure also relates to a method for balancing the weight distribution of a marine vessel comprising at least a first and a second outboard propulsion unit. The marine vessel has a vertical axis, a transverse axis, and a

longitudinal axis. The method comprises the steps of displacing the first and the second outboard propulsion units with a translatory displacement in a direction along the transverse axis optionally as response to an input signal from an electronic control unit. Figure 8 shows a schematic block diagram for the purpose of illustrating an embodiment of the present invention.

With reference to figure 8; at step 100 a selected parameter is determined, such as the inclination, i.e. roll angle, turning angle and/or speed of the marine vessel using at least one sensor. Just as a matter of example, the heel of the marine vessel may be

continuously or intermittently measured via a gyro, or be measured upon a command via an input signal at a helm station. The sensor forwards the signal of the inclination to an ECU such as the steering and thruster control module. Just as a matter of example other sensors may be selected to gather data such as manual steering devices, automated steering device, a gyro, a throttle, an accelerometer, a speedometer, a fuel gauge, a water gauge, a GPS device, or combinations thereof.

At step 1 10 the ECU, in this case the steering and thruster control module, receives the sensor signal e.g. from a gyro. The received sensor signals are processed to determine if they should be followed by a consequence. The ECU may determine to act, or not to act. The ECU can optionally or additionally be prompted to act by a user, e.g. via the helm station of the marine vessel.

At step 120 an algorithm of the steering and thruster control module determines if the received signal is above or below a selected threshold value. The selected threshold value may be set by the driver, or it may be a pre-set value e.g. set as a roll stabilizing function. If the gyro signal is below the selected threshold value, no action is taken. If e.g. the selected parameter is velocity, and the sensor is a speedometer, it may be possible that a threshold value is set to prevent a too fast displacement of the propulsion units. At 130 the steering and thruster control module initiate a propulsion unit displacement 140 if the gyro signal is above a selected threshold value, or as optionally mentioned if the velocity of the marine vessel is below a selected threshold value.

It is to be understood that the present invention is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.