EP4035988A1

EP4035988A1 - Drive arrangement for a marine vessel

Info

Publication number: EP4035988A1
Application number: EP21153772.5A
Authority: EP
Inventors: Lennart Arvidsson; Annika Lindqvist
Original assignee: Volvo Penta AB
Current assignee: Volvo Penta AB
Priority date: 2021-01-27
Filing date: 2021-01-27
Publication date: 2022-08-03
Also published as: US20220234707A1

Abstract

The invention relates to a drive arrangement (1, 2) for a marine vessel (10), the drive arrangement (1, 2) comprising: an upper drive part (4) configured to be mounted onto an outside of a transom (3) of the marine vessel (10); a lower drive part (5) connected to the upper drive part (4) so as to be fixed in a vertical direction in relation to the upper drive part (4), wherein the lower drive part (5) has a hydrodynamic configuration and is provided with at least one propeller (6); and a transmission system (7, 8, 9) arranged to transfer a drive torque to the propeller (6) from a drive source system (20, 21, 22, 23) connected to the transmission system, wherein an outer surface of the upper drive part (4) substantially is made up of a plurality of surface sections (41-51) connected by one or more edges (60), wherein each of said surface sections (41-51) has a shape corresponding to a so-called ruled surface that can be generated by the motion of a straight line, such as a planar surface or a lateral surface of a cylinder or cone.

Description

TECHNICAL FIELD

The invention relates to a drive arrangement for a marine vessel. The invention also relates to a marine vessel provided with such a drive arrangement.
The invention may typically be applied to marine vessels such as a powerboat but may also be applied to other types of marine vessels.

BACKGROUND

Marine vessels, such as powerboats, may be equipped with a propulsion system in the form of an inboard/outboard system including a stern drive assembly mounted onto a transom of the marine vessel and a drive source system, such as an internal combustion engine or an electric motor, arranged on-board the vessel inside of the transom. Such a vessel is steered by pivoting the drive assembly from side to side. US6468119B1 shows an example of an inboard/outboard system of the above type.
A well-known problem related to such systems is that the stern drive assembly, or at least the upper parts thereof, often becomes covered with marine organisms, such as barnacles, since the entire drive assembly typically is positioned below the waterline when the vessel or boat is moored. Although various anti-fouling methods are known there is often a need to manually and mechanically remove the barnacles etc. This can be rather tiring and also difficult as there are a lot of joints and small narrow spaces (bolt and nut pockets, hydraulic oil hoses, seals, ground wires, bellows, etc.) in a typical stern drive assembly where marine organisms are prone to grow.
There is thus a need for reducing problems related to growth of marine organisms onto drive arrangements mounted onto a transom of a marine vessel.

SUMMARY

The invention concerns a drive arrangement for a marine vessel, in particular a powerboat or similar. The drive arrangement comprises an upper drive part configured to be mounted onto an outside of a transom of the marine vessel; a lower drive part connected to the upper drive part so as to be fixed in a vertical direction in relation to the upper drive part, wherein the lower drive part has a hydrodynamic configuration and is provided with at least one propeller; and a transmission system arranged to transfer a drive torque to the propeller from a drive source system connected to the transmission system, wherein the transmission system is arranged to be connected to a drive source system located at least partly on-board the marine vessel inside of the transom, wherein the transmission system comprises a first drive shaft member extending vertically between the upper and lower drive parts and a second drive shaft member extending substantially horizontally in the lower drive part, and wherein the second drive shaft member is connected to the first drive shaft member and to the at least one propeller.
The upper drive part is intended to be located behind the transom and substantially above an imaginary extension of a hull bottom of the marine vessel when mounted onto the transom, and the lower drive part is intended to be located substantially below the imaginary extension of the hull bottom of the marine vessel, and/or substantially below the real hull bottom of the marine vessel, when the upper drive part of the drive arrangement is mounted onto the transom.
Further, an outer surface of the upper drive part substantially is made up of a plurality of surface sections connected by one or more edges, wherein each of said surface sections has a shape corresponding to a so-called ruled surface that can be generated by the motion of a straight line, such as a planar surface or a lateral surface of a cylinder or cone.
The features concerning lower drive part vertically fixed to upper drive part, hydrodynamic shape of lower drive part, drive source system located at least partly inside of the transom, drive shaft members, etc., have been included to define a drive arrangement suitable for powerboats and similar and to clearly distinguish from other types of drive arrangements that might be mounted to an outside of a transom of various marine vessels. When planing with a powerboat provided with a drive arrangement of the above type, the upper drive part will typically be located above the waterline. However, when the same powerboat is moored, both the upper and lower drive parts will typically be located below the waterline.
An upper drive part having an outer surface as defined above and being covered with barnacles or other marine organisms can relatively easily be cleaned using a scraper tool since a straight scraper blade can come in contact with substantially the entire outer surface (since a straight scraper can be moved along a ruled surface in a way similar to "the motion of the straight line" mentioned above). To simplify the cleaning work it is of course an advantage to reduce as much as possible the presence of bolt and nut pockets, hoses, wires etc., outside of the outer surface of the upper drive part and thus prevent such parts from coming in contact with sea water.
In a particularly advantageous embodiment, the upper drive part is fixed to the transom and, preferably, the lower drive part is rotatable in relation to the upper drive part for steering, i.e. the lower drive part is rotatable about a vertical axis whereas the upper drive part is fixed. By fixing the upper drive part to the transom, which is in contrast to conventional stern drives where the entire drive arrangement is pivotable/swingable for steering, no pivot components are required between the drive arrangement and the transom, and the other components normally required, such as hydraulic oil hoses, ground wires etc., can all be arranged inside e.g. an openable hood or similar of the upper drive part where the hood has an outer surface as specified above. Further, it is not necessary to use bellows or similar to try to seal e.g. any pivot connection between the upper drive part and the transom. Instead the upper drive part and the hood can be connected directly to the transom. This particularly advantageous embodiment is further described below.
It should be noted that terms like upper, lower, vertical and horizontal refer to the general relative position or general direction when the drive arrangement is mounted onto a marine vessel. As to vertical and horizontal, these terms only mean that a certain direction is roughly vertical or horizontal. For instance, the hull bottom of the marine vessel may very well be V-shaped which typically would mean that the drive arrangement will be mounted to the transom in a non-centred position and at some angle, for instance 10-20°, in relation to the true vertical direction (see figure 1). Also in such situations it is considered in this disclosure that something that extends along the drive arrangement extends vertically, as an example it is still considered that the first drive shaft extends vertically between the upper and lower drive parts.
As indicated above, each of the surface sections of the outer surface may be planar/flat or have the shape resembling e.g. a portion of the lateral surface of a cylinder or cone. The outer surface may thus have or include a faceted shape comprising two or more flat surface sections connected by one or more straight edges. Such a faceted shape may be complemented with surface sections having the shape of e.g. a (part of) cylinder or a (part of) cone.
In one example the outer surface can have the general shape of a rectangular parallelepiped, i.e. a regular box, including at least four planar surface sections, left (port side) and right (starboard side) parallel surface sections, an upper surface section and a rear (astern) surface section. A planar lower surface section may fully or partly surround the lower drive part depending on the particular structure of the drive arrangement as a whole. When the upper drive part is to be fixed directly to the transom there might be no outer surface on the forward side of the upper drive part since this side will be in contact with the transom when mounted to the vessel. The outer surface may include a smaller parallelepiped or a cylinder located on top of the parallelepiped mentioned above, for instance for the purpose of creating room for a particular component inside.
In another example the outer surface can have the general shape of a tetrahedron, i.e. a triangular pyramid, with two sides connected along a common edge and one side intended to be connected to the transom with the common edge extending rearwards (aftwards) and downwards.
The outer surface of the upper drive part may of course include a higher number of surface sections and be more complex than exemplified above. For instance, the outer surface may include a faceted shape comprising e.g. 6-10 flat surface sections arranged side by side and on top of each other and connect the surface sections by several straight edges. Also such a more complex structure may be complemented with surface sections having the shape of e.g. a part of a cylinder, for instance by arranging flat surface sections side by side in a lower zone of the upper drive part, arranging a flat horizontal surface section as a lid onto the surface sections in the lower zone, arranging an open circular cylinder onto the flat horizontal surface section, and arranging a circular disc lid at the top of the cylinder (and providing the horizontal surface section with an opening inside the cylinder so as to allow for a component inside the upper drive part, such as an electric motor configured to provide a drive torque to the propeller, to project upwards and be enclosed by the outer surface even if it projects beyond the flat horizontal surface section).
The surface sections should not be too small since a lot of surface sections would be required and the cleaning work would not be significantly simplified. Although a few small surface sections may be acceptable, most surface sections should have a surface area of at least around 25 cm³.
A more complex design of the surface sections may also be used to give the outer surface a more hydrodynamic (and appealing) design than, for instance, a rectangular parallelepiped. However, the hydrodynamic properties of the upper drive part are not critical and need not be optimized since the upper drive part does not impact hydrodynamic drag significantly as this this part is located above the waterline when the marine vessel is planing and drag resistance is important.
That the lower drive part has a hydrodynamic configuration means that it is shaped to generate a low drag resistance. The lower drive part thus has at least partly a wing-like shape with a width that varies along a forward-aftward direction of the lower drive part.
In an embodiment, the outer surface of the upper drive part comprises at least two flat surface sections connected by a straight edge. In a further embodiment the outer surface of the upper drive part comprises at least three, preferably more, flat surface sections connected by straight edges. A plurality of adjacent flat surface sections may be arranged in a faceted shape.
In an embodiment, the outer surface of the upper drive part comprises at least a part of a lateral side of a cylinder.
In an embodiment, the plurality of surface sections are arranged to generally be facing sideways, upwards and/or backwards in relation to the marine vessel when the upper drive part is mounted onto the transom. A forward side of the upper drive part may be in contact with the transom. In case the drive arrangement is of the conventional swingable stern drive type, the forward side of the upper drive part might be equipped with hinge members, hoses, etc., but parts of that side might still be provided with one or more surface sections of the above type.
In an embodiment, the plurality of surface sections covers at least 70%, preferably at least 80%, more preferably at least 90%, of the total outer surface of the upper drive part facing generally sideways, upwards and/or backwards in relation to the marine vessel when the upper drive part is mounted onto the transom. The more, the better, for cleaning purposes.
In an embodiment, the upper drive part is arranged to be mounted to the transom via a hinge element so as to allow the upper and lower drive parts to pivot from side to side. This includes e.g. a conventional stern drive assembly.
In an embodiment, the upper drive part is arranged to be fixedly mounted onto the transom. This means that the upper drive is not allowed nor intended to pivot from side to side, which further means that no particular measures need to be taken for allowing pivoting, i.e. hinge members, extended hoses, or bellows etc. are not required. Instead such components can be arranged inside the upper drive member that can be mounted with its forward (open) side in contact with the transom. All exposed sides of the upper drive unit facing sideways and upwards may then be provided with easily cleaned surface sections of the above mentioned type.
In an embodiment, the lower drive part is rotatable about a vertical axis in relation to the upper drive part. Although this is applicable also to a swingable drive arrangement, it is of particular advantage for the variant where the upper drive part is arranged to be fixedly mounted onto the transom as it allows the drive arrangement to be used for steering of the marine vessel. Whereas the upper drive part is fixed, the lower drive part is rotatable about a vertical axis so that the propeller can be directed in different directions. The lower drive part may thus be of a type often referred to as pod drives, which normally are mounted to the bottom hull of the boat.
In an embodiment, the drive source system forms part of the drive arrangement, and wherein the drive source system comprises i) an internal combustion engine intended to be located on board the marine vessel inside of the transom or ii) an electric motor and an electric energy storage unit for powering the electric motor, wherein at least the electric energy storage unit is intended to be located on board the marine vessel inside of the transom. The drive source system may include both an internal combustion engine and an electric driveline. The electric motor may be arranged inside the upper drive part, at least if it is a relatively small electric motor. Such a small electric motor preferably forms part of a drive source system comprising also an internal combustion engine, or a larger electric engine. A larger electric engine is preferably arranged on-board the vessel inside of the transom, or partly inside the upper drive unit and partly on-board the vessel if extending through an opening in the transom into the upper drive part. In any case, if the drive source system includes a large electric energy storage unit for powering of an electric motor, such a storage unit is preferably arranged on-board the vehicle as it is likely to be too large and heavy for being arranged in the upper drive part.
The invention also concerns a marine vessel provided with a drive arrangement comprising: an upper drive part mounted onto an outside of a transom of the marine vessel; a lower drive part connected to the upper drive part so as to be fixed in a vertical direction in relation to the upper drive part, wherein the lower drive part has a hydrodynamic configuration and is provided with at least one propeller; and a transmission system arranged to transfer a drive torque to the propeller from a drive source system connected to the transmission system, wherein the drive source system is located at least partly on-board the marine vessel inside of the transom, wherein the transmission system comprises a first drive shaft member extending vertically between the upper and lower drive parts and a second drive shaft member extending substantially horizontally in the lower drive part, and wherein the second drive shaft member is connected to the first drive shaft member and to the at least one propeller.
The upper drive part is located behind the transom and substantially above an imaginary extension of a hull bottom of the marine vessel, and the lower drive part is located substantially below the imaginary extension of the hull bottom of the marine vessel and/or substantially below the real hull bottom of the marine vessel.
Further, the outer surface of the upper drive part is substantially made up of a plurality of surface sections connected by one or more edges, wherein each of said surface sections has a shape corresponding to a so-called ruled surface that can be generated by the motion of a straight line, such as a planar surface or a lateral surface of a cylinder or cone.
In an embodiment of the marine vessel, the upper drive part is fixedly mounted onto the transom.
In an embodiment of the marine vessel, the lower drive part is rotatable in relation to the upper drive part.
In an embodiment of the marine vessel, the drive source system forms part of the marine vessel and the drive source system comprises an internal combustion engine or an electric motor located on board the marine vessel inside of the transom.
In an embodiment of the marine vessel, the drive source system forms part of the marine vessel and the drive source system comprises an electric motor at least partly arranged in the upper drive part.
In an embodiment of the marine vessel, the drive source system forms part of the marine vessel and comprises an electric motor and an electric energy storage unit, wherein the electric energy storage unit is located on board the marine vessel inside of the transom.

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:

Figure 1 shows a marine vessel provided with two drive arrangements according to this disclosure.
Figure 2 shows a partly sectional side view of a first embodiment of a drive arrangement according to this disclosure.
Figure 3 shows a partly sectional side view of a second embodiment of a drive arrangement according to this disclosure.
Figure 4 shows a perspective view of one of the drive arrangements according to figure 1.
Figure 5 shows an alternative exterior structure of an upper drive part of the drive arrangement.
Figure 6 shows a further alternative exterior structure of the upper drive part of the drive arrangement.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

Figure 1 shows a marine vessel 10 in the form of a powerboat having a transom 3 and a hull bottom 11. First and second drive arrangements 1, 2 are mounted side by side onto an outside of the transom 3. The two drive arrangements 1, 2 are in this case similar. For the different embodiments and variants of the drive arrangement shown in the following figures, only reference number 1 is used. The drive arrangements shown in figures 2-4 correspond to the drive arrangements 1, 2 shown in figure 1 as regards the outer parts and shape. Figures 2-3 show two alternative drive arrangements as regards the internal structure. Figures 5-6 show alternative exterior structures of an upper drive part of the drive arrangement. A marine vessel may be provided with one, two, three or more drive arrangements of the type described in this disclosure.
As shown in figures 2-3, the drive arrangement 1, 2 has an upper drive part 4 and a lower drive part 5. The upper drive part 4 is here fixedly connected to the transom 3, i.e. the upper drive part 4 is not intended to be movable in relation to the vessel 10. The lower drive part 5 is connected to, and fixed in a vertical direction in relation to, the upper drive part 4. The lower drive part 5 is provided with a propeller 6, in this example a forwardly directed double propeller, and the lower drive part 5 has a hydrodynamic configuration to reduce drag resistance. The lower drive part 5 is rotatable about a vertical axis in a pod drive manner in relation to the upper drive part 4 so that the propeller 6 can be directed in different directions for steering of the marine vessel 10.
A transmission system is arranged to transfer a drive torque to the propeller 6 from a drive source system connected to the transmission system. The drive source system is further described below. The transmission system comprises a first drive shaft member 8 that extends substantially vertically between the upper and lower drive parts 4, 5 and a second drive shaft member 9 extending substantially horizontally in the lower drive part 5. The second drive shaft member 9 is connected to the first drive shaft member 8 and to the at least one propeller 6. A further drive shaft member 7 is indicated in figure 2.
The transmission system may be arranged in different ways and only examples of general designs are shown in this disclosure. As an example, the first or second drive shaft members 8, 9 does not necessarily have be formed by one single drive shaft but may include several components.
As shown in figures 2-3, the upper drive part 4 is located behind the transom 3 and substantially above an imaginary extension of the hull bottom 11. In fact, an underside of the upper drive part 4 is aligned with the hull bottom 11 of the marine vessel 10. Consequently, the lower drive part 5 is located below the imaginary extension of the hull bottom 11 of the marine vessel 10. The lower drive part 5 is partly located also below the real hull bottom 11 of the marine vessel 10, in particular because the propeller 6 in this case is forward directed.
As shown in figures 1 and 4-6, and as indicated in figures 2-3, an outer surface of the upper drive part 4 is substantially, in this case fully, made up of a plurality of surface sections 41-51 connected by one or more edges 60. Each of these surface sections 41-51 has a shape corresponding to a so-called ruled surface that can be generated by the motion of a straight line, such as a planar surface or a lateral surface of a cylinder or cone.
The principal shape of the outer surface of the upper drive part 4 is not affected by the drive source system, although some adaptations to certain drive source systems is possible as further described below, but an explanation of the drive source system is useful for the understanding of what kind of drive arrangements and marine vessels this disclosure relates to.
Figure 2 shows a drive source system comprising an internal combustion engine (ICE) 20 and a (small) electric motor 21. The ICE 20 is arranged on-board the marine vessel 10 inside of the transom 3 and is connected to the propeller 6 via drive shaft members 7, 8 and 9. The electric motor 21 is arranged in the upper drive part 4 and is connected directly to the (vertical) first drive shaft member 8. The electric motor 21 is intended for low-speed operation of the marine vessel 10, whereas the ICE 20 forms the main drive source.
Figure 3 shows a drive source system comprising a (large) electric motor 22 arranged partly in the upper drive part 4 and partly on-board the marine vessel 10 inside of the transom 3; it thus extends through an opening in the transom 3. The drive source system further comprises an electric energy storage unit (not shown), i.e. a "battery", arranged on-board the marine vessel 10 inside of the transom 3. A cord 23 indicates an electric connection between the electric motor 22 and the electric energy storage unit. The electric motor 22 is connected to the first drive shaft 8 and forms in this case the main, and only, drive source for the propeller.
As shown in figures 1 and 4, the outer surface of the upper drive part 4 comprises all together ten flat surface sections 41, 42, 43, 44 connected by straight edges 60 and arranged to form a faceted shape. Six surface sections, three on each side, form a lower faceted shape, and four surface sections, two on each side, form an upper faceted shape in the form of a "roof" onto the lower faceted shape. As an alternative, the "roof" might be one large flat surface section placed onto the lower faceted shape. However, a raised "roof" as exemplified in figures 1 and 4 provides additional room inside the upper drive part 4 for housing e.g. the electric motor located above the first drive shaft member 8.
The upper drive part 4 is preferably provided with a detachable or foldable hood and, if so, the outer surface of the hood can be provided with the ruled surface sections.
Figure 5 shows an alternative embodiment of the outer surface of the upper drive part 4 where the outer surface comprises only two flat surface sections 45, 46 connected by one straight edge 60.
Figure 6 shows a further alternative embodiment of the outer surface of the upper drive part 4 where the lower part is a faceted shape similar to figures 1 and 4 but where a flat horizontal surface section 49 forms a main roof and where a cylinder with lateral side 47 and upper side 48 forms a projecting roof and provides additional space inside the upper drive part 4.
Various other possibilities exist for arranging the outer surface of the upper drive part 4.
As can be seen in figures 1 and 4-6, the plurality of surface sections are arranged to generally be facing sideways, upwards and/or backwards in relation to the marine vessel 10 when the upper drive part 4 is mounted onto the transom 3. Moreover, the plurality of surface sections covers in these examples 100% of the total outer surface of the upper drive part facing generally sideways, upwards and/or backwards in relation to the marine vessel 10 when the upper drive part 4 is mounted onto the transom 3. However, it is not necessary that the entire outer surface is covered with said surface sections.
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.

Claims

Drive arrangement (1, 2) for a marine vessel (10), the drive arrangement (1, 2) comprising:
- an upper drive part (4) configured to be mounted onto an outside of a transom (3) of the marine vessel (10);

- a lower drive part (5) connected to the upper drive part (4) so as to be fixed in a vertical direction in relation to the upper drive part (4), wherein the lower drive part (5) has a hydrodynamic configuration and is provided with at least one propeller (6); and

- a transmission system (7, 8, 9) arranged to transfer a drive torque to the propeller (6) from a drive source system (20, 21, 22, 23) connected to the transmission system, wherein the transmission system is arranged to be connected to a drive source system located at least partly on-board the marine vessel (10) inside of the transom (3), wherein the transmission system comprises a first drive shaft member (8) extending vertically between the upper and lower drive parts (4, 5) and a second drive shaft member (9) extending substantially horizontally in the lower drive part (5), and wherein the second drive shaft member (9) is connected to the first drive shaft member (8) and to the at least one propeller (6),
wherein the upper drive part (4) is intended to be located behind the transom (3) and substantially above an imaginary extension of a hull bottom (11) of the marine vessel (10) when mounted onto the transom (3),

wherein the lower drive part (5) is intended to be located substantially below the imaginary extension of the hull bottom (11) of the marine vessel (10), and/or substantially below the real hull bottom (11) of the marine vessel (10), when the upper drive part (4) of the drive arrangement (1, 2) is mounted onto the transom (3), and

wherein an outer surface of the upper drive part (4) substantially is made up of a plurality of surface sections (41-51) connected by one or more edges (60), wherein each of said surface sections (41-51) has a shape corresponding to a so-called ruled surface that can be generated by the motion of a straight line, such as a planar surface or a lateral surface of a cylinder or cone.
Drive arrangement according to claim 1, wherein the outer surface of the upper drive part comprises at least two flat surface sections connected by a straight edge.
Drive arrangement according to claim 1 or 2, wherein the outer surface of the upper drive part comprises at least three, preferably more, flat surface sections connected by straight edges.
Drive arrangement according to any of claims 1-3, wherein the outer surface of the upper drive part comprises at least a part of a lateral side of a cylinder.
Drive arrangement according to any of the above claims, wherein the plurality of surface sections are arranged to generally be facing sideways, upwards and/or backwards in relation to the marine vessel when the upper drive part is mounted onto the transom.
Drive arrangement according to any of the above claims, wherein the plurality of surface sections covers at least 70%, preferably at least 80%, more preferably at least 90%, of the total outer surface of the upper drive part facing generally sideways, upwards and/or backwards in relation to the marine vessel when the upper drive part is mounted onto the transom.
Drive arrangement according to any of the above claims, wherein the upper drive part is arranged to be mounted to the transom via a hinge element so as to allow the drive arrangement to pivot from side to side.
Drive arrangement according to any of claims 1-7, wherein the upper drive part is arranged to be fixedly mounted onto the transom.
Drive arrangement according to any of the above claims, wherein the lower drive part is rotatable about a vertical axis in relation to the upper drive part.
Drive arrangement according to any of the above claims, wherein the drive source system forms part of the drive arrangement, and wherein the drive source system comprises i) an internal combustion engine intended to be located on board the marine vessel inside of the transom or ii) an electric motor and an electric energy storage unit for powering the electric motor, wherein at least the electric energy storage unit is intended to be located on board the marine vessel inside of the transom.
Marine vessel (10), wherein the marine vessel (10) is provided with a drive arrangement (1, 2) comprising:
- an upper drive part (4) mounted onto an outside of a transom (3) of the marine vessel (10);

- a lower drive part (5) connected to the upper drive part (4) so as to be fixed in a vertical direction in relation to the upper drive part (4), wherein the lower drive part (5) has a hydrodynamic configuration and is provided with at least one propeller (6); and

- a transmission system (7, 8, 9) arranged to transfer a drive torque to the propeller (6) from a drive source system (20, 21, 22, 23) connected to the transmission system, wherein the drive source system is located at least partly on-board the marine vessel (10) inside of the transom (3), wherein the transmission system comprises a first drive shaft member (8) extending vertically between the upper and lower drive parts (4, 5) and a second drive shaft member (9) extending substantially horizontally in the lower drive part (5), and wherein the second drive shaft member (9) is connected to the first drive shaft member (8) and to the at least one propeller (6),
wherein the upper drive part (4) is located behind the transom (3) and substantially above an imaginary extension of a hull bottom (11) of the marine vessel (10),

wherein the lower drive part (5) is located substantially below the imaginary extension of the hull bottom (11) of the marine vessel (10) and/or substantially below the real hull bottom (11) of the marine vessel (10), and

wherein an outer surface of the upper drive part (4) substantially is made up of a plurality of surface sections (41-51) connected by one or more edges (60), wherein each of said surface sections (41-51) has a shape corresponding to a so-called ruled surface that can be generated by the motion of a straight line, such as a planar surface or a lateral surface of a cylinder or cone.
Marine vessel according to claim 11, wherein the upper drive part is fixedly mounted onto the transom.
Marine vessel according to claim 11 or 12, wherein the lower drive part is rotatable about a vertical axis in relation to the upper drive part.
Marine vessel according to any of claims 11-13, wherein the drive source system forms part of the marine vessel and wherein the drive source system comprises an internal combustion engine or an electric motor located on board the marine vessel inside of the transom.
Marine vessel according to any of claims 11-14, wherein the drive source system forms part of the marine vessel and wherein the drive source system comprises an electric motor at least partly arranged in the upper drive part.
Marine vessel according to any of claims 11-15, wherein the drive source system forms part of the marine vessel and comprises an electric motor and an electric energy storage unit, wherein the electric energy storage unit is located on board the marine vessel inside of the transom.