WO2005030575A1

WO2005030575A1 - Marine vessel vibration isolation mounts for an outboard drive structure

Info

Publication number: WO2005030575A1
Application number: PCT/NZ2004/000240
Authority: WO
Inventors: Aron Robert Henley
Original assignee: Henley Marine And Electrical Limited
Priority date: 2003-10-02
Filing date: 2004-10-04
Publication date: 2005-04-07

Abstract

A vibration isolation mounting (1) for location between a mounting of an outboard drive and a mounting structure (4) of a marine vessel, the mounting structure having a wall portion (4) comprising at least one vibration damping pad (6), located between the drive and the outboard side of the wall (4), at least one vibration damping bush (2) located in the mounting structure aperture and a fastener (15), the fastener (15) passing through and resiliently retaining the vibration damping pad (6), the vibration damping bush (2) and the outboard drive to the wall (4), allowing reduction in vibration and noise transmission of the outboard drive to the wall (4).

Description

MARINE VESSEL VIBRATION ISOLATION MOUNTS FOR AN OUTBOARD DRIVE STRUCTURE

FIELD OF THE INVENTION The present invention relates to vibration isolation mountings and in particular though not solely to vibration isolation units for mounting on a marine vessel between the hull and the outboard drive structure.

BACKGROUND OF THE INVENTION This invention also relates to the Marine Industry and is used on outboard- powered aluminium boats. The outboard drive structure of a marine vessel such as for example an outboard motor or stern drive, is subjected to a number of high and low frequency stresses and that may also be transmitted, via the connection to the boat hull. In particular with outboard drive units there are three main components that directly attribute to increased noise levels; the first is the power-head or engine of the drive unit; the second is the gearbox; and the third is the propeller. Any one of these three can make the difference between a smooth and quiet drive unit and a harsh unit. By insulating the outboard drive unit from the boat, it is possible to eliminate a large percentage of the induced resonance and vibration running through the hull and cabin and instruments. The vibration effect is exacerbated when the outboard mounting or hull material is stiff, such as aluminium, steel or, wood, or composite (e.g. glass fibre). When vibration is induced into aluminium, the inherently stiff material transmits the vibration and this is also heard as noise. Vibration is also hard on alloy boats and particularly on-board electronics and fittings, often causing fittings to shake loose or malfunction. It is therefore an object of the present invention to at least go some way to reducing the resonance and/or noise and/or vibration in outboard unit driven boats, or at least to provide the public with a useful choice. BRIEF DESCRIPTION OF THE INVENTION In first aspect the present invention may be said to consist in a vibration isolation mounting for location between a mounting of an outboard drive and a mounting structure of a marine vessel, the mounting structure having a wall portion, comprising or including: a. two vibration damping pads, located either side of the opening of a mounting structure aperture through said wall portion; b. one vibration damping bush located in said mounting structure aperture; and c. one fastener, said fastener passing through said first of said vibration damping pads, said vibration damping bush and the second of said vibration damping pads and said mounting, to provide a structure when said fastener is tightened to alleviate vibration transmission oF said outboard drive to said marine vessel. In a second aspect the present invention consists in a vibration isolation mounting for location between a mounting for an outboard drive and a hull form, comprising or including, a. at least one vibration damping pad to lie between said drive and the outboard side of said hull form, b. at least one vibration damping bush at least in part penetrating a mounting aperture of said hull form from the inboard side of said hull form, and c. a fastener, said fastener passing through and resiliently retaining, said at least one vibration damping pad, said at least one vibration damping bush, and said I t outboard drive, to said hull form, the resulting structure or assembly allowing reduction in vibration and noise transmission of said outboard drive to said hull form. Preferably said damping bush penetrates said mounting aperture of said hull form through to said vibration damping pad. Preferably said damping bush is of a top hat form when viewed in cross-section, with provision for a fastener to pass therethrough, the wider part of said damping bush locating on the inboard side of said hull form. Preferably said hull form aperture is provided by a mounted bush through said hull form. Preferably said mounted bush is reinforced in said hull form by welding and is flush mounted to said hull form on both sides. Preferably a cup form washer sits over said damping bush on said inboard side. Preferably said backing pad has a fastening member aperture to allow for adjustable mounting of said outboard drive. Preferably said outboard drive is an outboard motor. Alternatively said outboard drive is a stern drive or stern leg and is powered internally of said hull form. Preferably there are four vibration isolation mountings, one each for the mounting points of said outboard drive. Preferably said backing pad and damping bush are manufactured from a vibration absorbing material. Preferably said vibration absorbing material is urethane. Preferably a bond wire is located between said outboard drive structure and said hull form to form a connected electric structure for the purposes of alleviating galvanic corrosion. Preferably at least one of the mounting apertures of said outboard drive structure is in the form of a slot, and there are provided keys to sit at least in part in said slot to provide a single aperture for said fastener to pass through, and thus spread the load of said outboard drive structure more evenly. In another aspect the present invention consists in a method of vibrationally isolating an outboard drive structure of a marine vessel comprising the steps of: providing at least one mounting aperture through the hull form of said vessel, locating at least in part therein a damping bush, locating at least one backing pad between said hull and said outboard drive structure, and passing a fastener through said at least one damping bush, backing pad and outboard drive structure to locate said outboard drive structure to said hull form. In a further aspect the present invention consists in an outboard motor vibration isolation mounting to be interposed between a mounting zone of a hull of a marine vessel and a mounting structure of said outboard motor, said vibration isolation mounting comprising: a vibration absorbing material mounting pad disposed to the outboard side of the mounting zone of said hull and be interposed between said mounting structure of said outboard motor and said hull, a fastening means passing from the inboard side of said hull though a hull aperture and presented outboard of said hull to capture said outboard motor and said mounting pad to said hull, said fastening means isolated from the inboard side of said hull by a vibration isolating material washer. Preferably said fastening means is isolated from said hull by a vibration isolating material bush extending at least in part into said hull aperture. In a further aspect the present invention consists in a vibrational isolation mounting in or for a marine vessel hull comprising or including: capturing a vibrational insulating block either side of a mounting wall of said marine vessel hull, and an outboard drive structure mounting bracket, by passing a fastener from and through one side of said mounting wall to the other to retain said vibrational insulating blocks and said mounting bracket to said mounting wall to provide reduced transmission of vibration to said marine vessel hull. Preferably there is a vibration damping bush mounted intermediate of said vibrational insulating blocks, at least in part penetrating an aperture in said mounting wall, which said fastener passes through. In a further aspect the present invention consists in a backing pad for location between an outboard drive structure and a hull form as herein described with reference to any one or more of the accompanying drawings. In yet another aspect the present invention'consists in a mounting structure as herein described when fitted with a vibration isolation unit as herein described with reference to any one or more of the accompanying drawings. In yet another aspect the present invention consists in a kit of parts for fitting or retrofitting to a mounting structure with reference to any one or more of the accompanying drawings. In yet another aspect the present invention consists in a method of vibrationally isolating a drive structure as herein described with to any one or more of the accompanying drawings. In yet another aspect the present invention consists in a mounting key for use in a vibration isolation mounting as claimed herein and as herein described with reference to any one or more of the accompanying drawings. In yet a further aspect the present invention consists in a mounting jig for use in a vibration isolation mounting as claimed herein and as herein described with reference to any one or more of the accompanying drawings. In yet a further aspect the present invention consists in a backing pad for use in a vibration isolation mounting as claimed herein and as herein described with reference to any one or more of the accompanying drawings. In yet a further aspect the present invention consists in a backing pad as herein described when mounted between an outboard drive structure and a hull form, with reference to any one or more of the accompanying drawings. In yet a further aspect the present invention consists in a backing pad as herein described when mounted between an outboard drive structure and a hull form, with reference to any one or more of the accompanying drawings. In yet a further aspect still the present invention consists in a marine vessel which includes an outboard motor which has been mounted to the hull of said vessel using the mounting structure as herein described. The resonance and vibration that runs through the boat directly attributes to increased noise levels inside the boat and this invention reduces these noise levels. This invention involves fitting a urethane bush kit into the transom of the boat. The bush kit is made up of for example: 1) 4 x aluminium bushes that must be welded into the transom of the boat 2) 4 x moulded urethane stepped bushes that press inside the aluminium bushes that are welded into the transom of the boat 3) 4 x stainless steel cup washers that fit onto the front of the moulded urethane stepped bushes to retain the moulded urethane stepped bushes from moving. 4) 2 x universal moulded urethane backing pads that fit between the transom of the aluminium boat and the outboard motor. The outboard motor is bolted to the transom of the outboard-powered aluminium boat through the bush kit to insulate any resonance or vibration being transmitted into the aluminium boat. The outboard motor must also be connected back to the aluminium boat through a bonding wire to eliminate any electrolysis. To those skilled in the art to which the invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the scope of the invention as defined in the appended claims. The disclosures and the descriptions herein are purely illustrative and are not intended to be in any sense limiting.

BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the present invention will now be described with reference to the accompanying drawings where: Figure 1A shows in perspective view a mount bushing, Figure IB shows in perspective view a damping bush to sit partially inside the mount bushing, Figure 1C shows in perspective view a cup washer to sit over the top hat section of the damping bush, Figure ID shows in perspective view a damping pad for mounting between an outboard drive structure and the hull mounting point of the structure e.g. the transom, Figure IE shows a further series of views detailing the damping pad, Figure 2 shows in isometric the structure of the keys used for load transfer in the drive structure mounting plate, the 3 keys covering 5 different mount heights, Figure 3 shows an earthing strap using to run between the outboard drive structure and the a galvanic connection on the boat hull, Figure 4 shows an exploded view (not to scale) from the outboard perspective of the assembly of the cup washer, damping bush, mount bushing and damping pad, Figure 5 shows a section view along a fore aft line of the outboard drive structure transom mounting, Figure 5A) being where the mounting bush is the full thickness of the transom, and Figure 5B) where the mounting bush is welded to a transom section thinner than itself, both showing at least flush mounting on the outboard side, the inboard side being flush mounted when the transom and mount bush are the same thickness, Figure 6 shows a similar sectional view to that of Figure 5, where a jig is used to locate the mount bushes in the boat hull, prior to tack welding, removal of the jig, then full welding and flush mounting, e.g. by grinding, Figure 7 illustrates the preparation of the mounting point on the marine vessel, in this case the transom of a aluminium boat prior to installation or assembly of the current invention from Figure 7A) the outboard perspective and Figure 7B) the inboard perspective, Figure 8 shows the invention as laid out in a kit form prior to assembly, as might be sold, Figure 9 shows the change in vibration and noise measured before and after the fitting of the present invention to a typical boat, Figure 10 shows an exploded view of the assembly of the current invention, including the parts and also the transom of a vessel and the mounting plate of the outboard drive unit, illustrating the use of the key for slotting into the desired engine mount location, to locate the outboard drive structure more resiliently to the vibration isolation system, where Figure 10 A) shows the upper most mount position (position

1) is required using the first key, Figure 10B) shows a subsequent lower mount position (position 2) is required using the second key, Figure 10C) shows a central mount position (position 3) is required using the third key, Figure 10D) shows a subsequent lower mount position (position 4) is required using the reversed second key, Figure 10E) shows a lower most mount position (position 5) is required using the reversed first key, Figure 11 shows a close up of an outboard drive unit mounted via the present invention the transom of a boat, and *' ' Figure 12 shows a boat with an outboard motor mounted off the transom.

DETAILED DESCRIPTION OF THE INVENTION With references to Figures 1 through 12 there are shown a vibrational isolation and damping mounting (1). In the preferred embodiment the mounting consists of at least a damping bush (2), a mounted bush (3), washer member (5) and backing pad (6). The mounted bush 3 is of hollow internal construction with an internal diameter substantially the same as that of the external diameter of the top portion (2a) of the damping bush (2). The mounted bush (3) is of a material that can be welded or otherwise affixed and held in location to within or on the material comprising a mounting surface of a hull form. The dimensions of the mounted bush (3) are such that it can be flush-mounted through the thickness of the mounting surface of the marine vessel hull wall or may sit proud on the inboard side. The damping bush (2) in a preferred embodiment is made from an energy- absorbing material to damp out vibrations that may be imparted to it. For example, a urethane product which is largely resilient yet deformable under high energy loadings can be used. A urethane manufactured by Erapol™ under the name E83A is one example. The vibration isolation mounting uses urethane to insulate the motor from the aluminium boat as urethane has excellent noise and energy absorbing and damping properties. The damping bush (2) has a fastening aperture (2c) running therethrough which a fastener (15) can be passed through. The lower portion (2b) of the damping bush is of greater diameter than the upper portion (2a). The lower portion (2b) of the damping bush (2) sits proud of the mounted bush (3) on the inboard (10) side of a hull wall (4). A washer member (5), preferably in the form of a cup washer (however other forms of washer will suffice), with an internal diameter to match the external diameter of the lower portion (2b) of the damping bush (2) has a matching aperture therethrough to be axially in line with the fastener hole (2c) in the damping bush (2). The cup washer (5) is preferably made from a resilient material such as stainless steel or aluminium but other materials may be used where the loadings permit the use thereof. A backing pad (6) is shaped preferably complementary to the outboard drive structure mounting plate (18) to and against which it will be located. In the preferred embodiment there are two such backing pads (6) and their outer edges are contoured to match the plan profile of the mounting plate (18). The backing pads (6) have a number of apertures (6a) in one location and a second set of apertures (6b) in a second location. These are located so as to line up with the corresponding mounting apertures in the mounting plate of the outboard drive structure. The series of holes allow the drive structure to be mounted at varying heights whilst allowing the backing pad to move with the backing plate to these varying heights. In some instances, there are four holes such as shown in Figure Id, in other instances there are five holes (as shown in Figure le or Figure 10), or there are the number of holes that would be required to match the number of mounting options available on the outboard drive structure mounting plate (18). The backing pad (6) is preferably made of the same material as that of the mounting bush (2), i.e. some form of energy-absorbing material, in the preferred embodiment this material is a urethane, as above described. The mounting apertures (6a) and (6b) of the backing pad and the mounting plate apertures (20) allow, as stated, for a number of varying height mounting options. In some outboard drive structures manufactured, one or more of the locations for mounting, instead of having a series of apertures has actually a mounting plate slot (17) therethrough covering the distance the apertures otherwise would. This allows, for example, easier mounting of the outboard drive structure to the hull form. This occurs in situations where, for example, on the upper portion of the mounting plate there is a series of apertures (20) for a fastener (15) to allow the height to be varied and on the lower set, instead of the set of apertures, there is merely a mounting plate slot 17 which the fastener (15) passes through. Such an arrangement is undesirable from the prospect of securely locating the outboard drive structure to the hull form via the vibrational isolation mount of the present invention. Therefore, keys (8) are available which can be inserted into the mounting plate slot of the mounting plate (18). Where, for example, there are normally five mounting plate apertures (17) and a corresponding mounting plate slot (20) covering the distance of those five apertures then three keys can alternatively be used in the slot to match the varying heights of the five apertures. *^■' ' For example, a key (8a) with a semi-circular cut out at one end will cover height variations positions one and five corresponding to mounting plate apertures one and five as shown in Figure 10a and e. An offset hole through the middle of key (8b) can cover aperture mounting positions two and four, as shown in Figures 10b and d. The central position three, can be accommodated by a key (8c) with an aperture centrally therethrough, as shown in Figure lOc. The differing heights one and five, and two and four being achieved by flipping the key around as shown in Figure 10, namely, key (8a) cover mounting locations one and five, whereas key (8b) covers the second and fourth mounting location and (8c) covers the central or third mounting location. A bonding wire (9) connects a metallic or conductive element of the outboard drive structure to a corresponding metallic or conductive element in the hull form for the purposes of creating a single galvanic corrosion circuit as opposed to creating a separate galvanic cell on the outboard drive structure and that of the hull form. Alternative forms of the damping bush (2) present themselves where the upper section (2a) is separate from the lower section (2b). A smaller backing pad may be of a similar separate form to that of (2b) also, i.e. a smaller size similar to a thick urethane washer. In this situation, the order of assembly is not crucial in that the washer member (5) may be inboard (10) as earlier described or outboard (11). The resulting assembly having a damping washer (similar to lower section (2b)) either side of the mounting bush (3), within which is located a smaller damping bush effectively the same shape as (2a) only. The fastener is then passed through and the mounting plate (18) can them be mounted to the hull wall (4). Other embodiments of the components of the present invention are to be envisaged by a person skilled in the art and these are within the scope of the present invention. The installation of the vibrational isolation mounting and its components to a marine vessel (e.g. a boat 19) as previously described will now be outlined. In one example the vibrational isolation mounting may be applied to the transom (14) at the rear of a hull form. The process involves the creation of holes of sufficient diameter to locate the mounting bush (3) therein. The mounting procedure will be discussed in relation to the mounting' of an outboard motor which has four mount points thereon. The procedure, however, may be equally adapted to one or more vibrational isolation points and may be for other outboard drive structures such as a stern leg which has inboard powering and/or bow thrusters or similar hull mounting where a drive unit structure is to be located. The mounting bushes (3) can be located on a jig (16) which matches the (4) bolt mounting pattern on the mounting plate (18). The jig then holds the mounted bushes (3) rigidly in relation to the transom (14) and thereafter light tack welds (13) are utilised to hold the mounted bushes 3 in place in relation to the transom (14). The jig 16 is then removed and the mounted bushes (3) are fully welded (13) around their circumference on both the inboard side (10) and outboard side (11). The welded area of the mounted bush (3) and the transom (14) is then ground or machined to be substantially flat. Chamfers (3 a) at either end of the mounted bush (3) allow for the welding material to penetrate, at least in part, to the aperture in the transom (14) to more securely engage and retain the mounted bush (3). Once the four mounted bushes (3) are located correctly in place and welded and finished in the transom (14) the damping bushes in the form of urethane bushes (2) are pushed from the inboard side (10) into the apertures created by the mounted bushes. Thereafter the washer member (5) in the form of a cup washer is located over the damping bush part (2b) which rests on the inboard side (10) of the transom (14) and a fastener 15 is passed therethrough. The backing pad is then passed over the fastener through one of the apertures to match the mounting plate (18) from the outboard side (11). The outboard motor is then located and the fasteners (15) are passed through matching apertures in the outboard motor mounting plate (18) and the corresponding part of the fastener (e.g. a nut and washer) is passed there over to at least partially mount the outboard motor to the mounting. The invention may be sold as a kit comprising for example (for a 4 bolt mounting of an outboard drive structure): • 4x stainless-steel cup washers 5 • 4x urethane mount bushes • 4x aluminium tubes I • 2x urethane backing pads *" ' • lx earth lead 9 and stud • 2 set of anodised aluminium keys 8 (depending on outboard engine configuration) The backing pads 6 may also be individually sold as pairs for installation between a mounting plate 18 and hull wall via the normal installation method. The keys 8 may also be sold as a separate kit to more rigidly mount an outboard drive structure if so desired. Noise levels are measured in decibels. For example, we talk at about 70 decibels. Decibels are measured on an exponential scale. When the decibels go up a little, the noise actually goes up a lot. Provided below are some typical sounds and their dBA levels.

In order to prove the inventions ability to reduce noise levels and vibration, resulting in a more comfortable boating experience, the invention was fitted to 7.2m alloy boat. The boat runs a late model Mercury™ 200HP Optimax™ two-stroke engine. _^ X ' The first step was to record decibel levels and vibration readings from the boat before fitting the kit. These tests were carried out using a decibel meter measuring in dBA, and an accelerometer measuring vibration in metres per second. A point to note is that in hard-top aluminium boats, vibration and noise can be particularly intrusive due to the enclosed nature of the cabin and the fact there is no wind or air to disperse noise. The following results were recorded on a slight day on Auckland's Hauraki Gulf:

Installation involved removing the existing engine from the boat and drilling out the existing mount holes to 51mm in preparation for mounted bushes (3) to be welded into the boat transom (14). The mounted bushes 3 are retained on a jig plate (16) to align the mounted bushes (3) to the right hole centres for the outboard engine and the jig plate (16) is then clamped to the transom (14) ready for welding. The mounted bushes (3) are then tack-welded in place and the jig plate (16) is removed. The mounted bushes (3) are fully welded into the back of the transom (14) and cleaned up with a die grinder and disc sander so the weld (13) is flush on both sides of * ^■ X the transom (14) and the holes in the mounted bushes (3) are cleaned up. The damping bushes (2) are inserted into the mounted bushes (3) from inboard (11) of the transom (14) and the engine- mounting fasteners (15) push through the stainless- steel cup washers (5) through the front of the mounted bushes (3), leaving the fasteners (15) protruding on the outboard (11) side of the transom (14). The backing pads (6) are hung onto the fasteners (15) and the engine is swung back into place and bolted on. An earth strap (9) must be fitted between the outboard motor anode and the boat to protect against electrolysis. These results indicate a significant reduction in noise and vibration running through-out the boat. This installation also had a notable effect on the feel of the boat, reducing gear-change clunk, eliminating bow-rail vibration and under-foot resonance, while taming mid-range "growl" from the Mercury 200hp Optimax outboard.

Claims

CLAIMS:

1. A vibration isolation mounting for location between a mounting of an outboard drive and a mounting structure of a marine vessel, the mounting structure having a wall portion, comprising or including: a. two vibration damping pads, located either side of the opening of a mounting structure aperture through said wall portion; b. one vibration damping bush located in said mounting structure aperture; and c. one fastener said fastener passing through said first of said vibration damping pads, said vibration damping bush and the second of said vibration damping pads and said mounting, to provide a structure when said fastener is tightened to alleviate vibration transmission of said outboard drive to said marine vessel.

2. A vibration isolation mounting for location between a mounting for an outboard drive and a hull form, comprising or including, a. at least one vibration damping pad to lie between said drive and the outboard side of said hull form, b. at least one vibration damping bush at least in part penetrating a mounting aperture of said hull form from the inboard side of said hull form, and c. a fastener said fastener passing through and resiliently retaining, said at least one vibration damping pad, said at least one vibration damping bush, and said outboard drive, to said hull form, the resulting structure or assembly allowing reduction in vibration and noise transmission of said outboard drive to said hull form.

3. A vibration isolation mounting as claime'd in claim 2 wherein said damping bush penetrates said mounting aperture of said hull form through to said vibration damping pad.

4. A vibration isolation mounting as claimed in either claim 2 or claim 3 wherein said damping bush is of a top hat form when viewed in cross-section, with provision for a fastener to pass therethrough, the wider part of said damping bush locating on the inboard side of said hull form.

5. A vibration isolation mounting as claimed in any one of claims 2 to 4 wherein said hull form aperture is provided by a mounted bush through said hull form.

6. A vibration isolation mounting as claimed in any one of claims 2 to 5 wherein said mounted bush is reinforced in said hull form by welding and is flush mounted to said hull form on both sides.

7. A vibration isolation mounting as claimed in any one of claims 2 to 6 wherein a cup form washer sits over said damping bush on said inboard side.

8. A vibration isolation mounting as claimed in any one of claims 2 to 7 wherein said backing pad has a fastening member aperture to allow for adjustable mounting of said outboard drive.

9. A vibration isolation mounting as claimed in any one of claims 2 to 8 wherein said outboard drive is an outboard motor.

10. A vibration isolation mounting as claimed in any one of claims 2 to 8 wherein said outboard drive is a stern cirive or stern leg and is powered internally of said hull form.

11. A vibration isolation mounting as claimed in any one of claims 2 to 10 wherein there are four vibration isolation mountings, one each for the mounting points of said outboard drive.

12. A vibration isolation mounting as claimed in any one of claims 2 to 11 wherein said backing pad and damping bush are manufactured from a vibration absorbing material.

13. A vibration isolation mounting as claimed in claim 12 wherein said vibration absorbing material is urethane.

14. A vibration isolation mounting as claimed in any one of claims 2 to 13 wherein a bond wire is located between said outboard drive structure and said hull form to form a connected electric structure for the purposes of alleviating galvanic corrosion.

15. A vibration isolation mounting as claimed in any one of claims 2 to 14 wherein at least one of the mounting apertures of said outboard drive structure is in the form of a slot, and there are provided keys to sit at least in part in said slot to provide a single aperture for said fastener to pass through, and thus spread the load of said outboard drive structure more evenly.

16. A method of vibrationally isolating an outboard drive structure of a marine vessel comprising the steps of: providing at least one mounting aperture through the hull form of said vessel, locating at least in part therein a damping bush, locating at least one backing pad between said hull and said outboard drive structure, and passing a fastener through said at least one damping bush, backing pad and outboard drive structure to locate said outboard drive structure to said hull form.

17. An outboard motor vibration isolation mounting to be interposed between a mounting zone of a hull of a marine vessel and a mounting structure of said outboard motor, said vibration isolation mounting comprising: a vibration absorbing material mounting pad disposed to the outboard side of the mounting zone of said hull and be interposed between said mounting structure of said outboard motor and said hull, a fastening means passing from the inboard side of said hull though a hull aperture and presented outboard of said hull to capture said outboard motor and said mounting pad to said hull, said fastening means isolated from the inboard side of said hull by a vibration isolating material washer.

18. An isolation mounting as claimed in claim 17 wherein said fastening means is isolated from said hull by a vibration isolating material bush extending at least in part into said hull aperture.

19. A vibrational isolation mounting in or for a marine vessel hull comprising or including: capturing a vibrational insulating block either side of a mounting wall of said marine vessel hull, and an outboard drive structure mounting bracket, by passing a fastener from and through one side of said mounting wall to the other to retain said vibrational insulating blocks and said mounting bracket to said mounting wall to provide reduced transmission of vibration to said marine vessel hull.

20. A vibrational isolation mounting as claimed in claim 19 wherein there is a vibration damping bush mounted intermediate of said vibrational insulating blocks, at least in part penetrating an aperture in said mounting wall, which said fastener passes through.

21. A backing pad for location between an outboard drive structure and a hull form as herein described with reference to any one or more of the accompanying drawings.

22. A mounting structure as herein described when fitted with a vibration isolation unit as herein described with reference to any one or more of the accompanying drawings.

23. A kit of parts as claimed in any one or more of claims 1 to 15 for fitting or retrofitting to a mounting structure with reference to any one or more of the accompanying drawings.

24. A method of vibrationally isolating a drive structure as herein described with to any one or more of the accompanying drawings.

25. A mounting key for use in a vibration isolation mounting as claimed herein and as herein described with reference to any one or more of the accompanying drawings.

26. A mounting jig for use in a vibration isolation mounting as claimed herein and as herein described with reference to any one or more of the accompanying drawings.

27. A backing pad for use in a vibration isolation mounting as claimed herein and as herein described with reference to any one or more of the accompanying drawings.

28. A backing pad as herein described when mounted between an outboard drive structure and a hull form, with reference to any one or more of the accompanying drawings.

29. A backing pad as herein described when mounted between an outboard drive structure and a hull form, with reference to any one or more of the accompanying drawings. -"^" '

30. A marine vessel which includes an outboard motor which has been mounted to the hull of said vessel using the mounting structure as claimed in any one of claims 1 to 16.