Patent Publication Number: US-2011073032-A1

Title: Underwater protective system to inhibit marine growth

Description:
BACKGROUND OF THE INVENTION 
     A. Field 
     This invention relates generally to marine equipment protective devices, and more particularly to a protective cover for propellers, transducers and other underwater components to protect against marine growth. 
     B. Description of Related Art 
     Underwater components, particularly propellers and connected propeller shafts, transducers and the like, are susceptible to the development of marine growth when submerged in sea water. Such growth can include barnacles, sea grass, slime, etc. (collectively referred to has “marine growth”). Marine growth that attaches to propellers remains attached even when the propeller turns to propel the boat at typical cruising speeds. Marine growth can significantly reduce the efficiency of the boat&#39;s propulsion system. Accordingly, countermeasures to ameliorate marine growth attaching to propellers have been proposed. 
     These countermeasures can take a variety of forms. One is to hire a diver to scrub and clean the propeller at regular intervals, or in advance of a voyage. Another is to apply an antifouling paint to the propeller. The art has further developed a variety of protective devices that are designed to cover or protect marine propulsion apparatus while in the water. Such protective devices are described in the patent literature, and include Sloan, U.S. Pat. No. 3,220,374; Pearce, U.S. Pat. No. 3,587,508; Crepeau, U.S. Pat. No. 6,916,217; Morton, U.S. Pat. No. 6,152,064; and Borrelli, U.S. Pat. No. 6,190,220. Other patents of interest include Ojeda, U.S. Pat. No. 5,273,399; Newman, U.S. Pat. No. 4,826,461; Doelcher, U.S. Pat. No. 5,527,193 and Lobrovich, U.S. Pat. No. 7,244,154. 
     The present protective system of this disclosure is considered an improvement over the devices shown in these patents in that it is particularly suitable for propellers, transducers and other underwater components that are submerged substantially below the waterline (e.g., as in most medium and larger sailboats and power boats due the installation of inboard diesel or gas engines) yet can be readily released by the user/boat owner from above the water before their trip, without requiring a diver to release the protective system. The solutions proposed for example by the Sloan and Crepeau patents, cited above, are applicable to outdrives of inboard/outboard motors or outboards where the propeller itself is either able to be raised out of the water or otherwise is readily accessible. However, they are not suitable for propellers for inboard engines in which the propeller is typically several feet (or more) below the surface of the water. These designs, if adapted for such a propeller, would require a diver to disengage the cover from the propeller. None of the designs of the prior art address the problems of fouling of propellers of larger vessels in which the propeller is submerged substantially below the waterline, or provide an effective protective system for such a vessel which can be readily released by the user from a position on deck, without requiring the services of a diver. 
     SUMMARY 
     In one aspect, an underwater protective system for installation on the propeller of a boat is provided. The system is designed to inhibit marine growth on the propeller. The system includes a flexible material sized and shaped so as to be capable of being wrapped around the front and rear surfaces of the blades of a propeller and gathered so as to substantially surround the propeller. A fastening member, e.g., clamp, clip, snap, Velcro®, or other fastening device, is affixed to the flexible material and is used for maintaining the flexible material in the gathered state, e.g., by clamping the flexible material about the propeller. The system further includes a link (such a piece of line, webbing or a wand) having one end attached to at least one of the fastening member and the flexible material. The link is of sufficient length such that when the flexible material is gathered about the propeller and maintained in place with the fastening member, the link extends to a location proximate to the boat at or above the waterline of the boat (such as to the transom or deck of the boat, or to a dock against which the boat is tied) wherein the link can be retrieved by a user of the boat. The link and fastening member are constructed and arranged wherein a tug on the link by the user releases the gathered flexible material from the propeller, permitting the retrieval of the line, and the fastening member and the flexible material as a unit from the propeller for later reuse or disposal without requiring the aid of a diver. 
     In another aspect, a method of inhibiting marine growth on a propeller of a boat is described. The method includes steps of: while the boat is in water, wrapping a flexible material around the front and rear surfaces of the blades of the propeller and gathering the material so that the material substantially surrounds the propeller; maintaining the flexible material in the gathered state with the aid of a fastening member; and leading a link having one end attached to at least one of the fastening member and the flexible material to a location at or above the waterline of the boat wherein the link can be retrieved by a user of the boat. The link and fastening member are constructed and arranged wherein a tug on the link by the user releases the gathered flexible material from the propeller permitting the retrieval of the link, and the fastening member and the flexible material as a unit from the propeller. 
     In another aspect, a kit is disclosed comprising a set of the underwater protective systems as recited above designed to fit different size propellers. For example, the kit may include a first portion in which the flexible material is relatively reduced surface area such that the material is designed to fit propellers having a diameter under 20 inches. A second portion of the kit includes flexible material of a larger surface area is designed to fit propellers having a diameter of at least 20 inches. A diver offers a service of fitting boats in a marina with the protective systems of this disclosure and will include in the kit a multitude of such underwater protective systems of different sizes to fit sailboats and smaller powerboats of various sizes and propeller diameters (e.g., 12 inch to 18 inch), pleasure power boats with larger size propellers (e.g., with propeller diameters from 16 to 36 inches), and larger commercial vessels (e.g., with propellers from 36 to say 50 inches in diameter). The diver (or customer/boat owner) may trim excess material from the flexible material to obtain a more customized fit of the protective material to the propeller, taking into consideration such factors as the number of blades to the propeller, and the diameter of the propeller. 
     The underwater protective devices of this disclosure may optionally include a second flexible material or cover adapted to surround an underwater component of the boat remote from the propeller (e.g., a depth transducer, knot wheel, etc.) and a second link extending from the second flexible material to a location at or above the waterline of the boat where the second link can be retrieved by the user. 
     In one configuration, the protective system is manufactured and sold as a unit comprising the flexible material, attached clamping member, and the link. Alternatively, the system is sold as the flexible material and the attached fastening member along with instructions for the purchaser to obtain a suitable length of line or webbing and attach one end to the fastening member and lead the other end to a convenient location above the water line such as the transom, deck, or nearby slip. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of the protective system of this disclosure installed on the propeller of a boat having an inboard engine, submerged several feet below the waterline of the boat, with the link extending into the cockpit of the boat.  FIG. 1  also shows a protective cover for an underwater component (e.g., depth transducer) and a second link extending from the protective cover for the component to the cockpit. 
         FIG. 2  is a detailed view of the flexible material of the protective system gathered about the propeller of  FIG. 1 , and clamped or otherwise held in place about the propeller with fastening member such as a clamp, clip or other device. 
         FIG. 3  is a further more detailed view of the clamp of  FIG. 2  and the first end of the link extending through the level arms of the clamp. 
         FIG. 4  is plan view of the protective system of  FIGS. 1-3  prior to installation on the propeller, showing a clamp affixed to the flexible material and the link. 
         FIG. 4A  shows the steps involved of installing the protective system of  FIG. 4  on a propeller. 
         FIG. 5  is a perspective view of the protective system of  FIG. 4 . 
         FIG. 6  is a more detailed view of one embodiment of the clamp of  FIGS. 1-5 . 
         FIG. 7  is an illustration of the protective system of this disclosure installed on the propeller of a fin-keel type sail boat. 
         FIG. 8  is an illustration of the protective system of this disclosure installed on a propeller of a commercial fishing boat. 
         FIGS. 9A-9C  are illustration of three embodiments of a protective system for an underwater component such as a depth transducer. 
         FIG. 10  is an alternative configuration for a protective cover made from a flexible material adapted to protect underwater components such a depth transducers from marine growth. 
     
    
    
     DETAILED DESCRIPTION 
     The protective system of this disclosure is designed to prevent or inhibit marine growth from attaching to propellers of vessels. The protective system is particularly useful for propellers of inboard engines of marine vessels of all types, in which the propeller is both fixed and submerged substantially below the waterline of the vessel and therefore relatively inaccessible from above the water (e.g., from a dinghy, a dock or the transom of the vessel). It could also be used on inboard-outboard propellers or outboards that are not adapted to pivot out of the water. 
     The protective system includes a flexible material that is gathered about the propeller and clamped in place with a fastening member, such as a clamp, Velcro™, snaps, clip, a pin, a hook, a slip knot, or other suitable fastening device. In preferred embodiments the fastening member is made from a plastic or other material which contains no metal. A link, e.g., length of light line, webbing or a rigid strut or wand such as a piece of wood, has one end which is attached to the fastening member and/or the flexible material and a second free end which is led to a position above the waterline of the vessel where it can be readily retrieved by the user of the boat. When the user is ready to remove the protective system, they give a tug on the link and that action releases the gathering of the flexible material, allowing the fastening member and flexible material to be removed as a unit from the propeller and retrieved for later re-use, cleaning or disposal. 
     The flexible material serves to inhibit marine growth in at least two ways. First, it provides a barrier preventing barnacle larvae from reaching the propeller. Secondly, it shades the propeller from the sun thereby inhibiting growth of grass or slime on the blades of the propeller. The flexible material need not be wrapped perfectly tightly about the propeller, and indeed a loose fitting of the flexible material about the propeller is sufficient and promotes easy and reliable release of the protective system by the user from a position above the waterline. 
     For most boats, the system of this disclosure is typically installed on the propeller by a diver (which could be the owner if they are willing to get wet or have suitable dive equipment). However, a diver is not needed to remove the protective system. It can be immediately removed by simply pulling on the link. 
     The protective system will now be described with reference to the appended Figures, which show representative and non-limiting examples of how the protective system can be constructed and installed on a variety of vessels. 
       FIG. 1  is a schematic illustration of a protective system  10  installed on the propeller  12  of a boat  14  having an inboard engine (not shown), in which the propeller is submerged several feet below the waterline  16  of the boat  14 . The protective system includes a flexible material  20  which is gathered around and about the front and rear surfaces of the propeller  12 . A fastening member, which in one preferred embodiment is a clamp  22  (see  FIGS. 3-6 ) is attached or affixed to the flexible material  20  and clamps the material so that the material is maintained in the gathered condition. The fastening member is preferably metal-free (e.g., made of a plastic or fiberglass material) so as to avoid corrosion in a salt water environment. A link  24  (e.g., line or webbing) has one end thereof  26  ( FIG. 3 ,  4 ) attached to the clamp  22  and a free second end  26 . The link  24  is of sufficient length such that when the flexible material  20  is gathered about the propeller  12  and clamped with the fastening member (clamp  22 ), the free end  26  of the link  24  extends to a location proximate to the boat at or above the waterline of the boat wherein the link can be retrieved by a user of the boat, e.g., in the cockpit of the boat as shown in  FIG. 1  or tied to a slip adjacent to the boat. 
     To remove the protective system, the user grasps the free end  26  of the link  24  and gives it at tug. This action releases the material  20  from the clamp  22 . By pulling in on the link  24  the user then retrieves the material  20  and clamp  22  as a unit from the propeller and brings it on deck for cleaning and stowage or disposal. This action is done by the user from the cockpit or the adjacent slip, without the user getting wet. No diver is required to remove the protective system  10 . 
     In an embodiment in which the fastening member  22  is in the form of snaps or Velcro, for example, the invention works in a similar fashion. The fastening member is sufficient to hold the flexible material gathered around the propeller. The end of the link may be attached to the fastening member, or alternatively it may be attached to the flexible material directly. 
       FIG. 1  also shows a second protective cover  30  for an underwater component (e.g., depth transducer  32 ) and a second link  34  extending from the protective cover  30  such that the free end  36  is in the cockpit, on deck or tied to an adjacent slip. This embodiment may optionally use an elastic band to retain the cover  30  on the fitting  32 , or the cover may be secured by means of gathering the material forming the cover about the fitting and clamping it in place with a clamp, in which case the end of the link  34  is attached to the clamp. In either situation, the cover is removed by the user simply by tugging on the link  34  and pulling the cover into the cockpit for cleaning and stowage or for disposal. 
       FIG. 2  is a more detailed view of the flexible material  20  of the protective system  10  gathered about the blades  12 A,  12 B and  12 C of the propeller  12  of  FIG. 1 , and maintained in place with the clamp  22  or other suitable fastening member such as a clip or snaps. The manner or technique by which the material  20  is gathered about the blades of the propeller and maintained in place so that the material surrounds both the front and rear surfaces of the propeller is not critical. The material can be gathered on the side of the propeller proximate to the propeller shaft, outboard of the propeller (where a zinc anode would be typically placed for a boat immersed in salt water), proximate to one of the blades, or between the blades. The point of gathering can be on the “top” of the propeller (i.e., the point closest to the water surface), or to the side or even on the “bottom” of the propeller. In  FIG. 2  the gathering is indicated by the folds or creases  40  in the material. 
       FIG. 3  is a further more detailed view of the clamp  22  of  FIG. 2  and the first end  26  of the link  24 . In this embodiment, the clamp  22  takes the form of a C-shaped clamp (a clamp or clip of this type for paper is suitable) having a spring-like clamping element  50  and pairs of lever arms  52  attached to the clamping element  50  that are used to expand the C-shaped clamping element to allow the clamp to fasten to the gathered material, whereupon the lever arms are released. The end  26  of the link  24  is led through the lever arms  52  and tied in a knot (e.g., bowline). When the link  24  is pulled, this action pulls the clamp  22  off of the gathered material held by the clamp. The material  20  then can be pulled free from the propeller. Thus, hauling in the link  24  allows the clamp  22  and attached material  20  to be removed as a unit from the propeller and retrieved for cleaning and later re-use, or for disposal. 
     Suitable materials from the flexible material  20  include plastic sheeting, canvas, Sunbrella and other synthetic fabrics, as well as materials specifically adapted for receiving antifouling paints such as Hypalon (chlorosulfonated polyethylene synthetic rubber), Hypalon coated nylon, and PVC-coated nylon. In one embodiment, the flexible material is coated with antifouling paint. 
       FIG. 4  is a plan view of the protective system of  FIGS. 1-3  prior to installation on the propeller of  FIG. 1 .  FIG. 5  shows the system in a perspective view. The flexible material includes two rectangular panels  60  and  62  of approximately the same size, with two adjacent edges joined by a seam as indicated at  64  and  66  and having open sides  68  and  70 , forming a quasi tent-like structure. At one corner of the material  20  a clamp  22  is attached to both panels  60  and  62 . In the example of the paper clip-like C-clamp  22  as shown in  FIG. 6 , the clamp  22  is disassembled, four holes are made in the material (two on each panel  60  and  62 ) and then the free ends  70  and  72  of the lever arms are inserted into the holes and then assembled into the corresponding receiving structures  74  and  76  of the clamp  22 . In this manner, the lever arms  52  protrude from the exterior surface of the material  20  but the clamping element is on the inside of the panels  60  and  62  as shown by dashed lines in  FIG. 4 . The end  26  of the link  24  is tied off to one, or more preferably both, of the lever arms  52  and the length of the link  24  trimmed so that it has sufficient length to extend from the propeller to a convenient position above the waterline, e.g., to the deck or cockpit of the boat or a slip adjacent to the boat. 
     The length L ( FIG. 5 ) and the width W of the panels  60  and  62  will of course vary depending on the size of the propeller that the system is going to be installed on. For example, for a three-blade propeller of 16 inches in diameter the panels may have a length L of 30-40 inches and a width W of 12-16 inches. 
     It will be noted that while in the embodiment of  FIG. 4  the two panels  60  and  62  are joined by seams  64  and  66 , this is not essential, and a single rectangular panel of material can be folded in half length-wise and only seam  64  added to join one edge to form the structure of  FIG. 4 . Still other configurations for the flexible material are possible, including oval or circular shapes. Continuous, bag-like shapes are less preferred since they would be difficult to remove without the aid of a diver. However, such shapes might be used if provisions are made for extraction of the material without difficulty, such as providing slits in the material, or gathering the material and clamping it at several locations, with each location being provided with an attached clamp  22  and associated retrieval link  24 . 
       FIG. 4A  shows the installation of the protective system on a propeller  12 . The cover  20  is installed over one of the blades  12 A so that the blade is placed within the two panels  60  and  21  as shown in the upper view. The user then essentially wraps or gathers the material  20  about the other two blades as indicated by the arrows so that they are placed within the panels  60  and  62  and the edge  68  is brought around to the edge  64  to thereby wrap up the propeller as shown in the lower view. The fastening member  22  is then affixed to the material (typically where the edges  64  and  68  meet) to maintain the flexible material  20  in the gathered state. The fastening member is shown as a ratchet-type clamp in  FIG. 4A . The free end of the link  24  is tied to one or both of the arms of the fastening member  22 . The fastening member is attached to the flexible material  20  in any suitable manner. When the user pulls the link  24 , the jaws of the fastening member release from the material  20  and allow the material  20 , fastening member  22  and link  24  to be retrieved for later reuse or disposal. 
     As noted above, the protective system of this disclosure is suitable for use with a variety of different configurations of propellers and different boats.  FIG. 7  is an illustration of the protective system  10  of this disclosure installed on the propeller of a fin-keel type sail boat.  FIG. 8  is an illustration of the protective system of this disclosure installed on a propeller of a deep draft commercial fishing boat having a four bladed propeller five or six feet below the water line. 
       FIG. 9A  shows the protective cover for an underwater component such as a depth transducer in the form of a flexible material  30  ( FIG. 1 ) in the form of a pouch or bag having an elastic band  80  about its rim to hold onto the component and prevent it from falling off. The link  34  (line or webbing) is lead to a position on the deck of the boat as shown in  FIG. 1 . The link has one end thereof fastened to a fastening member such as a ring  22 .  FIG. 9B  shows an alternative embodiment with the ring  22  located in the middle of a bottom panel of the cover.  FIG. 9C  shows another embodiment in which the bottom panel includes a solid reinforcement  32  to prevent barnacle larvae from penetrating the cover and the fastening member is in the form of two holes/grommets  35  formed in the cover  30 . The user leads the link through the holes  35  and ties off the end of the link in a knot. In  FIG. 10 , the cover  30  is in the form of a rectangular or irregular shaped material having a clamp  22 A or other suitable fastening member attached to the material  30  (as described above for  FIG. 4 ), and a line  34  tied off to the lever arms of the clamp and lead to a position on deck or in the cockpit. In the embodiments of  FIGS. 9 and 10 , the user tugs on the free end of the link  34  from the convenience of the deck or cockpit to remove the cover  30  from the underwater metal fitting. The link  34  is preferably tied to the bottom or corner of the cover  30  so that it will release when pulled from above. 
     While the link  24  is shown in the Figures as a length of line, it could also take the form of webbing or a rigid member, e.g., a wood, plastic or fiberglass wand. One end of the rigid member is tied or otherwise affixed to the clamp and the free end led or tied off at the transom or adjacent slip. 
     In one configuration, the protective system is manufactured and sold as a unit comprising the flexible material, attached clamping member, and the link. Alternatively, the system is sold as the flexible material and the attached fastening member along with printed instructions for the purchaser to obtain a suitable length of line or webbing and attach one end to the fastening member and or flexible material and lead the other end to a convenient location above the water line such as the transom, deck, or nearby slip. 
     The following clauses are offered as further descriptions of the disclosed invention. 
     1. A protective system for underwater installation on the propeller  12  of a boat, the boat having a waterline, the propeller having blades with front and rear surfaces, comprising: 
     a flexible material  20  sized and shaped so as to be capable of being wrapped around the front and rear surfaces of the blades of the propeller and gathered so as to substantially surround propeller; 
     a fastening member  22  (e.g., clamp, clip, Velcro™, snaps, pin, or other suitable fastener) affixed to the flexible material ( FIG. 4 ) for maintaining the flexible material in the gathered state (as shown in  FIGS. 2 and 3 ); and 
     a link  24  having one end attached to at least one of the fastening member and the flexible material, the link having sufficient length such that when the flexible material is gathered about the propeller and maintained in place with the fastening member, the link extends to a location proximate to the boat at or above the waterline of the boat (e.g., the deck, transom or cockpit) wherein the link can be retrieved by a user of the boat; 
     wherein the link and fastening member are constructed and arranged ( FIGS. 1-8 ) wherein a tug on the link by the user releases gathered flexible material from the propeller permitting the retrieval of the link, and the attached fastening member and the flexible material as a unit from the propeller without the aid of a diver. 
     2. The system of clause 1, wherein the link  24  comprises a flexible line and wherein the flexible line is of sufficient length to extend from the fastening member to a position on the deck of the boat ( FIG. 1 ,  7 ,  8 ). 
     3. The system of clause 1, wherein the link  24  comprises a length of webbing and wherein the webbing is of sufficient length to extend from the flexible material to a position on the deck of the boat. 
     4. The system of clause 1, wherein the link comprises a rigid member (e.g. wood, plastic or fiberglass) of sufficient length to extend from the flexible material to a position substantially above the waterline of the boat. 
     5. The system of clause 1, wherein the flexible material  20  comprises a material specifically designed and suited for application of antifouling paint (e.g., Hypalon). 
     6. The system of clause 1, further comprising antifouling paint applied to the flexible material. 
     7. The system of clause 1, wherein the flexible material comprises first and second opposed rectangular panels  60 ,  62  of material each and first and second adjacent edges ( FIG. 4 ), the first and second adjacent edges being joined together; and 
     wherein the first and second rectangular panels comprises a corner portion and wherein the fastening member is affixed to the corner portion ( FIG. 4 ). 
     8. The system of clause 1, wherein the fastening member comprises a C-shaped clamp ( FIG. 6 ) having first and second levers extending therefrom which operate to open the clamp, and wherein the link is attached to one or both of the first and second levers ( FIGS. 3 ,  4 ,  5 ). 
     9. A method of inhibiting marine growth on a propeller of a boat, the boat having a waterline, the propeller having blades with front and rear surfaces, comprising: 
     while the boat is in water, wrapping a flexible material  20  around the front and rear surfaces of the blades of the propeller and gathering the material so that the material substantially surrounds the propeller; 
     maintaining the flexible material in a gathered state with the aid of a fastening member  22  affixed to the flexible material ( FIG. 4 ); 
     leading a link  24  having one end attached to at least one of the fastening member and the flexible material to a location at or above the waterline of the boat wherein the link can be retrieved by a user of the boat ( FIGS. 1 ,  7 ,  8 ); 
     wherein the link and fastening member are constructed and arranged wherein a tug on the link by the user releases gathered flexible material from the propeller permitting the retrieval of the line, and the fastening member and attached flexible material as a unit from the propeller without the aid of a diver. 
     10. The method of clause 9, wherein the link comprises a flexible line and wherein the flexible line is led to a position above the waterline of the boat. 
     11. The method of clause 9, wherein the link comprises a length of webbing and wherein the webbing is led to a position above the waterline of the boat. 
     12. The method of clause 9, wherein the link comprises a rigid member and wherein the rigid member is led to a position substantially above the waterline of the boat. 
     13. The method of clause 9, wherein the flexible material comprises a material specifically designed and suited for application of antifouling paint. 
     14. The method of clause 9, wherein the maintaining step comprises clamping the flexible material with a C-shaped clamp having first and second levers extending therefrom which operate to open the clamp ( FIG. 6 ), and wherein the link is attached to one or both of the first and second levers ( FIG. 3 ,  4 ). 
     15. The method of clause 9, wherein the wrapping, maintaining and leading steps are performed by a diver. 
     16. A kit comprising a set of the underwater protective systems as recited in claim  1  constructed to fit different size propellers. 
     17. The kit of clause 16, wherein a first portion of the kit is designed to fit propellers having a diameter under 20 inches and second portion of the kit is designed to fit propellers having a diameter of at least 20 inches. 
     18. A protective system comprising a flexible material  30  adapted to surround an underwater component remote from the propeller ( FIG. 9 ) and a link  34  extending from the flexible material to a location at or above the waterline of the boat where the link can be retrieved by a user. 
     19. The apparatus of clause 18, wherein the flexible material further comprises a clamp affixed to the flexible material and wherein the link is a attached to the clamp ( FIG. 10 ). 
     20. The apparatus of clause 18, wherein the flexible material further comprises a rim and an elastomeric band in the rim enabling the flexible material to snugly envelop the component ( FIG. 9A ). 
     21. A protective system for underwater installation on the propeller  12  of a boat, the boat having a waterline, the propeller having two or more blades each having front and rear surfaces, comprising: 
     a flexible material  20  sized and shaped so as to be capable of being wrapped around the front and rear surfaces of the blades of the propeller and gathered so as to substantially surround propeller; 
     a fastening member  22  (e.g., clamp, clip, Velcro™, snaps, or other suitable fastener) affixed to the flexible material ( FIG. 4 ) for maintaining the flexible material in the gathered state (as shown in  FIGS. 2 and 3 ); and 
     instructions for a user to attach one end of a link  24  to at least one of the fastening member and the flexible material, the link having sufficient length such that when the flexible material is gathered about the propeller and maintained in place with the fastening member, the link extends to a location proximate to the boat at or above the waterline of the boat (e.g., the deck, transom or cockpit) wherein the link can be retrieved by a user of the boat whereby a tug on the link by the user releases the gathered flexible material from the propeller permitting the retrieval of the link, and the attached fastening member and the flexible material as a unit from the propeller without the aid of a diver. 
     Various modifications to the illustrated embodiments may be made without departure from the spirit and scope of the invention. This true scope and spirit is to be arrived at by reference to the appended claims, interpreted in light of the foregoing specification.