Propeller security device

A boat propeller lock for boat propellers of the type that include a central shaft with a plurality of outward extending propeller blades, and that attach to the drive shaft of an outboard or inboard/outboard marine motor is provided. In one embodiment, the invention includes a generally U-shaped member consisting of a base member and a pair of parallel arms. A generally C-shaped member having a pair of parallel arms extending perpendicular to the C-shaped member, with one arm extending from each end of the "C" of the C-shaped member. The U-shaped member being adapted so the base member fits the front portion of an outboard or inboard/outboard lower unit with the parallel arms facing aft of the lower unit, and the C-shaped member being positioned over the rear of the marine propeller with the parallel arms facing forward. The parallel arms of the U-shaped member being slidably engagable with the parallel arms of the C-shaped member. One of the members includes a locking portion that permits slidable engagement of the parallel arms, but prevents disengagement thereof unless the locking portion is unlocked. At least one of the parallel arms can include a plurality of longitudinally spaced ratchet teeth. The lock portion can include a pawl adapted to engage the rachet teeth to permit the U- and C-shaped members to be slid together while preventing the members from being pulled apart when in the locked position.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to devices for preventing marine propellers attached 
to marine motors from being stolen when not in use. More particularly, the 
invention relates to devices that attach to the exterior of marine motors 
to lock the propeller to the motor preventing the unauthorized removal of 
the propeller. 
2. Description of Related Art 
Theft of boat propellers from marine motors when not in use is a problem 
for boat owners, marinas, insurance companies, and law enforcement 
authorities. The advanced design and materials of present day marine 
propellers creates a high value item that can be targeted for random and 
organized theft. Typically, propellers are bolted to marine outboard, or 
inboard/outboard, motor drive shafts and are left in place when the boat 
is not in use. When left unattended, the propellers can be removed simply 
by unbolting the propeller from the marine motor drive shaft. 
As known in the art, inboard/outboard motors refer to the type of marine 
propulsion in which the marine motor is housed within the boat hull and 
the drive unit is positioned on the outer stern of the boat. The lower 
drive unit for the inboard/outboard motor is substantially the same as the 
lower drive unit from an outboard motor. The drive shaft in which the 
propeller is attached refers to the propeller drive shaft which located in 
the lower drive unit of the outboard and inboard/outboard motors. 
What is needed is a quickly and easily installed lock that secures a marine 
propeller to the motor drive shaft to prevent unauthorized removal of the 
propeller. Because the lock should be in place protecting the propeller 
whenever the boat is not being used, the lock should have an attractive 
physical appearance. The lock should be easy to manufacture and low in 
cost. 
SUMMARY OF THE INVENTION 
The present invention provides a boat propeller lock for boat propellers of 
the type that include a central shaft with a plurality of outward 
extending propeller blades, and that attach to the propeller drive shaft 
of the lower drive unit of an outboard or inboard/outboard marine motor. 
In one embodiment, the invention includes a first, generally U-shaped, 
member consisting of a base member and a pair of parallel arms. A second, 
generally C-shaped member, having a pair of parallel arms extending 
perpendicular to the C-shaped member, with one arm extending from each end 
of the "C" of the C-shaped member. 
The parallel arms of the U-shaped member being slidably engagable with the 
parallel arms of the C-shaped member. One of the members includes a 
locking portion that permits slidable engagement of the parallel arms, but 
prevents disengagement thereof unless the locking portion is unlocked. 
In one embodiment, at least one of the parallel arms can include a 
plurality of longitudinally spaced ratchet teeth. The lock portion can 
include a pawl adapted to engage the rachet teeth to permit the U- and 
C-shaped members to be slid together while preventing the members from 
being pulled apart when in the locked position. The ratchet teeth can be 
covered by a longitudinally expandable flexible protective boot which 
expands over the teeth as the U- and C-shaped members are pulled apart. 
The locking portion of the present invention can be unlocked by key or by 
combination-type tumbler settings. The locking portion of the present 
invention can be similar to the locking devices disclosed in U.S. Pat. No. 
5,488,844, the disclosure of which is incorporated herein by reference. 
In operation, the generally U-shaped member is placed around the front 
portion of the lower drive unit of an outboard or an inboard/outboard 
marine motor with the parallel arms facing toward the aft end of the lower 
unit. The U-shaped member is placed in front of the drive shaft with the 
parallel arms extending somewhat parallel to the drive shaft. 
The generally C-shaped member is then placed circumferentially around the 
aft end of the shaft portion of an attached marine propeller behind the 
propeller blades, with the parallel arms of the C-shaped member facing 
forward and slidably engaging with the rear facing parallel arms of the 
U-shaped member. 
The C-shaped member is sized such the C-shape is larger in circumference 
than the shaft portion of the propeller with the ends of the C-shape 
extending beyond a diameter of the shaft portion. The forward facing 
parallel arms extend around, thus capturing, at least two propeller blades 
to ensure that the invention cannot be removed without unlocking the 
locking portion. The U- and C-shaped members are slid together until the 
C-shaped member is snugly against the front edge of the at least two 
propeller blades. The U- and C-shaped members will not be removable unless 
the locking portion is unlocked. 
Accordingly, it is an objective of the present invention to provide a 
marine propeller lock that is quickly and easily installed that securely 
locks the propeller to a marine motor drive shaft when not in use to 
prevent unauthorized removal of the propeller. 
It is a further objective of the present invention to provide a marine 
propeller lock that has an attractive physical appearance, and that is 
easy to manufacture. 
In accordance with these and other objects which will become apparent 
hereinafter, the instant invention will now be described with particular 
reference to the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention will now be described in detail utilizing one 
embodiment for example. 
Referring to FIG. 1, the present invention 10, includes a generally 
U-shaped member 2 having a base member 4, and a pair of parallel arms 6 
and 8. A generally C-shaped member 12 includes a pair of parallel arms 14 
and 16 which extend substantially perpendicular to the C-shaped member 12 
from the ends 15 and 17 of C-shaped member 12. 
The present invention 10 can be made of any material or combination of 
materials suitable for locks and which are difficult to break apart by 
unauthorized tampering. The materials are preferably metal, such as steel, 
case-hardened steel, aluminum, titanium, and alloys. Some of the 
components of the invention can be made of non-metallic composites. The 
base member 4 and pair of parallel arms 6 and 8 of generally U-shaped 
member 2 can be made of individual parts connected together in 
conventional manner, such as welded, or can be integrally constructed as 
one piece. The pair of parallel arms 14 and 16 can be connected to the 
generally C-shaped member 12 in conventional manner, such as welded near 
ends 15 and 17, or can be integrally constructed. 
The parallel arms 6 and 8 of U-shaped member 2 are slidably engagable with 
the parallel arms 14 and 16 of the C-shaped member 12. The ends of arms 14 
and 16, opposite the C-shaped member, can include shaft portions 18 and 
20. Arms 6 and 8 can include bores 22 and 24 sized to receive shafts 18 
and 20, respectively. 
Shaft 18 can include a plurality of longitudinally spaced ratchet teeth 26. 
Teeth 26 can extend partially around shaft 18, or can extend fully 
circumferentially around shaft 18. Lock 28 can include a conventional pawl 
adapted to engage rachet teeth 26 to permit U-shaped member 2 and C-shaped 
member 12 to be slid together while preventing the members from being 
pulled apart when lock portion 26 is locked. 
Lock 26 permits slidable engagement of shafts 18 and 20 into bores 22 and 
24, but prevents disengagement thereof unless lock 26 is unlocked. 
The ratchet teeth 26 can be covered by a longitudinally expandable flexible 
protective boot 27 which expands over the teeth 26 as U-shaped member 2 
and C-shaped member 12 are pulled apart. 
Lock 26 can be unlocked by key 29 or by combination-type tumbler settings, 
as known in the art. As discussed herein above, lock 26 can be similar to 
the locking devices disclosed in U.S. Pat. No. 5,488,844. 
Referring to FIG. 2, the generally U-shaped member 2 is placed around the 
front portion 30 of the lower drive unit 32 of an outboard or an 
inboard/outboard marine motor with the parallel arms 6 and 8 facing toward 
the aft end 34 of lower unit 32. U-shaped member 2 is placed in front of 
the lower unit 32 with parallel arms 6 and 8 extending substantially 
parallel to the drive shaft of lower unit 32. The drive shaft is not shown 
in FIG. 3, but the location of the drive shaft is well known in the art 
and is illustrated by the center line 35 of propeller 36. Propeller 36 is 
removably attached to the drive shaft, as known in the art. 
U-shaped member 2 includes V-bracket 38 which is sized to provide a secure 
and stable fit of member 2 against a plurality of front portions 30 of 
various sized lower units 32. 
Generally C-shaped member 12 is then placed circumferentially around the 
aft end 40 of the shaft portion 42 of an attached marine propeller 36 
behind the propeller blades 44, with the parallel arms 14 and 16 facing 
forward. Shafts 18 and 20 slidably engage with bores 22 and 24 of the rear 
facing parallel arms 6 and 8, respectively. 
C-shaped member 12 is sized such the C-shape is larger in circumference 
than the shaft portion 42 of propeller 36 with ends 15 and 17 extending 
beyond a diameter of shaft portion 42. The forward facing parallel arms 14 
and 16 thus extend around, or capture, at least two propeller blades 44 to 
ensure that the invention cannot be removed without unlocking lock 28. 
Members 12 and 2 are slid together until C-shaped member 12 is snugly 
against the aft edge of the at least two propeller blades 44. U-shaped 
member 2 and C-shaped member 12 will not be removable unless the lock 28 
is unlocked. 
Hence, with the present invention 10 in place, propeller 36 cannot be 
removed from lower unit 32 by unauthorized methods. 
Propeller 36 is illustrated with three propeller blades 44, but can be a 
propeller having at least two and up to any number of blades 44. The 
invention 10 can be adapted to fit over a propeller 36 having any number 
of blades 44. 
The exterior surface of the exposed portions of invention 10 can be coated 
with a plastisol layer to protect the finish of the lower unit 32 and the 
propeller 36 from marring, and to give invention 10 an attractive 
appearance. 
The example provide herein above can include variations and modifications 
within the scope of the invention. For example, the ratchet teeth 26 can 
be utilized on either shaft 18 or 20, or both. The shafts 18 and 20 and 
bores 22 and 24 can be reversed such that member 2 would include shafts 18 
and 20, and member 12 would include bores 22 and 24. Alternately one shaft 
and one bore could be included on each of members 2 and 12. 
In addition, the U-shaped member 2 and C-shaped member 12 could be formed 
into alternate shapes. For example, member 2 could be C-shaped, and member 
12 could be U-shaped. Member 12 could be D-shaped and member 2 could be 
V-shaped. 
The instant invention has been shown and described herein in what is 
considered to be the most practical and preferred embodiment. It is 
recognized, however, that departures may be made therefrom within the 
scope of the invention and that obvious modifications will occur to a 
person skilled in the art.