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The Leash, labeled image.

Mercury’s efforts preceded The Leash by nearly 50 years.

This post is best viewed on a laptop or desktop computer.

This post in no way belittles the development of or the accomplishments of The Leash, it just points out the basics of the concept have been around a long time. It also points out that one outboard manufacturer not only condoned the use of tethers, they factory installed them on tens of thousands of motors.

Back on January 12, 1967, Brunswick Corporation filed two patent applications that were later issued as the patents listed below:

• U.S. Patent 3,434,448 Combined Impact Damping and Power Lift Mechanism for an Outboard Propulsion Unit Assembly invented by W.L. Woodfill issued 25 March 1969, assigned to Brunswick Corporation (parent company of Mercury Marine).
• U.S. Patent 3,434,450 Mounting Arrangement for Hydraulic Impact Damping and Power Lift Means for an Outboard Propulsion Unit invented by well known Mercury engineer, D.F. (Dan) McCormick issued 25 March 1969, assigned to Brunswick Corporation (parent company of Mercury Marine).

The first patent teaches how to combine the damping needed to stop an outboard motor swinging up after striking a submerged object, with the power lift system as seen on the “Tower of Power”, the tall large horsepower Mercury outboards.

The second patent focuses more on the mounting arrangement used to accomplish the first patent.

We do find it a bit odd these two relatively complex patents list two separate inventors vs. listing them as co-inventors on each patent. They even share the same drawings. The first patent focuses more on the tether and specifically includes it as a claim in the patent.

Mercury’s tether is a heavy nylon strap about 1.75 inches wide and about one to two feet long (they come in different lengths depending on the outboard model and model year).

The tethers have a loop on both ends allowing them to be slipped over a metal rod.

In operation on the tower of power outboards, one looped end of the tether slips onto a rod on the swivel bracket (note a tube allowing the tether to swivel more easily is slipped over the rod first, then the looped end of the tether is slipped over the tube). The strap then loops around a metal bar on the outboard mounting bracket structure that is firmly attached to the transom, then the remaining looped end slides over the same rod on the swivel bracket that the first loop slipped on. See photos near the bottom of this post for how Mercury’s tether is assembled. The swivel bracket is tethered to the transom, just like The Leash.

The tilt cylinder(s) use external relief valves and check valves to allow the cylinder rod to collapse during collision with a submerged object which allows the swivel bracket to swing up with the rest of the outboard. Read More →