"Marty S." wrote in message
...
Just a quick question... what is the proper depth of a transom mounted
electric trolling motor for the best efficiency in the water?

Mounting it deeper will result in more shaft dragging in the water and more
flex in the shaft (which will cause the motor angle to change, reducing
efficiency).

The shallower the motor is the more cavitation will result. Minor cavitation
will have a small impact on efficiency, and will greatly increase the
propeller noise (only an issue if you are trying to be quiet for fishing
purposes). If it is too shallow, it could even suck air from the surface,
which would have a dramatic impact on performance.

For low speeds, the interference from the hull of the boat will be minimal.
As the speed increases, the flow of water from the hull could create eddy
currents around the transom, which if the motor was too shallow could cause
additional cavitation.

Basically, I would recommend mounting it so that the top of the prop is a
couple of inches below the bottom of the boat. Any deeper and it creates
unnecessary draft concerns, any shallower and the prop may hit the bottom of
the boat if you spin the motor too far around.

Rod