What Shaft Length Do I Need to Look for to Fit an Electric Trolling Motor on My Boat?

For a transom (rear) mounted trolling motor location, measure from the top of the transom where the motor will be clamped to the water line. By adding 20 inches to this measurement, you will have the recommended size. For example, if the distance from the top of the transom to the water line is 15 inches, adding 20 inches gives a shaft length of 35 inches. Usual shaft sizes are 30, 36, and 42, so in this example, the 36-inch shaft would be the recommended choice.

To mount the motor on the bow (front) of the boat, measure from the mounting surface to the water line. For distances up to 22 inches, add 20 to obtain the recommended shaft length. For measurements of 22 to 28 inches, the recommended shaft length is 45 to 52 inches. For measurements of 28 to 34 inches, a shaft length of 54 to 62 inches is recommended. It is better to have the shaft slightly longer than too short; the shaft can be slid up or down in the mount for adjustment. If the shaft is too short, the motor will be lifted out of the water as the bow encounters waves and the prop will over-rev, splashing and making noise.

 *Measurements are made down from the mounting surface to the water line.