The distance between the boat deck and waterline will change depending on how much weight you have in the boat, so try to measure when you have all of your equipment with you.
When the propeller breaks the surface, it causes “cavitation,” which is when the propeller makes a loud noise when it slaps the water’s surface and makes loud noises that scare fish.
It’s okay for a trolling motor to be a little shorter if you’re mounting it to the transom since most boats have rear seats or a bench you can sit on while you steer.
If you need to make a small adjustment to the depth after you mount your trolling motor, loosen the depth collar knob on the top of the shaft until it slides freely. Then, pull or push the shaft so the propeller is 12 in (30 cm) below the surface before tightening the knob again. [8] X Research source
