The main function of trolling motors was once to keep the boat running at a consistent, low speed suitable for trolling, but that function has been augmented by GPS-tracking trolling motors that function as "virtual anchors" to automatically maintain a boat's position relative to a desired location, such as a favorite fishing spot.
Trolling motors are often lifted from the water to reduce drag when the boat's primary engine is in operation.
An 1895 article in Scientific American entitled "A Portable Electric Propeller for Boats" stated: "Briefly described, it consists of a movable tube which is hinged at the stern of the boat, much as an oar is used in sculling.
This tube extends down and out into the water, where it carries a propeller, and at the inboard end an electric Motor is attached, which is itself driven by batteries."
Schmidt in 1934[3] in Fargo, North Dakota, when he took a starter motor from a Ford Model A, added a flexible shaft, and a propeller.