I answered my own question.
Gurdy Drive Systems
Trolling gurdies are the smallish reels used to wind trolling line in and out. While each gurdy has a clutch lever to engage and disengage its reel from the central shaft, the shafts can be driven however the boat owner likes.
According to the California Fisheries history, power driven gurdies weren’t common until the late 1940s; hand-hauled lines were used before that, which sounds like hard work.
Mechanical power was taken off the engine or prop shaft with a chain drive. Using the prop shaft would allow the drive to be reversed, or at least clutched, via the Hicks engine clutch gear.
An automobile transmission, without its clutch, could be used in the gurdy drive to reverse the drive, and change hauling speeds if desired. Any transmission could be used, but the Ford Model A was probably easily found.
(See Green boat)
Modern boats abandon the complication of mechanical drives for more flexible hydraulics. A hydraulic pump is mounted on the engine, and a hydraulic motor and control valve are mounted on the gurdies. Power and direction are easily controlled with the valve handle, independent of the engine. Theresa Ann, Santa Barbara, 2015; P. Matthews photo.