A programmable boatlift system having a cable extending up from one end of a boatlift cradle, across through a shaft attached to a motor, and down to an opposite end of the boatlift cradle. A position sensor having an idler sheave is placed on the cable, or a position sensor having a collar is placed on the shaft. The motor turns the shaft to cause the cable to move across the roller sheave, or to cause the collar to rotate, to raise or lower the boatlift cradle. The position sensor produces an output signal proportional to the distance the cable travels over the idler sheave or proportional to the number of rotations of the collar. An electronic control circuit uses the output signal to infer the vertical position of the boatlift cradle and to position the boatlift cradle as desired.