Variable-displacement hydraulic motor comprising a shaft, an eccentric cam and an apparatus for controlling the position of the eccentric cam which comprises: - a means for moving the eccentric cam, comprising a double-acting cylinder acting via a piston on the eccentric cam for changing the eccentricity thereof and therefore the motor displacement of the motor; - an actuating unit for actuating the eccentric cam, comprising an electrovalve having two outputs (110a,110b) respectively connected to an associated chamber (350a,350b) of the double-acting cylinder, and a hydraulic control circuit (120a, 120b) for controlling the means for moving the eccentric cam, arranged between the outputs (110a,110b) of the electrovalve and the double-acting cylinder; - a control and command unit, which is feedback-connected between points for detecting one or more existing operating parameters (320a,320b,320c) of the motor and points for entering set values (250a,250b,250c) for the one or more operating parameters of the motor and which is designed to control operation of the actuating unit for actuating the eccentric cam wherein said electrovalve is of the direct-control type that is always fully open when activated and is driven by pulses having a predefined period with opening/closing time intervals of variable duration emitted by the control and command unit depending on the difference between a detected existing value (320,320b,320c) and a desired stored value (250a,250b,250c) of one of said parameters, and in that the hydraulic control circuit (120a, 120b) comprises stop valves (122a,122b) for stopping the actuating fluid that remain shut when the electrovalve is not excited for opening, locking the eccentric cam in position between one excitation and the other of the electrovalve. - a means for moving the eccentric cam, comprising a double-acting cylinder acting via a piston on the eccentric cam for changing the eccentricity thereof and therefore the motor displacement of the motor; - an actuating unit for actuating the eccentric cam, comprising an electrovalve having two outputs (110a,110b) respectively connected to an associated chamber (350a,350b) of the double-acting cylinder, and a hydraulic control circuit (120a, 120b) for controlling the means for moving the eccentric cam, arranged between the outputs (110a,110b) of the electrovalve and the double-acting cylinder; - a control and command unit, which is feedback-connected between points for detecting one or more existing operating parameters (320a,320b,320c) of the motor and points for entering set values (250a,250b,250c) for the one or more operating parameters of the motor and which is designed to control operation of the actuating unit for actuating the eccentric cam wherein said electrovalve is of the direct-control type that is always fully open when activated and is driven by pulses having a predefined period with opening/closing time intervals of variable duration emitted by the control and command unit depending on the difference between a detected existing value (320,320b,320c) and a desired stored value (250a,250b,250c) of one of said parameters, and in that the hydraulic control circuit (120a, 120b) comprises stop valves (122a,122b) for stopping the actuating fluid that remain shut when the electrovalve is not excited for opening, locking the eccentric cam in position between one excitation and the other of the electrovalve.