A motor, such as an internal combustion engine or an electric motor, drives two or more pumps, which pump fluid through a discharge system, and a speed measuring device is provided for producing a signal when the speed of the motor is reduced due to the load on the motor reaching a predetermined high value, short of an overload. Two or more pump discharge regulators are provided, one for each pump, cooperating with the measuring device to reduce the output of at least one of the pumps in response to a signal to thereby prevent overloading of the engine or motor.