An apparatus and method for mixing and delivering plural liquid components in a selected volume ratio. For each component, a separate motor drives a separate rotary gear pump that delivers the component to a common mixing and delivery device (spray gun). The speed of each motor, and correspondingly the volume of fluid delivered by that pump, is determined by a respective programmable computer. The individual computers are interlinked, with one master computer and the rest slave(s). Desired motor speeds are input into the computers in a selected ratio. A change in the speed of the master motor therefore produces a corresponding change in the speed of a slave motor according to the ratio. Actual motor speed is monitored and transmitted to the respective computer for feedback control. A simple manual ratio test is provided for calibration of the system. Each pump is magnetically coupled to its respective motor drive shaft.