To replace a 16 horsepower gas engine driving a snowblower at 1000 RPM with a hydraulic system, a hydraulic pump and motor must be selected based on power conservation principles. The required torque for the snowblower is calculated to be 1008 in.lb, and the pump should operate at approximately 3000 RPM. Efficiency is a critical factor, with an assumed efficiency of 0.85 affecting both the GPM and PSI for the pump and motor. The formulas provided can determine the necessary GPM and PSI to achieve the desired performance. Proper calculations ensure the hydraulic system matches the power and torque requirements of the original gas engine setup.