The prime mover provides movement, which gives the hydraulic system power. The prime mover can be a gas engine, diesel engine, or electric motor. The shaft of the engine or motor is connected to a hydraulic pump using a jaw coupler and mounting bracket. When selecting the appropriate prime mover, the important considerations are: Environment (access to a power source) Horse power (HP) Mounting style (tank mounted, or frame mounted) The more horse power your engine can produce, the more flow (GPM) and pressure your pump can produce. Flow is related to RPM, and HP is directly related to pressure (PSI). If your system doesn?t have easy access to electrical power, a gas or diesel unit may be necessary. If your application requires your prime mover to fit in a small space, then a tank mounted electric motor could be an option.