Prop Guard is made to surround the propeller like a nozzle. This designed nozzle action moves water with a controlled directional force which gives the boat improved handling and more power. This nozzle action is accomplished with no moving parts to adjust or replace. Whether you have an outboard or stern drive, Prop Guard will increase propeller efficiency, decrease fuel consumption and improve boat handling while reducing hull and engine stress. Technical testing of the Prop GuardR has proven that the performance of pleasure crafts are actually enhanced by the installation of the Prop Guard.