A boat propulsion system includes a plurality of positive displacement pumps which having high discharge head and having inlets and outlets therein and a controlling panel having circuits, wherein the pumps are mounted on a bottom of a boat and driven by a motive power. By means of different positions of the outlets in each pump or different power transmission of each pump and cooperating with using the controlling panel, the boat can therefore move toward desired directions and enhancing power transmission by the pumps are drawn uniform flow when the boat is moved.