This Pump works off oscillations generated by the engine. Oscillating pumps will also work on inverted or side-mounted engines. This pump can be used with ALCOHOL BASED FUELS ONLY This is the version called the "silver hex screw". Each time the engine fires, the pump reacts with a short rotation in the direction opposite of the propeller rotation. This will only work if the pump is mounted in line, with the arc of the prop and about 1.5" from the crankshaft centerline.