Abstract: An engine includes a liquid reservoir and a wheel mounted for rotation about a central shaft. Float members are supported symmetrically about the wheel for rotational movement and for movement toward or away from the central shaft. Each float member is coupled with a diametrically opposed float member on an opposite side of the wheel by a connecting rod. A camming surface urges passing float members toward the central shaft, and simultaneously urges a diametrically opposed float member away from the central shaft. The wheel rotates as a result of an imbalance in the buoyant forces created by the float members. Magnetic forces can supplement the camming surface for moving the float members toward and away from the central shaft.