Power generating apparatus includes a float mounted on a support pivotally mounted to a base and secured to a beam extending rearwardly of the base to a vertically extending elongated structure carrying a pair of vertically movable gear racks in guideways. Each rack is engaged by a gear wheel driven by movement of the racks and a one-way drive arrangement connects each gear wheel to an output shaft. Driving weights are secured to each rack to drive the racks in opposite directions under the action of gravity forces acting on the weights, thus causing the output shaft to rotate in a given direction. The free end of the beam is connected to a cross-arm vertically moveable on a guide on the elongate structure, the cross-arm having a motion transmitting arrangement to raise each weight during vertical movement of the cross-arm resulting from movement of the float.