Abstract: A pair of lifting planes are secured to the hull of a boat on opposite sides of the keel. The lifting planes intersect the bottom surfaces of the hull at lines oriented generally along side the keel. The lifting planes have swept back leading edges and a span generally reaching to the chines. The outboard portions of said lifting planes are located at or adjacent to the longitudinal location of the center of gravity of the boat. The longitudinal location of the lifting planes is such that the resulting lifting force generated by the lifting planes at planing speeds acts adjacent to the center of gravity of the boat.

Abstract: A laterally extending trim vane is mounted for rotation about a horizontal axis on a submerged portion of a stern-drive propulsion unit housing, substantially within the slipstream of the propeller.The trim vane is mounted on structure which depends downwardly from a rearward part of a horizontally elongated intermediate portion of the housing. The aft location of the trim vane provides a relatively large moment arm for the vertical trim force. Hence, for a given moment, the aft position requires less force. Also, the propeller slipstream velocity relative to the vane is considerably higher than the speed of the boat. The aft location of the vane, providing the longer moment arm, and the utilization of slipstream water, providing a relatively high velocity of motive fluid, make it possible to make the control surface of the vane quite small.