An apparatus which selectively increases the size of the wake of a boat with an outboard or sterndrive motor system. The apparatus has one or more plates attached to the boat hull which, when rotated below the bottom of the hull, extend into the flow of water when underway, increasing the size of the wake due to the dynamic displacement of water. A support bar mechanism transmits propulsive force from the motor drive unit to the plates to overcome resistive hydraulic loads. Linkages may be used to locate the support bar mechanism. In one embodiment, the support bar mechanism is comprised of a plurality of members and pivots such that the support bar mechanism can be stowed substantially out of the flow of water until larger wakes are desired. In other embodiments, mechanical cable, fluidic, or electrical control systems are used to control the configuration of the support bar mechanism.