Abstract: Speed controlling apparatus particularly is disclosed to be mounted with respect to a boat motor in a position confronting the propeller wash of the boat's motor, whereby the thrust imparted to the water by the motor's propeller is significantly deflected or attenuated, thus reducing boat speed. The contemplated speed controlling apparatus includes a mounting plate adapted to be mounted upon the motor housing, and a deflection or trolling plate coupled to said mounting plate to be disposable between a first position confronting the propeller wash, and a second position disposed remotely from the path of the propeller wash. In a first aspect of this invention, the deflection plate is variably disposed with respect to the path of the propeller wash and in particular, may be disposed at variable depths within the water.