Abstract: A drive unit has an engine, an operatively connected driveshaft, a transmission, and a propeller shaft connected to a rotor outside a gear case. A plate, extending above the rotor, is adapted to slidingly receive along a joint axis, an accessory having an accessory joint element which is one of a channel and a protrusion. Extending parallel to the joint axis along a plate joint surface, which is one of a first surface facing away from the rotor and a second surface facing toward the rotor, is a plate joint element, which is the other of the channel and the protrusion, adapted to slidingly interlock with the accessory joint element to thereby prevent displacement thereof in a first direction parallel to the plate joint surface and perpendicular to the joint axis, and in a second direction normal to the plate joint surface. An accessory attachment method is also disclosed.