Abstract: The instant invention is directed toward a marine craft having a semi-enclosed surfacing type propeller in a tunnel that draws air through specific areas located and shaped to enhance performance and compensate for prime mover torque and horsepower characteristics. The invention further relates to the field of marine water craft, particularly to high speed power boats utilizing a surface piercing propeller drive system mounted within a propeller tunnel formed integral to the hull of the boat, and most particularly to inclusion, within a wall of said tunnel, of a means for providing air thereto; said means being judiciously placed for linearization of the relationship between vessel velocity and engine speed.