Abstract: This disclosure pertains to an air propulsion device for surface craft having a lateral platform designed to clampingly engage the gunwales of a craft and a clamp to removably attach the platform to the sternmost outboard motor mounting board. A propulsion motor mounting plate is pivotably secured to the lateral platform and is adapted with a pivot handle. The air propulsion motor is mounted atop the motor mounting plate within a triangular shaped supporting structure having, at its apex, a bearing assembly which supports the blade shaft. The entire unit can be assembled onto most small boat shapes when in the water or on land, and can be removed therefrom for repairs or to convert the boat to a conventional outboard driven craft when desired. The entire unit is self contained and the mounting devices employed thereon do not require any permanent modifications to the boat upon which it is to be mounted and operated.