Abstract: A drive mechanism for a watercraft having a surface propeller rotatingly driven by a motor arranged inboard of the watercraft through shafting which extends through an opening in a transom plate on the watercraft. The shafting includes a propeller shaft which is rotatably supported in a support arm which is mounted externally of the watercraft and on the aforesaid transom plate. The support arm is of a unitary construction and has appropriate openings therein to rotatably support the propeller shaft. Thrust bearings are provided on the support arm to absorb the thrust forces generated by the propeller. Due to the unitary construction of the support arm, the thrust forces generated by the propeller are transmitted only through rigid parts onto a flange plate on the support arm which in turn is fixedly secured to the transom plate.