Abstract: An auxiliary engine propeller shaft locking device for sail boats and the like comprising, a base having an upper lock housing and a lower shaft housing; the housings being integral and in substantially abutting relation with each other. The shaft housing includes a rotatable propeller shaft disc mounted thereon having an inner and outer surface. The housings have front and back surfaces, with the shaft disc mounted on the shaft housing front surface, and the lock housing front surface being above the shaft housing front surface. The disc outer surface is below the plane of the front lock housing surface and the disc inner surface is above the plane of the shaft housing front surface to provide rotating clearance for the disc. The shaft disc has a width less than the width of the shaft housing to provide rotating clearance for the disc. The lock housing includes a locking pin and a shot pin for the locking pin, and the disc includes locking pin engaging means.