Pin-drive

Pin-drive

Pin-drive systems are not as commonly used as splined shaft drives of more than 9.9 HP. This type of propeller drive was more commonly used 20+ years ago, but even then, they were commonly used on engines less than 75 Hp. One exception to this were OMC sterndrives built before 1977. The pin-drive uses a smooth surface propshaft with a hole drilled through it, perpendicular to the axis of rotation. A short pin is then inserted into the hole so that it protrudes equally out the sides of the propshaft. This protrusion then engages cutouts in the prop so that the pin drives the propeller around as the shaft rotates. Pin-drives tend to be non-thru-hub exhaust units as well. This is seen when the propeller is removed from the gearcase and no exhaust ports are observed between the propeller and the gearcase. Propellers for pin-drives have slots cut into the propeller perpendicular to the prop shaft hole. These slots engage the shear-pin which drives the propeller around. These slots are highlighted in yellow in the picture above.