Keyway 331901

Function and Technical Context

The shear pin 331901 is the torque transmission element responsible for coupling the shaft with the pinion, flywheel, or propeller hub in OMC, Johnson, and Evinrude outboard motors. Housed in the keyway machined into the crankshaft or propeller shaft, it acts as a mechanical coupling that prevents any relative rotation between the shaft and the connected component, thereby ensuring perfect synchronization of the rotating assembly. When this component operates at the end of the propeller shaft, it also fulfills a calculated sacrificial function: in the event of a sudden impact of the propeller against a solid object, the shear pin absorbs the shearing stress and fails before damage transfers to the shaft or hub, protecting components of much higher value. Silent deterioration of the shear pin—due to fatigue, crushing, or micro-cracking—causes progressive misalignment of the rotating components, loss of transmission efficiency, and ultimately costly secondary failures in the shaft itself or in the hub of the connected component.

When to Replace This Component?

The clearest signs that the shear pin is worn or sheared are: noticeable play or rattling in the shaft coupling, a loss of throttle response due to slippage between the shaft and the connected element, or sudden breakage immediately after a propeller strike against a subsurface obstacle, a situation especially common in OMC outboard motors. It is recommended to visually inspect the shear pin at each seasonal maintenance interval, discarding it if any crushing marks, deformation, or cracks are present, however small they may appear. Replacing it preventatively represents a minimal investment that eliminates the risk of losing propulsion while underway and avoids costly propeller shaft or hub repairs.

Compatible Johnson/Evinrude Engines

Equivalent Manufacturer References