Yamaha - Woodruff Key Flywheel & Shaft Alignment 90280-04M00-00. Overview. This woodruff key is one of those parts you don't notice until something's off with the way your engine runs. It's what keeps everything lined up on the shaft so timing stays where it should be. I've pulled apart setups where a worn key caused all kinds of headaches that could've been avoided with a simple replacement. It's small, but it's doing critical work every time that motor turns over.. Key Features. Precision Alignment Support - Keeps rotating components properly indexed for correct engine timing.. Anti-Slip Engagement - Locks parts in place to prevent movement under load.. Durable Metal Construction - Built to handle torque and repeated engine cycles.. Exact Fit Design - Matches Yamaha specifications for secure seating in the shaft.. Engine & Boat Compatibility. Used in a variety of Yamaha outboard applications involving flywheels, crankshafts, and other keyed shaft components. Essential anywhere precis