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 precise alignment is required to maintain proper engine timing and performance. Always confirm sizing and fitment before installation.

FAQ

Q: What usually causes a woodruff key to fail?
A: Most of the time it’s from improper installation, over-torque, or wear from components slipping.

Q: Can I install this without removing major engine parts?
A: It depends on location, but many times you’ll need to remove the flywheel or related components.

Q: Should the key sit flush in the shaft?
A: Yes, it should sit snug and even—if it’s sticking up or loose, something’s not right.

Q: Is corrosion a concern with this part?
A: It can be over time, especially in saltwater, so clean installs and proper maintenance help.

Q: What’s a common mistake when installing a woodruff key?
A: Forcing it in at an angle or not seating it fully, which can lead to immediate issues once the engine runs.