Yamaha - Dog Clutch 6FM-45631-00-00. Overview. The Yamaha Dog Clutch 6FM-45631-00-00 is one of those parts that makes or breaks how clean your engine shifts. When it starts to wear down, you'll usually hear it first-grinding, slipping, or hard engagement going into gear. It's what locks the gears together inside the lower unit, so it has to stay sharp and properly aligned. If your shifting doesn't feel solid anymore, this is often a key piece to look at.. Key Features. • Positive Gear Engagement - Locks gears together securely for reliable forward and reverse operation.. • OEM Fit Precision - Built to Yamaha specifications for proper alignment and smooth gear interaction.. • Smooth Shifting Support - Helps reduce grinding and improves gear transition feel.. • Heavy-Duty Construction - Designed to handle torque, load, and repeated marine use.. Compatibility. Compatible with select Yamaha outboard engines using this dog clutch configuration.Commonly found in Yamaha lower units requiring