Yamaha - Gear 2 (26T) Lower Unit Gear 6DA-45571-00-00. Overview. When you're inside a Yamaha lower unit, you quickly learn that every gear has to do its job without hesitation. This 26-tooth gear is built for that exact purpose-keeping things turning smoothly when you shift and put power down. It's the kind of part you don't think about until something feels off, and then you realize how important clean, reliable gear engagement really is. Swap in a solid gear like this, and the whole drivetrain