Yamaha Replacement Lower Unit | 1.81 | 25" | 2 Stroke | 90-428-A25

Replacement Yamaha® Outboard Lower Unit — 25″ 2-Stroke | 1.81 Ratio

Part # 90-428-A25

Aftermarket replacement, built to fit. This complete lower unit is an aftermarket replacement for Yamaha 2-Stroke outboards that require a 25″ shaft and 1.81 gear ratio. It ships fully assembled—with the water pump and internal components installed—for smooth shifting, dependable operation, and long service life.

Product Summary

• Replacement Yamaha fitment — for 2-Stroke outboards with a 25″ shaft
• 1.81 gear ratio — matches original performance specification
• Fully assembled — install and go (water pump & internals pre-installed)
• Precision-machined internals — gears, shafts, and bearings for reliable performance
• Durable black finish — can be refinished to match your engine

Fitment: Please verify your engine’s model and year, shaft length (25″), gear ratio (1.81), and rotation (standard or counter) before ordering.

Need help confirming fitment? Contact us.

Yamaha® is a registered trademark of Yamaha Motor Co., Ltd. This is an aftermarket replacement part and is not manufactured by or affiliated with Yamaha. Names are used for fitment reference only.