This SEI Marine Lower Gear Set is designed for MerCruiser Alpha One and Alpha One Gen II sterndrives with serial numbers 0F679999 and below.
Featuring a 1.62:1 gear ratio and a 3.500" O.D. forward gear bearing, this set provides smooth power transfer, precise engagement, and dependable torque handling.
It replaces OEM 43-878087A4 and 43-828073A1, and is also compatible with SE106 and SE116 units.
Additionally, it fits 3.0L Mercury Outboard units with 1.62 / 1.64:1 ratios (3.500" forward bearings only).
Built to OEM standards and backed by SEI’s 3-Year Fault-Free Warranty, this gear set ensures reliable operation and long service life in demanding marine conditions.
Product Features
- Direct OEM Replacement: Replaces MerCruiser OE# 43-878087A4 and 43-828073A1
- Fitment: MerCruiser Alpha I and Alpha I Gen II (1972–1997)
- Serial Range: Fits Alpha I units with serial numbers 0F679999 and below
- Additional Fitment: SE106 and SE116 drives
- Engine Compatibility: Also fits 3.0L Mercury Outboards with 1.62 / 1.64:1 ratios (3.500" forward bearings only)
- Gear Ratio: 1.62:1
- Bearing Size: Includes 3.500" O.D. forward gear bearing
- Condition: 100% brand-new SEI Marine replacement gear set
- Warranty: 3-Year Fault-Free Warranty provided by SEI Marine
Additional Information
Note: This gear set includes the 3.500" O.D. forward gear bearing and is compatible with both Alpha I and Alpha I Gen II drives within the specified serial range.
If you require a gear set for a different ratio or bearing size, please email or fill out the contact form and we’ll assist in locating the correct part.
Shipping Information
SHIPPING: Additional shipping fees to Alaska, Hawaii, U.S. Territories, or international destinations will be calculated after checkout.
You will receive an email and a PayPal money request for the additional shipping charges at the email address provided.
(Some items are excluded from international shipping.)
Customer Support
For questions or to confirm compatibility, please email customerservice@marinepartswarehouse.com .
Please include your engine model number to help confirm proper fitment before ordering.
