This SEI Marine Counter-Rotation Lower Gear Set is a precision-engineered replacement for MerCruiser Alpha One sterndrives manufactured from 1972 to 1990.
Featuring a 1.62:1 gear ratio, this set provides smooth reverse-rotation operation and consistent power transfer for counter-rotating lower units.
It replaces OEM 812975A5 and 824700A1, offering a direct-fit solution for Alpha I sterndrive applications.
Constructed from high-strength marine-grade steel and designed to meet or exceed OEM standards, this SEI gear set ensures long-term reliability and quiet performance.
Backed by SEI’s 3-Year Fault-Free Warranty, it’s built for lasting durability and precision alignment.
Product Features
- Direct OEM Replacement: Replaces MerCruiser OE# 812975A5 and 824700A1
- Fitment: MerCruiser Alpha One sterndrives (1972–1990)
- Rotation: Counter Rotation (Left-Hand)
- Gear Ratio: 1.62:1
- Construction: Marine-grade precision-machined gears for strength and corrosion resistance
- Condition: 100% brand-new SEI Marine replacement gear set
- Warranty: 3-Year Fault-Free Warranty provided by SEI Marine
Additional Information
Note: Designed specifically for counter-rotating Alpha One lower units from 1972–1990.
If you require the standard-rotation (right-hand) gear set or components for newer Gen II drives, please email or fill out the contact form and we will help you locate the correct parts.
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.
