Mercury Mercruiser Alpha One Gen I Upper Driveshaft Assembly (1969-1990)

This is a brand new genuine Mercury upper driveshaft assembly (also known as the upper gearcase or upper unit) for MerCruiser Alpha One Generation I sterndrives, compatible with models from 1969 to 1990 (serial numbers up to approximately 0D469858). It includes a 2-year manufacturer warranty.

Available Gear Ratios: Please select your required gear ratio below:

• 1.50:1 – Commonly used with V8 engines (e.g., 5.7L/350, higher HP models)
• 1.65:1 – Commonly used with inline 6-cylinder engines (e.g., 165 HP 3.7L/224) or some 4.3L V6 in heavier boats
• 1.84:1 – Commonly used with 4-cylinder (e.g., 470/485 series) or some 4.3L V6 applications
• 1.98:1 – Commonly used with 4-cylinder engines (e.g., 2.5L/120-140 HP, 3.0L/130-135 HP)

Please note: This item is typically not stocked in store and ships directly from the manufacturer.

Important Fitment Information: To make sure you receive the correct upper unit with the proper gear ratio, please provide your engine's serial number and model number from the transom bracket (or engine details like HP and cylinders). We're here to help verify the exact match!

Special Note for Older Units: For Alpha One serial numbers 0D494569 and below (typically pre-1991), as well as older "R" style units with 4-cylinder or 6-cylinder engines, the upper driveshaft yoke (input shaft) length may differ. These often require reuse of your existing input shaft/yoke for proper fitment. Please confirm your yoke measurement or provide details so we can advise.

This upper driveshaft assembly comes complete and ready for installation, with no core charge required.

Extended warranty: An optional 12-month extended warranty is available: $438 for 4-cylinder, $540 for 6-cylinder, or $607 for V8 engines (must be added within 30 days of purchase).

If you have any questions, email us at orders@hawkeyemarine.net or call 615-691-1433. We're ready to help with your purchase.

About Hawkeye Marine: As a dealer for OBR Parts and Marine (established 1982), we sell new and remanufactured powerheads, lower units, and sterndrives, backed by fitment help from outboard specialists.