Description
New MerCruiser Alpha I Lower Unit – Fits Gen 1 Outdrives (1972–1990) – Aftermarket Replacement
This brand-new aftermarket lower unit is built to directly replace damaged or worn MerCruiser Alpha One Gen 1 gearcases manufactured between 1972 and 1990. Designed with precision and compatibility in mind, this unit is ideal for restoring performance to 3.0L, 4.3L, and other small block MerCruiser sterndrive systems.
Whether you’re working on a MerCruiser 3.0, Alpha One 4.3, or need a reliable lower gear housing solution for your older inboard/outboard setup, this part delivers dependable quality without the cost of OEM parts. The unit is finished in durable black and comes ready for final assembly using your original internal components.
This lower unit is non-OEM, not remanufactured, and does not include the upper driveshaft, water pump, or shift shaft — these will need to be transferred from your original assembly.
Pricing
Total Price: $1,295
Less $200 Core Rebate Final Price: $1,095
Product Finish:
- Brand-new construction, not remanufactured
- Durable black coating
- Built to match Alpha One Gen 1 specifications
Core Rebate Information
- Return your old core, get up to $200 back
- Rebate amount will vary based on the condition of your core
- ♻️ Recycle your core- keep boat parts out of the landfill
Useful Resources
- 🔍 How to find your Boat Engine serial number?
- Still deciding? Watch our YouTube video How to avoid common lower unit replacement mistakes
- To help extend the life of your gearcase, check out our Boat Maintenance Checklist






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