Upper Unit Boat Outdrives 1973 - 1990
1973-1990 Model Years, replaces Alpha One Gen 1New, Not Rebuilt! Sterndrive Engineering manufactures and markets new replacement drives with a 3-year Fault Free Manufacturer's Warranty. The SE-106 Upper Unit replaces most Mercruiser models made from 1973-1990, including all Mercruiser Alpha One Gen 1, R and MR outdrives. Comes with a 9-9/16 inch new style input yoke. If the "Short Input Shaft" version is selected, the input shaft length is 8-1/8 inches long. Does not include Complete Install Kit or Anode Kit, which can be ordered separately. 1.47 or 1.50 Ratio, Replaces Alpha One Gen 1 (1973-1990 model years) 90-106-01D 1.62 or 1.65 Ratio, Replaces Alpha One Gen 1 (1973-1990 model years) 90-106-01C - $695.00 1.62 or 1.65 Ratio Short Shaft, Replaces Alpha One Gen 1 (1973-1990 model years) 90-104-01C - $695.00 1.81 or 1.84 Ratio Short Shaft, Replaces Alpha One Gen 1 (1973-1990 model years) 4.3 liter V-6 engines with carb, 3.7 liter engines, and 470, 485, & 488 4-cylinder engines. Comes with a 8-1/8 input yoke. This drive is generally used on older inline 6 and 4 cylinder engines. 90-104-01B - $695.00 1.81 or 1.84 Ratio, Replaces Alpha One Gen 1 (1973-1990 model years) 90-106-01B 1.94 or 1.98 Ratio, Replaces Alpha One Gen 1 (1973-1990 model years) 90-106-01A - $695.00 1.94 or 1.98 Ratio Short Shaft, Replaces Alpha One Gen 1 (1973-1990 model years) 90-104-01A - $695.00
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To check for the proper gear ratio for your sterndrive, please reference table below:
| Boat Engine Size | Sterndrive Gear Ratio |
|---|---|
| 350 cubic inch, 5.7 liter, 350 MAG, 5.0 EFI engines | 1.47 ratio, 1.50 ratio |
| Carbureted 305 cubic inch, 5.0 liter carb, 4.3 liter EFI and Inline 6 engines |
1.62 ratio, 1.65 ratio |
| 4.3 liter V-6 engines with carb | 1.81 ratio, 1.84 ratio |
| 3.7 liter and 470, 485 and 488 4-cylinder engines | 1.81 ratio, 1.84 ratio |
| 120, 140, 3.0 liter engines | 1.94 ratio, 1.98 ratio |
Please note that Mercruiser changed their gear ratios somewhat in the mid-1980s (for example a V-8 gear ratio used to be 1.50, but Mercruiser now uses 1.47 ratio.) Select the outdrive gear ratio based on your engine size.
Call us toll-free at (866) 969-0441 anytime to place an order or if you have questions or need further information. We welcome the opportunity to help find the correct upper unit outdrive or any Sterndrive Engineering Marine boating part you may need.
Call us toll-free at 866-969-0441 to place an order or for assistance at any time. 
GetBoatGear.com is an authorized dealer for Sterndrive Engineering Marine products. Boating items we currently offer include complete, lower, and upper unit outdrives, outdrive install kits, transom repair parts, shift cables, anode kits, trim cylinders, trim cylinder hoses, and boat propellers. We welcome the opportunity to help find the parts and items you need for your boat.