Mercruiser Alpha One gearcase (new lower unit)

Mercruiser outdrives Alpha 1 lower unit gearcase housing assembly from SEI Marine aftermarket replaces the original Alpha 1 and Mercruiser lower gear housings.

The Last updates were on 12/5/2019, 3:02:15 AM.

  • Replacement of New complete lower unit gear housing assembly
  • Forward bearing size: O.D 3.500
  • The original Mercruiser and Alpha 1 (One) and Gen 2 lower units are replaced by Heavy-duty construction
  • SEI P/N SE106 for 1970-1990 models, and P/N SE116 for 1991 and up (Alpha Gen 2 models)
  • Gear Ratio:13:21
  • OEM 1623-8951A43

Available products are listed below:

P/N SE106 Mercruiser R/MR/Alpha One Gen 1 complete lower units. For 1970 – 1990 models, serial numbers 2791957-OD469858.

P/N SE116 Alpha One Gen 1 Generation 2 complete lower units. For 1991 and up models with metal water pump and impeller housing, serial numbers OD470000-Up.

Products of Mercruiser aftermarket Alpha one and generation 2 upper gear cases are listed below:

P/N SE106-198 Mercruiser R/MR/Alpha One Gen 1 complete upper unit. For 1970 – 1990 models, serial numbers 2791957 to 6225576.

*Note – before ordering, please measure your output shaft that goes into the engine. Replacement upper units come with an output shaft that measures 9-9/16 inches. If your shaft is the ‘short style,’ which measures 8-1/8 inches, please contact us for availability.

P/N SE106-181 Mercruiser R/MR/Alpha One Gen 1 complete upper unit. For 1976 – 1982 models with four cylinders 470 / 485 models, serial numbers 6225577 to 0D469858.

P/N SE106-165 Mercruiser R/MR/Alpha One Gen 1 complete upper unit. For 1970 – 1977, models with 165 horsepower inline six cylinders, 1.65 / 1.62 gear ratio with a 24-24 tooth count.

Compatible with 165 models serial numbers 2763442 and up.

P/N SE106-150 Mercruiser R/MR/Alpha One Gen 1 complete upper unit. For 1974 – 1990 models with 205 / 230 / 260 horsepower V8 motors, 1.47, and 1.50 gear ratio with a 20-22 tooth count.

Compatible with 888, 898, 228, 225-S, 233, 250, 260, 5.0 liter 305 and 5.7 liter 350 models serial numbers 2763442 and up.

P/N SE116-147 Mercruiser Alpha One Gen 2 complete upper unit. For 1991 and up models with 230 / 260 horsepower V8 motors, 1.47 gear ratio with a 20-22 tooth count.

Compatible with 5.0 litre 305 and 5.7 litres 350 models serial numbers 0D470000 and up.

*Note – does not work with the 305 V8 200 horsepower model.

P/N SE116-194 Mercruiser Alpha One Gen 2 complete upper unit. For 1991 – up models with four-cylinder motors, 1.94 gear ratio with a 20-24 tooth count.

Compatible with 3.0L and 3.0LX models serial numbers 0D470000 and up.

P/N SE116-181 Mercruiser Alpha One Gen 2 complete upper unit. For 1991 – up models with 4.3-litre V6 motors, 1.81 gear ratio with a 17-19 tooth count.

Compatible with 4.3L and 4.3LX models serial numbers 0D470000 and up.

WARRANTY that is available on these products:

All products manufactured by (“SEI”) are covered by warranty for either one (1) year for upper gear cases purchased without u-joints and output shafts, or two (2) years for lower units and top gear cases purchased with u-joints and output shafts from the date of actual purchase. A condition of qualification of these warranties is proof of purchase of the SEI product. Proof of purchase must be supplied by the customer before the warranty application and/or receiving warranty benefits. This one (1) year and two (2) year warranties against manufacturing defects in quality/craft and components are the sole and exclusive warranty provided by SEI, and all other warranties and potential damages are limited and excluded. These warranties commence on the shipment date of products to the customer sold by TC Electronics to the purchaser.

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