Mercruiser outdrive parts drawing *Videos *SEI sterndrive

T.C. Electronics/Marine Home Page

*New SEI outdrive upper gearcase

SEI replacement upper/lower unit - Mercruiser sterndrive models 120 - 140 - 165 - 470 - 888

  • Complete lower unit gear housing replaces the Mercruiser MC-1/R/MR/Alpha 1 (One) with 2 year warranty
  • For 120/140 4 cylinder serial numbers 2791957 - 6225576, 470/485 model serial numbers 4208730 - 6225575, 165 and all V8 models 1971 - 1990
  • Forward bearing size: outer diameter 3.500 inch (#21590)
  • Replaces Mercury outdrive OEM # 1623-8951A43
  • GLM aftermarket #18100 with gear ratio 13:21
  • Tech support Exploded view drawings
  • For upper unit outdrive parts, see our upper gearcase page for all parts with photos

SEI 106 Aftermarket Mercruiser Alpha 1 upper sterndrive

P/N SEI-106-1.50

  • Mercruiser 1 / R / MR / Alpha One complete upper unit.
  • Years 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.

SEI 106 Aftermarket Mercruiser Alpha 1 upper sterndrive

SEI 106 Aftermarket Mercruiser Alpha 1 upper sterndrive

P/N SEI-106-1.98
  • Mercruiser R/MR/Alpha One Gen 1 complete upper unit.
  • For 1970 - 1990 models, 4 cylinder
  • 1.94 / 1.98 gear ratios with
    20-24 tooth count
  • Compatible with 120 to 140 horsepower models with a 2.5 or 3.0 liter motor
  • Years 1971 to 1990, 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 inch. If your shaft is the 'short style' which measures 8-1/8 inches, please contact us for availability.

SEI 106 Aftermarket Mercruiser Alpha 1 upper sterndrive

SEI 106 Aftermarket Mercruiser Alpha 1 upper sterndrive

P/N SEI-106-1.81

  • Mercruiser R/MR/Alpha One Gen 1 complete upper unit
  • Years 1976 - 1982 models with 4 cylinder
  • 470 / 485 models and 1986 - 1990
  • 4.3 liter V6. 1.81 / 1.84 gear ratio with a 17-19 tooth count
  • Compatible with inline 4 cylinder 3.7 liter motors serial numbers 4208730 to 6225576
  • and 4.3 liter 185 / 190 horsepower V6 motors serial numbers 6225577 to 0D469858

*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 inch. If your shaft is the 'short style' which measures8-1/8 inches, please contact us for availability.

SEI 106 Aftermarket Mercruiser Alpha 1 upper sterndrive

SEI 106 Aftermarket Mercruiser Alpha 1 upper sterndrive

P/N SEI-106-1.65

  • Mercruiser R/MR/Alpha One Gen 1 complete upper unit.
  • Years 1970 - 1977 models with 165 horsepower inline 6 cylinder
  • 1.65 / 1.62 gear ratio with a 24-24 tooth count
  • Compatible with 165 models serial numbers 2763442 and up.

*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 inch. If your shaft is the 'short style' which measures 8-1/8 inches,please contact us for availability.

SEI aftermarket Mercruiser Alpha One lower unit

SEI aftermarket Mercruiser Alpha One lower unit

P/N SEI-106

  • Mercruiser 1 / R / MR / Alpha One
  • Complete lower unit
  • Years 1970 - 1990 models
  • Serial numbers 2791957-OD469858
  • 13 spline vertical driveshaft
  • 120/140 4 cylinder models 470 / 485
  • 160/165 6 cylinder
  • Up to 300 horsepower

SEI aftermarket Mercruiser Alpha One sterndrive

SEI item number 18100 lower unit OEM number 1623-8951A43

SEI aftermarket Mercruiser Alpha One Gen 2 outdrive

SEI 116 Mercruiser Alpha 1 gen 2 upper sterndrive
SEI 116 Mercruiser Alpha 1 gen 2 upper sterndrive

P/N SEI-116-1.47
  • Mercruiser Alpha One gen 2 complete upper unit
  • Years 1991 - up models with 230 / 260 horsepower V8 motors
  • 1.47 gear ratio with a 20-22 tooth count
  • Compatible with 5.0 liter 305 and 5.7 liter 350 models Mercruiser serial numbers 0D470000 and up

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

SEI Mercruiser Alpha One gen 2 sterndrive
SEI Mercruiser Alpha One gen 2 sterndrive

Lower unit replacement for Mercruiser Alpha 1 gen 2