SEI Marine Products

The SE421(90-421-A20) comes with the 1.81:1 Gear Ratio, and a 20" Drive Shaft. This is a standard right hand rotation gear case. It replaces gear cases on Yamaha 2 Stroke V6 3.1 and 3.2 Engines with Right Hand Rotation. The paint color for all lower units is transitioning to black as inventory becomes depleted. Therefore, color may vary depending on product availability at time of order.
SE-421-1-81-20 Driveshaft-66K-45300-12-NA

This SE421 (90-421-A25) Replaces the Gear Case on Yamaha V6 2 Stroke 3.1 and 3.2 Liter Engines with Standard Right Hand Rotation. 1.81:1 Gear Ratio 25 Inch Drive Shaft. The paint color for all lower units is transitioning to black as inventory becomes depleted. Therefore, color may vary depending on product availability at time of order.
SE-421-1-81-25 Driveshaft 60V-45300-20-8D

SE421 1.81:1 Ratio / 30"" Shaft / 2 Stroke V6 / RH Rotation The paint color for all lower units is transitioning to black as inventory becomes depleted. Therefore, color may vary depending on product availability at time of order.
SE-421-1-81-30 Driveshaft 60V-45300-30-8D

The SE421 (90-421-B25F) Replaces Gear Case on
Yamaha Four Stroke V6 200HP - 225HP Engines
with 2:1 Gear Ratio, 25 Inch Drive Shaft and
Standard Right Hand Rotation The paint color for all lower units is transitioning to black as inventory becomes depleted. Therefore, color may vary depending on product availability at time of order
SE-421-2-0-69J-45300-21-8D

The SE421 (90-421-B30F) Replaces the Gear Case on Yamaha
Four Stroke V6 200HP - 225HP Engines with
30 Inch Drive Shaft and Standard Right Hand Rotation The paint color for all lower units is transitioning to black as inventory becomes depleted. Therefore, color may vary depending on product availability at time of order
SE-421-2-0-69J-45300-31-8D

Anode kit for SE421

SE421 Installation Kit

SE421 Installation Kit Fits OMC Needle Bearing

SE421 Installation Kit

Counter Rotation only. Replaces LF250 lower units with dual water intakes. Also replaces early LF250 lower units with side water intakes. This unit has the watercooled bearing carrier. It is painted black but you can paint it to match your engine.

The 90-428-A25 is a Counter Rotation (Left Hand Rotation) Gear Case. This gear case replaces most Yamaha 2 Stroke V6 3.1 and 3.2 Liter (225HP / 250HP) Engines with 1.81:1 Gear Ratio and 25 Inch Drive Shaft. For Counter Rotation only, do not use for Standard Rotation. The paint color for all lower units is transitioning to black as inventory becomes depleted. Therefore, color may vary depending on product availability at time of order
SE-428-1-81-25 Counter Rotation 60W-45300-20-8D

The 90-428-A30 is a Counter Rotation (Left Hand Rotation) Gear Case This gear case replaces most Yamaha 2 Stroke V6 3.1 and 3.2 Liter (200HP/225HP/ and some 250HP) Engines with 1.81:1 Gear Ratio and 30 Inch Drive Shaft. For Counter Rotation only, do not use for Standard Rotation. The paint color for all lower units is transitioning to black as inventory becomes depleted. Therefore, color may vary depending on product availability at time of order
SE-428-1-81-30 Counter Rotation 60W-45300-30-8D

The 90-428-B25F is a Counter Rotation (Left Hand Rotation) Gear Case. This gear case replaces most Yamaha Four Stroke V6 200HP - 225HP Engines with 2.0: 1 Gear Ratio and 25 Inch Drive Shaft. For Counter Rotation only, do not use for Standard Rotation. The paint color for all lower units is transitioning to black as inventory becomes depleted. Therefore, color may vary depending on product availability at time of order.
SE-428-2-0-25 Counter 4 Stroke 69K-45300-21-8D

The 90-428-B30F is a Counter Rotation (Left Hand Rotation) Gear Case. This gear case replaces the gear case on most Yamaha Four Stroke V6 225 HP Engines with 2.0: 1 Gear Ratio and 30 Inch Drive Shaft. For Counter Rotation only, do not use for Standard Rotation. The paint color for all lower units is transitioning to black as inventory becomes depleted. Therefore, color may vary depending on product availability at time of order.
SE4-28-2-0-30 Counter 69K-45300-31-8D 4 Stroke

Counter Rotation only. Replaces LF250 lower units with dual water intakes. Also replaces early LF250 lower units with side water intakes. This unit has the watercooled bearing carrier. It is painted black but you can paint it to match your engine.

Includes all seals, o'rings and bearings for the gearcase.


Johnson / Evinrude outboard
1978 - 1998
4.250" Diameter gearcase with four bolt bearing carrier
88-140 HP


OMC Sterndrive
1982-1985
Most four cylinder (4.250" diameter gearcase)
Mechanical shift only (not hydro-shift)


OMC Cobra
1986 - 1990

Fits 1972-1982 Mercruiser "R" style lower.
This lower is the style that has the preload pin on the driveshaft.
Includes all seals and bearings for the lower unit.

SEAL & BEARING KIT Fits Mercruiser Repair Kit 93-104-700K

Fits OMC Stringer lower.
Most 4 cylinder engines.
4-1/4" diameter gearcases only.
Mechanical shift only.
1978-1985.
Includes all seals and bearings for the lower unit.

Includes all seals, o'rings and bearings for the upper unit.

Fits most Mercruiser I, R, MR and Alpha I upper units. 1973-1990.
For 1.50 gear ratios only.
For use with 1-25/32" OD top cap bearing.
Not for 1.62 / 1.81 / 1.94 ratio units.

SEAL & BEARING KIT Fits Mercruiser Repair Kit 93-106-400K

Includes all seals, o'rings and bearings for the upper unit.

Fits most Mercruiser I, R, MR and Alpha I upper units. 1973-1990.
For 1.50 gear ratios only.
For use with 1-15/16" OD top cap bearing.
Not for 1.62 / 1.81 / 1.94 ratio units.

SEAL & BEARING KIT Fits Mercruiser Repair Kit 93-106-401K

Includes all seals, o'rings and bearings for the upper unit.

Fits most Mercruiser I, R, MR and Alpha I upper units. 1973-1990.
For 1.81 / 1.94 / 1.62 gear ratios only.
For use with 1-25/32" OD top cap bearing.
Not for 1.32 / 1.50 ratio units.

SEAL & BEARING KIT Fits Mercruiser Repair Kit 93-106-402K