OMC outdrive parts *Repairing lower unit or replacement

400-800 series installation / lower unit repair
steps 1 to 20

Last updated on 2/24/2023, 2:26:17 AM

  • 400-800 OMC boat repair photos
  • Co-manufacturer and distributor for GLM Products including aftermarket with 2 year limited warranty on parts

OMC outdrive parts *Repairing lower unit or replacement

Sandblast outdrive parts

Lower unit is disassembled, and placed into the sandblast area

inside gearcase and out

The outside and inside of the housing is sandblasted, removing all rust and corrosion

Sterndrive rebuild parts

For replacement rebuilt lower units, a new propeller shaft (GLM P/N 22414, 1-3/16″) is installed.

For customer units, a dial indicator is used to determine if the propeller shaft is out of round (bent). This would not be visible to the eye when turning so the tool is required. The threshold we use to determine if it needs to be replaced is .004″ out of round. Any more than that, and continued use of the bent unit would damage the oil seals and allow for water to enter the gear case and oil to leak out.

reverse gear

Reverse gear is installed

Pinion gear

Pinion gear is installed

Forward gear set

For rebuilt units, a new forward gear and pinion are installed.

For customer units, the forward and pinion are inspected for any chips or cracks on the teeth – or excessive pitting that would effect the integrity of the tooth on the gear. If found, a new forward/pinion set is installed.

forward bearing retainer

The forward bearing housing assembly is installed (GLM P/N 27700, replaces 389455). This has the bearing pre-installed into the housing.

Clutch dog

A new clutch dog is installed (GLM P/N 22625, replaces 337774).

For customer repair jobs, the teeth (corners) on the clutch are inspected – if there are signs of wear, in which the edges are beginning to or have rounded out, a new clutch is installed. Re-using a worn clutch would continue to cause problems with shifting, possibly loss of forward and reverse or shift cable damage.

Drive shaft

The vertical drive shaft is installed.

For customer lower units, the unit is inspected for excessive wear or damage to the threaded area. In many instances, the boat parts can be repaired using a lathe. Shaft must be replaced if it is not repairable.

Drive shaft
Swivel bearing retainer

The swivel housing is installed. It is sandblasted, primed and painted before installation and the face is machined to make sure it seats flush onto the lower unit / gasket.

bearing carrier
The bearing carrier is sandblasted and primed, and the bearing (P/N 11410, replaces 387247) and the reverse gear bearing are pressed in.
Upper bearing retainer

The upper bearing retainer is installed – cleaned and primed


All gears are shimmed to correct OEM specifications

Forward assembly
Forward gear and clutch are assembled
New intake screen installed

The intake screen is installed and painted to match outside case color

Zinc chromate paint

Zinc chromate primer is used on the inside of the housing

1-4 inch holes re-tapped

*800 series and Cobra lower unit repair photos.
Click here for steps 21-40 in the repair process