Mercruiser Part *Cover Nut

Mercruiser outdrive parts drawing *Videos *SEI sterndrive

Mercruiser Part *Cover Nut

GLM Aftermarket cover nut for stern drive lower gearcase

GLM P/N 21120 replaces Mercury 79448 or Sierra 18-9858
Removal and installation instructions shown below
Tech support Exploded view drawings
Compatible with all Mercruiser models from 1964 and up (except Bravo 3)

21120 Cover nut lower unit

21120 Cover Nut

P/N 21120 OEM 79448 $21.99

Help with Removing This Part
Begin by prying straight the tabs on the locking washer around the nut. If you damage the tabs you'll need to replace it. Use tool #90190 (or Mercury #91-61069T), which can be purchase below, to remove the nut. Using the tool, turn it counter-clockwise. In the event that the part is completely seized into the housing due to corrosion, you can use a drill to drill out the frozen piece. Remove it along with the key washer and the aligning key. When re-installing this item, make sure to clean around the internal threads in the lower unit before using the tool to install (turning clockwise) the new item.

Customers who ordered P/N 21120 also purchased:

90190 Mercruiser tool bearing carrier retainer wrench

P/N 90190 Retainer wrench tool removes and installs the cover nut in front of the bearing carrier. Replaces OEM 91-61069T, Sierra P.N 18-9858. $112.99

11380 Tab Washer

Tab washer P/N 11380. This part will need to be replaced if you damaged the tabs on the old one when removing the nut. Replaces OEM 14-79447, Sierra P/N 18-2299.

87510 Seal Kit 26-33144A2

P/N 87510 Lower gear case seal kit is required when re-assembling the parts in lower unit. Replaces OEM 26-33144A2, Sierra P/N 18-2652.