11-81772M – NUT – Mercury-Mercruiser

The 11-81772M Mercury nut secures pinion gears and driveshaft components in Mercury, Mariner, and Mercruiser outboards. It keeps rotating parts tight and aligned in the gearcase assembly. You find this nut on drive and gearcase diagrams for many older engines. Many enthusiasts seek this OEM part when restoring classic gear housings.

This 11-81772M Mercury nut fits the original threads and torque specs. You install it on the pinion side or driveshaft bearing retainer to prevent axial movement under load. Additionally, it works with lock washers or locking plates to hold tight in vibration environments. Always confirm fit on your engine model before purchase because older outboards have varied hardware.

Over time, nuts in gearcase areas can corrode or loosen. That can cause gear chatter or unusual noise. You may also feel slack in the drive or detect loss of smooth gear engagement. In some cases, wear lets the pinion move under load. This increases risk of misalignment, chatter, or expensive gear damage. Replacing worn hardware with the correct fastener restores secure mounting and reduces wear.

Shop at Arizona Outboard Dismantlers to keep your outboard running strong and ready for the water.