Sierra 18-4220 Marine Thrust Washer for Mercury/Mariner Outboard Motors, Replaces 13171, 77987, White

The Sierra 18-4220 is a marine thrust washer engineered for Mercury/Mariner outboard motors, with application in V-6 outboards and Mercruiser sterndrives. Machined from alloy steel with a glossy white finish, this washer is built to meet or exceed original equipment quality standards, providing the precise thrust bearing surface needed to support proper propeller shaft alignment and load distribution in the lower unit. Thrust washers like the 18-4220 sit against the propeller shaft to absorb axial thrust loads generated during operation, protecting the gearcase from wear and helping maintain correct shaft positioning. Using a properly sized, quality thrust washer during a lower unit rebuild or propeller shaft service helps prevent premature wear to surrounding gearcase components. The Sierra 18-4220 is sold as a single piece and is dimensioned at 0.39 x 0.39 x 0.39 inches, making it a compact but critical component in the lower unit assembly. It is compatible with Mercury/Mariner outboard motors and Mercruiser sterndrives using the OEM numbers listed below, giving buyers a reliable aftermarket equivalent for repair or rebuild work.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-4220
• Product Type: Thrust Washer
• Material: Alloy Steel
• Finish: Machined, Glossy
• Color: White
• Weight: 0.53 pounds
• Dimensions: 0.39 x 0.39 x 0.39 inches
• Application: Marine
• Package Quantity: 1
• UPC: 030999317674

Fitment

• Mercury/Mariner Outboard Motors
• V-6 Outboards and Mercruiser Sterndrives

Replaces (OEM)

• 13171
• 77987
• 12-835467-1
• RO96116

Frequently Asked Questions

What is the Sierra 18-4220 used for? The Sierra 18-4220 is a marine thrust washer that sits against the propeller shaft in the lower unit to absorb axial thrust loads and support correct shaft alignment.

Does the 18-4220 fit Mercury outboards? Yes, the Sierra 18-4220 thrust washer is designed for Mercury/Mariner outboard motors as well as V-6 outboards and Mercruiser sterndrives.

What OEM part numbers does the 18-4220 replace? The Sierra 18-4220 replaces Mercury/Mercruiser OEM numbers 13171, 77987, 12-835467-1, and Pleasurecraft RO96116.

Is this an OEM or aftermarket part? The Sierra 18-4220 is an aftermarket thrust washer manufactured to meet or exceed original equipment quality standards for the Mercury/Mercruiser OEM numbers it replaces.

What material is the 18-4220 thrust washer made from? It is made from alloy steel with a machined, glossy finish in white.

What size is the Sierra 18-4220 thrust washer? The 18-4220 measures 0.39 x 0.39 x 0.39 inches and weighs 0.53 pounds.

How many washers come in one order of the 18-4220? Each order of the Sierra 18-4220 includes one thrust washer.

Is the 18-4220 compatible with Mercruiser sterndrives? Yes, the Sierra 18-4220 is compatible with V-6 outboards and Mercruiser sterndrives in addition to Mercury/Mariner outboard motors.

When would I need to replace a thrust washer like the 18-4220? A thrust washer is typically replaced during a lower unit rebuild or propeller shaft service, especially if the existing washer shows wear from absorbing axial thrust loads.

Does the 18-4220 have a specific color or finish? The Sierra 18-4220 has a white, glossy machined finish on its alloy steel construction.

What is the Pleasurecraft equivalent of the Sierra 18-4220? The Sierra 18-4220 is equivalent to Pleasurecraft OEM number RO96116.