Sierra Thrust Washer 18-4221 - Replaces Mercury 13191A1, 75282A1 - Fits 4 & 6 Inline 75-150 HP Outboards

The Sierra 18-4221 is a flat thrust washer engineered as a direct replacement for Mercury Marine outboard applications. Thrust washers sit against the propeller hub to take up axial load from the prop shaft, protecting the gearcase and propeller from wear during operation. This washer is built to Mercury 4 & 6 Inline 75-150 HP specifications and carries a machined finish for a precise, consistent fit against the hub and shaft.

Constructed with a flat washer profile, the 18-4221 measures 0.39 inches and is finished in white for easy visual identification during service. It is designed to install in place of the original Mercury thrust washer without modification, restoring correct hub spacing and thrust bearing surface on applicable outboards. Every Sierra part is backed by Sierra's customer satisfaction warranty, giving installers confidence in fit and durability for routine prop maintenance or full lower unit rebuilds.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-4221
• Washer Type: Flat
• Material: Rubber
• Metal Type: Alloy Steel
• Finish: Machined
• Color: White
• Size: 0.39 inches
• Dimensions: 0.39 x 0.39 x 0.39 inches
• Weight: 0.23 pounds
• UPC: 030999317681
• OEM Cross-Reference: 13191A1, 75282A1

Fitment

• Mercury 4 & 6 Inline - 75-150 HP

Replaces (OEM)

• Mercury Marine 13191A1
• Mercury Marine 75282A1

Frequently Asked Questions

What does the Sierra 18-4221 thrust washer fit? The 18-4221 fits Mercury 4 & 6 Inline 75-150 HP outboard applications.

Is the Sierra 18-4221 a direct replacement for Mercury 13191A1? Yes, part number 18-4221 is a direct cross-reference for Mercury Marine 13191A1 and 75282A1, installing the same way as the original thrust washer.

What size is this thrust washer? The 18-4221 thrust washer measures 0.39 inches, with overall dimensions of 0.39 x 0.39 x 0.39 inches.

What material is the Sierra 18-4221 made from? This thrust washer is listed with a rubber material composition and a machined finish for a consistent fit against the prop hub.

How much does the 18-4221 thrust washer weigh? It weighs 0.23 pounds.

What color is the Sierra 18-4221 thrust washer? It is finished in white, part number 18-4221.

Is this an OEM or aftermarket part? The 18-4221 is a Sierra-manufactured aftermarket part built to replace Mercury Marine 13191A1 and 75282A1 with equivalent form and function.

What is the difference between a flat thrust washer and other washer types? The 18-4221 is a flat washer type, designed to sit flush against the propeller hub and shaft to absorb axial thrust load, unlike beveled or cupped washer designs.

What is included when I order the 18-4221? Ordering the 18-4221 includes one Sierra thrust washer, part number 18-4221.

Does the Sierra 18-4221 come with a warranty? Yes, the 18-4221 thrust washer is covered under Sierra's customer satisfaction warranty.