Sierra Oil Seal 18-0586, Replaces Chrysler Force 26-99325, Mercury Outboard Powerhead

The Sierra 18-0586 Oil Seal is a precision-machined replacement seal engineered for Mercury outboard powerhead service, covering applications that trace back to Chrysler Force outboard motors now supported under the Mercury Marine parts line. This small but critical component seals against oil and water intrusion at rotating shaft interfaces within the powerhead, helping maintain proper lubrication pressure and preventing contamination that can lead to premature wear or corrosion inside the engine.

Built to Sierra's marine-grade manufacturing standards, this seal is manufactured in Taiwan and machined to tight tolerances so it seats correctly and holds its seal under the vibration, heat cycling, and saltwater exposure typical of outboard powerhead operation. It is sold individually and is sized as a compact internal seal, making it a straightforward drop-in replacement during powerhead rebuilds, seal kit refreshes, or routine maintenance where the original seal has hardened, cracked, or begun leaking.

Because it carries the exact Sierra part number and cross-references directly to the original Chrysler Force equipment number, installers can order with confidence that they are getting a correct fit without needing to cross-check multiple aftermarket alternatives.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-0586
• Product Type: Oil Seal
• OEM Cross Reference: 26-99325 (Chrysler Force)
• Category: Mercury Outboard Powerhead Seals and O-Rings
• Product Dimensions: 0.39 x 0.39 x 0.39 inches
• Package Dimensions: 6.35 cm L x 10.16 cm W x 0.254 cm H
• Weight: 0.01 pounds
• Country of Origin: Taiwan
• Package Quantity: 1

Fitment

This seal is cataloged for Mercury outboard powerhead service and is the correct replacement for Chrysler Force outboard applications using OEM number 26-99325. No specific engine model or year range is specified for this part; confirm your original seal's OEM number matches 26-99325 before ordering.

Replaces (OEM)

• 26-99325 (Chrysler Force)

Frequently Asked Questions

What does the Sierra 18-0586 oil seal replace? Sierra 18-0586 replaces the Chrysler Force OEM number 26-99325, so any powerhead calling for that original equipment number will accept this seal as a direct replacement.

What engine does the 18-0586 seal fit? The 18-0586 seal is cataloged for Mercury outboard powerhead applications that originally used Chrysler Force part 26-99325; no specific engine model or year range is listed, so confirm your existing seal's OEM number matches before ordering.

How much does the 18-0586 oil seal weigh? It weighs 0.01 pounds, reflecting its compact size as an internal powerhead seal.

What are the dimensions of the Sierra 18-0586 seal? The seal itself measures 0.39 x 0.39 x 0.39 inches, and it ships in packaging measuring 6.35 cm L x 10.16 cm W x 0.254 cm H.

Is the 18-0586 an OEM part or an aftermarket replacement? The 18-0586 is a Sierra-manufactured aftermarket seal engineered as a direct cross-reference to Chrysler Force OEM number 26-99325, not an original Chrysler Force or Mercury part.

Where is the Sierra 18-0586 oil seal manufactured? This seal is manufactured in Taiwan under Sierra's marine parts program.

How many seals come in a package of the 18-0586? The 18-0586 is packaged and sold individually, with a package quantity of 1.

What is the difference between the 18-0586 seal and the original Chrysler Force seal? Functionally the 18-0586 is built to match the original Chrysler Force 26-99325 seal for fit and sealing performance; the main difference is that it is produced under the Sierra brand rather than the original Chrysler Force label.

Can the 18-0586 be used in a powerhead rebuild kit? Yes, the 18-0586 oil seal is suited to powerhead rebuild and maintenance work anywhere the Chrysler Force 26-99325 seal is specified.

Does the Sierra 18-0586 seal include installation hardware? No, the 18-0586 is supplied as the seal component only, with a package quantity of 1 and no additional hardware included.

How do I confirm the 18-0586 is the correct seal for my outboard? Check the OEM number stamped on your existing seal or listed in your engine's parts manual against 26-99325; if it matches, Sierra 18-0586 is the correct replacement.