Sierra Oil Seal 18-2013, Replaces Mercury Marine 26-16977, MerCruiser Alpha I SS and Stern Drive I

The Sierra 18-2013 is a white oil seal built for MerCruiser stern drive applications, sealing against oil and water intrusion at the drive unit. It is a direct cross-reference to Mercury Marine part 26-16977, making it a straightforward replacement when the original seal fails or wears out during routine drive maintenance.

This seal fits the MerCruiser Alpha I SS stern drive (all serial numbers) at the water pump base/upper location, and the MerCruiser Stern Drive Model I (serial number range 1534570 to 1684187) at the water pump location. Confirm your drive model and serial number range before ordering, since stern drive seals are serial-number specific and installing the wrong seal can lead to leaks or premature failure.

The seal is round in shape and finished in white. It ships in compact packaging (2.5 H x 1.3 L x 2.5 W centimeters) and weighs 0.01 pounds, reflecting its small, single-component size. As with any drive seal, replacement is typically done during a water pump service or lower-unit rebuild, and Sierra recommends replacing seals rather than reusing old ones whenever the drive is opened up.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-2013
• Color: White
• Shape: Round
• Weight: 0.01 pounds
• Package Dimensions: 2.5 H x 1.3 L x 2.5 W centimeters
• Country of Origin: Taiwan
• UPC: 030999309594
• OEM Cross Reference: Mercury Marine 26-16977

Fitment

• MerCruiser Alpha I SS Stern Drive (all serial numbers)
• MerCruiser Stern Drive Model I, serial numbers 1534570 to 1684187

Replaces (OEM)

• Mercury Marine 26-16977

Frequently Asked Questions

What does the Sierra 18-2013 oil seal fit? The Sierra 18-2013 fits the MerCruiser Alpha I SS stern drive across all serial numbers, and the MerCruiser Stern Drive Model I within serial number range 1534570 to 1684187.

Is the Sierra 18-2013 the same as Mercury Marine 26-16977? Yes, the Sierra 18-2013 is a direct cross-reference to Mercury Marine part number 26-16977 and can be used in its place.

What color is the 18-2013 oil seal? It is white, and round in shape.

How much does the Sierra 18-2013 oil seal weigh? 0.01 pounds, consistent with its small, single-piece seal design.

Will the 18-2013 seal work on any MerCruiser stern drive? No. It is specific to the MerCruiser Alpha I SS (all serial numbers) and Stern Drive Model I within the 1534570 to 1684187 serial number range; buyers should confirm their drive's serial number before ordering.

Where on the drive does the 18-2013 seal install? On the Alpha I SS it installs at the water pump base/upper location, and on the Stern Drive Model I it installs at the water pump location.

What is included when ordering part 18-2013? One Sierra 18-2013 oil seal is included per unit ordered.

Is Sierra 18-2013 a genuine Sierra part or aftermarket? It is a Sierra-branded oil seal manufactured as a replacement part, cross-referenced to Mercury Marine 26-16977.

What are the package dimensions of the 18-2013 seal? The packaged seal measures 2.5 H x 1.3 L x 2.5 W centimeters.

Where is the Sierra 18-2013 oil seal made? It is made in Taiwan.

When should the 18-2013 oil seal be replaced? This seal is typically replaced during water pump service or a lower-unit rebuild on the applicable MerCruiser stern drive, rather than reusing the old seal.