Sierra 18-0577 Carrier Oil Seal Assembly, Replaces Mercruiser 66081A2, for Alpha One and Gen II Stern Drives

The Sierra 18-0577 Carrier Oil Seal Assembly is a replacement seal for the upper gear housing carrier on MerCruiser stern drive units. It fits the 888/228/250/260 series, the R and MR designations, Alpha One (including Alpha One SS and the counter-rotating CR versions), and Alpha One Gen II drives (including the CR versions). This seal assembly is a direct cross to Mercruiser 66081A2, 35993A1, 66081A1, and 66081A4, as well as GLM 28370 and Mallory 9-78100, so it can be used to service drives originally fitted with any of those parts.

The carrier oil seal keeps gear lube contained within the upper gear housing while preventing water intrusion at the drive shaft carrier, protecting the gear set from contamination and low-lubricant wear. It is typically installed as part of a routine upper gear housing seal kit service or whenever the carrier bearing/seal area is opened up for repair. Sierra manufactures this part to meet or exceed the specification of the original equipment it replaces, and it is backed by Sierra's standard customer satisfaction warranty.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-0577
• Product Name: Carrier Oil Seal Assembly
• Category: Mercruiser Upper Gear Housing Seal Kits
• Weight: 0.2 pounds
• Unit Count: 1
• UPC: 030999973986
• GTIN: 00030999973986
• OEM Cross-Reference: GLM 28370, Mallory 9-78100, Mercruiser 66081A2, 35993A1, 66081A1, 66081A4

Fitment

• MerCruiser 888/228/250/260, 1977-1982
• MerCruiser R, 1983
• MerCruiser MR Alpha One, 1984-1990
• MerCruiser MR Alpha One (CR), 1984-1990
• MerCruiser Alpha One SS, 1986-1989
• MerCruiser Alpha One Gen II, 1991-1995
• MerCruiser Alpha One Gen II (CR), 1991-1995
• MerCruiser Alpha One Gen II, 1996-1997
• MerCruiser Alpha One Gen II (CR), 1996-2010

Replaces (OEM)

• GLM 28370
• Mallory 9-78100
• Mercruiser 66081A2
• Mercruiser 35993A1
• Mercruiser 66081A1
• Mercruiser 66081A4

Frequently Asked Questions

What does the Sierra 18-0577 Carrier Oil Seal Assembly fit? It fits MerCruiser stern drive units including the 888/228/250/260 series (1977-1982), the R (1983) and MR (1984-1990) designations, Alpha One and Alpha One SS (1986-1989), and Alpha One Gen II drives (1991-2010), including the counter-rotating (CR) versions.

Is the 18-0577 seal a genuine OEM part or aftermarket? Sierra 18-0577 is a Sierra-manufactured replacement part, built to meet or exceed the original equipment specification for the Mercruiser carrier oil seal it replaces.

What OEM part numbers does Sierra 18-0577 cross to? This carrier oil seal assembly is interchangeable with Mercruiser 66081A2, 35993A1, 66081A1, and 66081A4, as well as GLM 28370 and Mallory 9-78100.

Does the 18-0577 fit both Alpha One and Alpha One Gen II drives? Yes, the 18-0577 carrier oil seal is used across Alpha One (1984-1990), Alpha One SS (1986-1989), and Alpha One Gen II (1991-2010) MerCruiser stern drives, including the CR variants.

How much does the Sierra 18-0577 weigh? The Sierra 18-0577 Carrier Oil Seal Assembly weighs 0.2 pounds.

How many pieces come in the 18-0577 package? The Sierra 18-0577 ships as a single carrier oil seal assembly, unit count of 1.

What is the function of the carrier oil seal on a stern drive? The carrier oil seal seated in the upper gear housing keeps gear lubricant contained around the drive shaft carrier while blocking water intrusion, protecting the gear set from contamination and lubricant loss.

When should the carrier oil seal be replaced? The 18-0577 carrier oil seal is typically replaced during a upper gear housing seal service, or any time the carrier bearing and seal area is opened up for repair or found to be leaking gear lube.

Does the 18-0577 fit the MerCruiser 888/228/250/260 models? Yes, the Sierra 18-0577 is listed for the MerCruiser 888/228/250/260 series produced 1977-1982.

Is the 18-0577 covered by a warranty? Sierra 18-0577, like other Sierra parts, is covered under Sierra's standard customer satisfaction warranty.