Sierra 18-2643 Upper Unit Seal Kit for MerCruiser Bravo II X, Bravo III, Bravo III X and Blackhawk Drives

The Sierra 18-2643 Upper Unit Seal Kit is a replacement seal set for the upper gear housing of MerCruiser Bravo II X, Bravo III, Bravo III X, and Blackhawk sterndrive units. This kit addresses the seals responsible for keeping gear lubricant contained and water out of the upper unit, a common service point during routine outdrive maintenance or when diagnosing gear housing leaks. Each kit ships as a complete set (one kit per package) so the seals can be replaced together during a single service interval, rather than sourcing individual seals separately.

Sierra manufactures this kit to meet or exceed the specifications of the original equipment seals it replaces, making it a direct equivalent for the applicable MerCruiser upper units. The kit fits specific serial-number ranges on the Bravo II X, Bravo III, Bravo III X, and Blackhawk drives, so confirming the drive model and serial number before ordering ensures the correct fit. As with all Sierra parts, this kit is backed by Sierra's standard limited warranty.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-2643
• Category: MerCruiser Upper Gear Housing Seal Kit
• Weight: 0.19 pounds
• Color: White
• Shape: Round
• UPC: 030999875204
• Fitment: MerCruiser Bravo II X, Bravo III, Bravo III X, Blackhawk
• OEM Cross Reference: GLM 87480, Mallory 9-74301, Mercruiser 26-16709A1, 27-16709A2

Fitment

• MerCruiser Bravo II X, 2000-2010, serial number M100001 & up
• MerCruiser Bravo III, 1988-2010, serial number B664190 & up
• MerCruiser Bravo III X, 2000-2010, serial number M100001 & up
• MerCruiser Blackhawk, 1994-1995, serial number F186717 & up

Replaces (OEM)

• GLM 87480
• Mallory 9-74301
• Mercruiser 26-16709A1
• 27-16709A2

Frequently Asked Questions

What does the Sierra 18-2643 Upper Unit Seal Kit fit? This kit fits MerCruiser Bravo II X (2000-2010, serial number M100001 & up), Bravo III (1988-2010, serial number B664190 & up), Bravo III X (2000-2010, serial number M100001 & up), and Blackhawk (1994-1995, serial number F186717 & up) upper units.

Is the 18-2643 kit interchangeable with OEM MerCruiser seals? Yes. The Sierra 18-2643 kit is cross-referenced to GLM 87480, Mallory 9-74301, Mercruiser 26-16709A1, and 27-16709A2, and is engineered to meet or exceed the original equipment part it replaces.

How much does the 18-2643 seal kit weigh? The Sierra 18-2643 Upper Unit Seal Kit weighs 0.19 pounds.

What color are the seals in the 18-2643 kit? The seals in the Sierra 18-2643 Upper Unit Seal Kit are white.

What shape are the seals in this kit? The seals included in the 18-2643 kit are round.

Will the 18-2643 kit fit a MerCruiser Bravo I drive? No fitment for a standard Bravo I is specified for the Sierra 18-2643 kit; it applies to Bravo II X, Bravo III, Bravo III X, and Blackhawk drives within the listed serial-number ranges.

How do I know if my drive is within the serial number range for this kit? Check your MerCruiser drive's serial number tag against the ranges for the Sierra 18-2643 kit: M100001 & up for Bravo II X and Bravo III X, B664190 & up for Bravo III, and F186717 & up for Blackhawk.

What is included in the 18-2643 kit? The Sierra 18-2643 Upper Unit Seal Kit includes one complete set of upper gear housing seals for the applicable MerCruiser drives.

Is Sierra 18-2643 a genuine Sierra part or aftermarket? The 18-2643 is a genuine Sierra part, manufactured by Sierra as a direct-fit replacement for the original MerCruiser upper unit seals.

Does the 18-2643 kit come with a warranty? Yes, the Sierra 18-2643 Upper Unit Seal Kit is covered under Sierra's standard limited warranty like all Sierra parts.

What is the UPC for the Sierra 18-2643 kit? The UPC for the Sierra 18-2643 Upper Unit Seal Kit is 030999875204.

When would I need to replace the upper unit seals on a MerCruiser Bravo or Blackhawk drive? The Sierra 18-2643 kit is used when servicing the upper gear housing seals, typically to stop gear lubricant leaks or water intrusion in the upper unit of Bravo II X, Bravo III, Bravo III X, or Blackhawk drives.