Sierra Upper Unit Casing Gasket 18-99164 for Yamaha Outboard Gearcase

The Sierra Upper Unit Casing Gasket, part number 18-99164, is a replacement gasket designed for use in the upper unit casing of Yamaha outboard gearcase and drive systems. This gasket seals the mating surfaces of the upper casing to help maintain proper lubrication levels and prevent water intrusion into the gearcase, both of which are essential to protecting internal gears and bearings from corrosion and premature wear. Installing a fresh gasket whenever the upper casing is opened for service, such as during a gear lube change, seal replacement, or gearcase inspection, helps ensure a reliable seal is restored rather than reusing a compressed or damaged original gasket. Sierra manufactures this gasket for the marine aftermarket as a direct fit for the Yamaha outboard gearcase and drive parts application it is designated for. Keeping a gasket like this on hand is useful for routine maintenance and repair work on outboard lower units, since a compromised gasket can lead to lubricant loss or water contamination that damages gearcase components.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-99164
• Product Name: Upper Unit Casing Gasket
• Application: Yamaha Outboard Gearcase & Drive Parts
• Weight: 0.05 pounds
• Package Dimensions: 4 x 4 x 0.5 inches
• UPC: 808282385781

Fitment

• Yamaha outboard gearcase and drive systems (upper unit casing)

Frequently Asked Questions

What is the Sierra 18-99164 gasket used for? Sierra part number 18-99164 is an upper unit casing gasket used to seal the upper casing of a Yamaha outboard gearcase and drive system, helping keep gear lubricant in and water out.

Does the 18-99164 gasket fit Yamaha outboards? Yes, the 18-99164 upper unit casing gasket is designated for Yamaha outboard gearcase and drive parts applications.

How much does the 18-99164 gasket weigh? The Sierra Upper Unit Casing Gasket, part number 18-99164, weighs 0.05 pounds.

What are the package dimensions of this gasket? The 18-99164 gasket ships in packaging measuring 4 x 4 x 0.5 inches.

Is 18-99164 a genuine Sierra part number? Yes, 18-99164 is the Sierra manufacturer part number for this Upper Unit Casing Gasket, not a supplier or retailer code.

When should the upper unit casing gasket be replaced? This gasket should be replaced any time the upper casing on the Yamaha outboard gearcase is opened for service, such as during a gear lube change or gearcase inspection, since a reused gasket may not seal properly.

What happens if the upper casing gasket fails or is not replaced? A worn or damaged upper unit casing gasket like 18-99164 can allow gear lubricant to leak out or water to enter the gearcase, both of which can lead to corrosion and damage to internal gears and bearings.

What is included when ordering part 18-99164? Ordering Sierra 18-99164 includes one Upper Unit Casing Gasket sized for the Yamaha outboard gearcase upper casing application.

Is the 18-99164 gasket an OEM or aftermarket part? The 18-99164 Upper Unit Casing Gasket is manufactured by Sierra for the marine aftermarket as a replacement part for Yamaha outboard gearcase applications.

Can this gasket be reused after removal? No, gaskets such as the Sierra 18-99164 are designed for one-time use; once the upper casing is disassembled, a new gasket should be installed to ensure a proper seal.