Sierra Ball Bearing 18-1155, Replaces Mercury Marine 30-88957A1, 30-88957T, for Counter Rotation Gearcase Applications

This Sierra 18-1155 ball bearing is a gearcase bearing built for counter rotation outboard applications. It is manufactured from alloy steel for durability under the load and rotational demands of a lower unit gearcase, and it is finished in white. The bearing measures 0.39 x 0.39 x 0.39 inches and weighs 0.89 pounds, making it a compact precision component sized for direct fitment into the gearcase housing it was designed for.

As a Sierra-branded part, it is built to serve as a direct equivalent for the OEM Mercury Marine numbers it replaces, giving outboard owners and marine technicians a reliable option when rebuilding or servicing a counter rotation lower unit. Ball bearings like this one support the pinion and gear assembly inside the gearcase, keeping rotating components properly aligned and reducing friction and wear during operation. Because it is designated specifically for counter rotation applications, it is important to confirm that your outboard's gearcase is a counter rotation unit before ordering, since standard rotation gearcases use a different bearing.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-1155
• Bearing Type: Ball Bearing
• Application: Counter Rotation Gearcase Applications
• Material: Alloy Steel
• Color: White
• Item Dimensions: 0.39 x 0.39 x 0.39 inches
• Weight: 0.89 pounds
• UPC: 030999309303
• OEM Cross Reference: 30-88957A1, 30-88957T

Fitment

• For counter rotation gearcase applications

Replaces (OEM)

• Mercury Marine 30-88957A1
• Mercury Marine 30-88957T

Frequently Asked Questions

What is the Sierra 18-1155 bearing used for? The Sierra 18-1155 is a ball bearing used inside an outboard gearcase to support the pinion and gear assembly in counter rotation applications.

Does the 18-1155 fit a standard rotation gearcase? No. The 18-1155 is designated for counter rotation applications, so it should not be used in a standard rotation gearcase; confirm your gearcase rotation before ordering.

What OEM numbers does the 18-1155 replace? It replaces Mercury Marine 30-88957A1 and 30-88957T, so either OEM number can be cross-referenced to Sierra part 18-1155.

What material is the 18-1155 ball bearing made from? It is made from alloy steel, giving it the strength needed to handle continuous rotation and load inside the gearcase.

What size is the Sierra 18-1155 bearing? The 18-1155 measures 0.39 x 0.39 x 0.39 inches, a compact size built to fit precisely into its designated gearcase bore.

How much does the 18-1155 bearing weigh? The Sierra 18-1155 ball bearing weighs 0.89 pounds.

Is the Sierra 18-1155 a genuine Sierra part or a knockoff? It is a genuine Sierra International branded ball bearing, part number 18-1155, not a generic substitute.

What color is the 18-1155 bearing? The 18-1155 has a white finish.

What is included when I order the 18-1155? Each order of the Sierra 18-1155 includes one ball bearing unit.

Can the 18-1155 be identified by its UPC? Yes, the Sierra 18-1155 ball bearing carries UPC 030999309303 for identification and ordering.

What lubricant is compatible with the 18-1155 bearing? The 18-1155 ball bearing is designed for use with grease as its compatible lubricant.