Sierra 18-1117 Pinion Bearing - Replaces OEM 31-42647A1

The Sierra 18-1117 Pinion Bearing is a replacement gearcase pinion bearing built to meet or exceed original equipment quality. It is designed to support the pinion gear inside the lower unit gearcase, allowing smooth rotation and proper gear mesh under load. Made from alloy steel for durability under the heat and pressure generated inside a marine gearcase, the 18-1117 is sized to the same specification as the original part it replaces, so it seats and functions the same as OEM.

This is a small, precision-machined component measuring 0.39 x 0.39 x 0.39 inches, intended to be packed with marine gear lubricant during installation as part of a lower unit rebuild or gearcase service. Because pinion bearings are fit-specific, buyers should confirm the part number against their existing bearing or service manual before ordering, as gearcase hardware varies between models and years.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-1117
• Product Type: Pinion Bearing
• Material: Alloy Steel
• Dimensions: 0.39 x 0.39 x 0.39 inches
• Weight: 0.41 pounds
• Compatible Lubricant: Grease
• UPC: 030999974242

Replaces (OEM)

• 31-42647A1

Frequently Asked Questions

What does the Sierra 18-1117 pinion bearing fit? The Sierra 18-1117 is a direct cross reference for OEM pinion bearing 31-42647A1, so it fits gearcases originally built with that OEM bearing. Because fit is specific to the gearcase, confirm the OEM number on your existing bearing or in your service manual before ordering.

Is 18-1117 the same as OEM part 31-42647A1? Yes, Sierra 18-1117 replaces OEM number 31-42647A1 and is built to meet or exceed the quality of the original equipment part.

What material is the 18-1117 pinion bearing made from? It is made from alloy steel, chosen for its strength and wear resistance under the load and heat inside a marine lower unit gearcase.

What are the dimensions of the Sierra 18-1117 pinion bearing? The bearing measures 0.39 x 0.39 x 0.39 inches, a compact size typical of a pinion gear support bearing.

How much does the Sierra 18-1117 pinion bearing weigh? This bearing weighs 0.41 pounds.

What lubricant should be used with this pinion bearing? The Sierra 18-1117 pinion bearing is designed to run with marine gear grease as its compatible lubricant.

Is the Sierra 18-1117 genuine OEM or aftermarket? It is a Sierra aftermarket replacement bearing engineered to meet or exceed the specification of the original equipment part it replaces, rather than a part sourced from the original engine or drive manufacturer.

What is included when I order the 18-1117? Each order includes one Sierra 18-1117 pinion bearing; it does not include the pinion gear, pinion nut, or other gearcase hardware, which are separate part numbers.

How do I know if I need to replace my pinion bearing? A worn or failing pinion bearing typically shows as gearcase noise, play in the pinion gear, or visible pitting and roughness on the bearing surface during a lower unit teardown; the 18-1117 is used to replace the original bearing at that point.

Does the Sierra 18-1117 come with an installation warranty? The 18-1117 pinion bearing carries a limited warranty as a Sierra replacement part.

What UPC is associated with the Sierra 18-1117 pinion bearing? The UPC for the Sierra 18-1117 pinion bearing is 030999974242.