Sierra 18-2387 Lower Unit Drain/Fill Screw, Alloy Steel, Machined Finish

The Sierra 18-2387 is a lower unit drain/fill screw built for outboard and sterndrive gearcase service, where a dependable seal against gear lube leakage is essential. Machined from alloy steel, it is engineered to meet or exceed original equipment quality so it can be trusted for routine gearcase maintenance, gear lube changes, or as a replacement when an existing drain or fill screw is stripped, corroded, or lost. The machined finish gives the threads a consistent, precise engagement in the gearcase housing, helping the screw seat properly and resist rounding during removal and reinstallation.

This screw is designed to be used together with a matching plastic washer that provides the actual sealing surface against the gearcase housing; the washer is sold as its own separate part and is not included with the 18-2387 screw. Keeping the correct washer paired with this screw helps maintain a tight, leak-free seal at every gear lube service.

Sierra supplies this part as a single-count item, packaged for easy identification by its part number, making it simple for boat owners and marine technicians to keep a spare drain/fill screw on hand for scheduled maintenance or emergency repairs.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-2387
• Material: Alloy Steel
• Exterior Finish: Machined
• Item Type: Lower Unit Drain/Fill Screw
• Weight: 0.03 pounds
• UPC: 808282239459
• Quantity: 1 screw per pack

Frequently Asked Questions

What is the Sierra 18-2387? It is a lower unit drain/fill screw made of alloy steel with a machined finish, used to seal the gearcase drain or fill hole on a marine lower unit.

What material is the 18-2387 drain screw made of? Alloy steel with a machined exterior finish, giving the threads a precise, consistent fit in the gearcase housing.

How much does the Sierra 18-2387 weigh? The Sierra 18-2387 weighs 0.03 pounds.

Does the 18-2387 come with a sealing washer? No. The 18-2387 screw does not include the plastic washer used with it; the washer that pairs with this drain screw is sold as a separate part.

Why do I need a washer with this screw? The plastic washer used with the 18-2387 drain screw provides the sealing surface against the gearcase housing, so pairing a washer with the screw is necessary for a leak-free seal during gear lube service.

How many screws come in a package of the 18-2387? The Sierra 18-2387 is packaged as a single screw, one count per unit.

Is the Sierra 18-2387 an OEM-quality replacement? Yes, the 18-2387 is manufactured to meet or exceed original equipment quality standards for a lower unit drain/fill screw.

What is the UPC for the Sierra 18-2387? The UPC for the Sierra 18-2387 lower unit drain/fill screw is 808282239459.

What is this screw used for? The 18-2387 is used at the drain or fill point of a marine lower unit gearcase, typically during gear lube changes or as a replacement for a damaged screw.

What finish does the 18-2387 have? It has a machined alloy steel finish rather than a coated or plated surface.