Sierra Drain/Fill Plug Washer 18-4248-9, Replaces 311598, Plastic, Pack of 5

The Sierra 18-4248-9 is a plastic drain/fill plug washer sold in a package of 5, sized for use with outboard and sterndrive gearcases during routine gear lube service. It seats under the drain and fill plugs to create a reliable seal against gear lube leakage, preventing seepage past the plug threads as the gearcase heats and cools through normal operation. Being plastic rather than metal, the washer resists corrosion in the wet, salt-exposed environment around a lower unit drain plug, and it is inexpensive enough to replace as a matter of routine every time the gear lube is changed, which is the standard practice for sealing washers of this type. This part is designed to be used with the Sierra 18-2387 drain screw, pairing the correct washer to the correct screw for a proper seal at the drain point. Because it directly replaces OEM number 311598, it is a straightforward swap for anyone servicing a gearcase that originally used that factory washer. Being sold in a pack of 5 lets a technician or boat owner keep spares on hand, since a fresh washer at every fluid change is the simplest way to avoid a plug that will not seal.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-4248-9
• Product Name: Drain/Fill Plug Washer
• Material: Plastic
• Package Quantity: Pack of 5
• Weight: 0.01 pounds
• Used With: 18-2387 Drain Screw
• OEM Cross-Reference: 311598

Fitment

• Designed for use with the Sierra 18-2387 drain screw at the gearcase drain/fill point.

Replaces (OEM)

• 311598

Frequently Asked Questions

What is the Sierra 18-4248-9 washer made of? It is made of plastic, which resists corrosion better than a metal washer in the wet environment around a gearcase drain plug.

How many washers come in a package of the 18-4248-9? The 18-4248-9 is sold in a package of 5 plastic drain/fill plug washers.

What OEM part number does the 18-4248-9 washer replace? This washer replaces OEM number 311598.

What drain screw is the 18-4248-9 washer used with? It is used with the Sierra 18-2387 drain screw to seal the gearcase drain/fill point.

Can I use the 18-4248-9 washer with a different drain screw? The 18-4248-9 washer is specified for use with the 18-2387 drain screw; that is the pairing it is designed to seal against.

How often should the drain/fill plug washer be replaced? A fresh washer like the Sierra 18-4248-9 is typically installed every time the gear lube is drained and refilled, since reusing an old sealing washer risks a leak at the plug.

Is the Sierra 18-4248-9 an OEM or aftermarket part? The 18-4248-9 is a Sierra-brand replacement washer that cross-references to OEM number 311598, so it is an aftermarket equivalent rather than a factory-branded part.

How much does the 18-4248-9 washer weigh? The Sierra 18-4248-9 drain/fill plug washer weighs 0.01 pounds.

What happens if I do not replace the drain plug washer? Reusing a worn washer under the drain or fill plug can allow gear lube to seep out or water to seep in, which is why a new 18-4248-9 washer is recommended at each service.

Is the 18-4248-9 washer sold individually or in a set? It is sold as a package of 5 washers, not individually.