Sierra 18-2945-9 Drain Screw Gasket for 3/8-16 Drain and Fill Screws, Replaces 307552, Pack of 2

The Sierra 18-2945-9 Drain Screw Gasket is a replacement gasket sized for the 3/8-16 drain and fill screw found on most lower units and sea water pumps, including the drain/fill screw used on all MerCruiser sterndrives and most Mercury/Mariner outboards. It is sold as a pack of 2 gaskets, giving you a matched set for a complete drain/fill screw service without needing to source individual pieces separately.

Built from stainless steel with a machined finish, this gasket is designed to create a reliable seal against water and lubricant leakage at the drain screw location, helping protect the lower unit or sea water pump from moisture intrusion and gear lube loss. Because the fit is specific to the 3/8-16 drain screw size, it is important to confirm your screw and housing match this specification before ordering.

This gasket carries the Sierra part number 18-2945-9 and directly replaces the original equipment gasket bearing the number 307552, so it is a straightforward drop-in replacement during routine gear lube changes or drain screw servicing.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-2945-9
• Package Quantity: Pack of 2
• Material: Stainless Steel
• Finish: Machined Stainless Steel
• Fastener Size: 3/8-16
• Outside Diameter: 4 Inches
• Item Dimensions: 4 x 4 x 1 inches
• Compatible Groove Diameter: 0.38 Inches
• Weight: 0.01 pounds
• UPC: 808282164324

Fitment

• Used with the 3/8-16 drain/fill screw found on all MerCruiser sterndrives and most Mercury/Mariner outboards
• Fits most lower units and sea water pumps

Replaces (OEM)

• 307552

Frequently Asked Questions

What size drain screw does the Sierra 18-2945-9 gasket fit? The Sierra 18-2945-9 Drain Screw Gasket is sized for a 3/8-16 drain and fill screw, the size found on all MerCruiser sterndrives and most Mercury/Mariner outboards.

How many gaskets come in a pack? This listing is for the Sierra 18-2945-9 gasket sold as a pack of 2, giving you a matched pair for a drain and fill screw service.

What OEM part number does this gasket replace? Part number 18-2945-9 replaces OEM number 307552.

What material is the 18-2945-9 gasket made from? Stainless steel with a machined finish, chosen for corrosion resistance in marine drain and fill screw applications.

Will this gasket fit my lower unit or sea water pump? Yes, as long as the drain or fill screw uses the 3/8-16 thread size, since the Sierra 18-2945-9 gasket is designed to fit most lower units and sea water pumps with that screw size.

Is the 18-2945-9 gasket compatible with MerCruiser sterndrives? It is compatible with all MerCruiser sterndrives that use the 3/8-16 drain/fill screw, along with most Mercury/Mariner outboards.

How do I install the drain screw gasket? Remove the old drain or fill screw and gasket, place a new Sierra 18-2945-9 gasket on the screw, and reinstall the screw into the lower unit or sea water pump housing to seal the drain point.

What are the outer dimensions of this gasket? The Sierra 18-2945-9 gasket has an outside diameter of 4 inches and item dimensions of 4 x 4 x 1 inches, with a compatible groove diameter of 0.38 inches.

How much does this part weigh? The Sierra 18-2945-9 Drain Screw Gasket pack weighs 0.01 pounds.

Is this a genuine Sierra part or an aftermarket copy? It is a Sierra branded part, number 18-2945-9, manufactured to meet or exceed the specification of the original drain screw gasket it replaces.

Can I use this gasket on Mercury or Mariner outboards? Yes, the 3/8-16 drain/fill screw gasket configuration used on the Sierra 18-2945-9 fits most Mercury and Mariner outboards.

What is included when I order this part? Ordering part number 18-2945-9 gets you a pack of 2 stainless steel drain screw gaskets, sized for a 3/8-16 drain or fill screw.