Sierra 18-0879 Adapter Plate Gasket, Replaces Mercury 27-30501-1

The Sierra 18-0879 Adapter Plate Gasket is a replacement gasket engineered to meet or exceed original equipment quality for Mercury outboard applications. It seals the adapter plate to prevent leaks and maintain proper compression at the mating surface, restoring a tight seal when the original gasket has hardened, torn, or lost its seal after removal for service. As a direct cross-reference to Mercury part number 27-30501-1, it is sized and shaped to install as a drop-in replacement without modification.

This gasket is a single-use component, meaning a new one should be installed any time the adapter plate is removed for maintenance or repair, since reusing a compressed gasket can result in leaks. It ships as a single gasket and is intended for buyers who already know they need this specific Sierra part number or its Mercury OEM equivalent.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-0879
• Product Name: Adapter Plate Gasket
• Category: Mercury Outboard Gaskets
• Quantity per Application: 1
• Weight: 0.07 pounds
• UPC: 030999751621
• GTIN: 00030999751621
• OEM Cross Reference: 27-30501-1

Fitment

Fits applications specified by Mercury OEM part number 27-30501-1.

Replaces (OEM)

• 27-30501-1

Frequently Asked Questions

What does the Sierra 18-0879 Adapter Plate Gasket fit? The Sierra 18-0879 Adapter Plate Gasket is designed as a replacement for Mercury OEM part number 27-30501-1, so it fits the same adapter plate applications that number covers.

Is 18-0879 the same as Mercury 27-30501-1? Yes, Sierra part number 18-0879 is the direct cross-reference to Mercury OEM number 27-30501-1, made to meet or exceed the original equipment part it replaces.

How many gaskets come in one package? One Sierra 18-0879 Adapter Plate Gasket ships per package, matching the quantity of one used per adapter plate application.

How much does the 18-0879 gasket weigh? The Sierra 18-0879 Adapter Plate Gasket weighs 0.07 pounds.

Can the adapter plate gasket be reused after removal? No, a gasket like the Sierra 18-0879 should be replaced with a new one any time the adapter plate is removed, since a used gasket has already been compressed and may no longer seal properly.

Is this a genuine Sierra part or aftermarket? The 18-0879 is a Sierra-branded gasket built to meet or exceed the quality of the original equipment part it replaces, identified by the OEM cross-reference 27-30501-1.

What category of product is the 18-0879 gasket used in? Sierra 18-0879 is listed under Mercury Outboard Gaskets, used to seal the adapter plate on applicable Mercury outboard components.

Does the Sierra 18-0879 gasket require any modification to install? No, the Sierra 18-0879 Adapter Plate Gasket is made as a direct replacement for Mercury 27-30501-1 and installs in place of the original without modification.

What is included when ordering the 18-0879 gasket? Ordering the Sierra 18-0879 includes one Adapter Plate Gasket only.

Why would I need to replace the adapter plate gasket? An adapter plate gasket like the Sierra 18-0879 typically needs replacement after the plate is removed for service, or if the original gasket has failed and is allowing a leak at the adapter plate seal.