Sierra 18-2831-9 Thermostat Cover Gasket, Replaces 27-475901 and 27-47590, 4 Cylinder Engines, Pack of 2

The Sierra 18-2831-9 Thermostat Cover Gasket seals the thermostat housing on 4 cylinder marine engines, preventing coolant leaks at the thermostat cover joint. Each package contains 2 gaskets, so a spare is on hand for a future service or so both sides of a twin-engine boat can be serviced from a single purchase. The gasket is manufactured by Sierra to replace OEM part numbers 27-475901 and 27-47590, giving boat owners a direct-fit option for thermostat housing service without sourcing the original equipment part. Sierra parts are built to meet or exceed the specifications of the original equipment they replace, making this gasket a straightforward choice when doing a thermostat swap, a cooling system inspection, or general engine maintenance. Because a worn or damaged thermostat cover gasket is a common source of small coolant leaks and overheating complaints, keeping a correct-fit gasket like the 18-2831-9 on hand simplifies routine thermostat service. This is a lightweight, low-cost component but proper fit and sealing are essential to keeping the cooling system airtight and leak-free.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-2831-9
• Product Type: Thermostat Cover Gasket
• Package Quantity: Pack of 2
• Engine Fitment: 4 Cylinder
• OEM Cross Reference: 27-475901, 27-47590
• UPC: 808282163389
• GTIN: 00808282163389
• Weight: 0.03 pounds

Fitment

• 4 Cylinder engines

Replaces (OEM)

• 27-475901
• 27-47590

Frequently Asked Questions

What does the Sierra 18-2831-9 gasket fit? The Sierra 18-2831-9 Thermostat Cover Gasket is designed for 4 cylinder marine engines and seals the thermostat housing cover.

How many gaskets come in a package? Part number 18-2831-9 is sold in a package of 2 gaskets, giving you a spare for a future thermostat service.

What OEM part numbers does this gasket replace? It replaces OEM numbers 27-475901 and 27-47590, so either of those part numbers can be cross-referenced to the Sierra 18-2831-9.

Is the Sierra 18-2831-9 a genuine OEM part or an aftermarket replacement? It is a Sierra-manufactured aftermarket gasket built to meet or exceed the specifications of the original 27-475901 and 27-47590 OEM parts it replaces.

How much does the gasket weigh? Each package of the 18-2831-9 Thermostat Cover Gasket weighs 0.03 pounds.

When should the thermostat cover gasket be replaced? Replace the gasket whenever the thermostat housing is opened for service or if coolant seepage is visible at the thermostat cover joint; the 18-2831-9 is sized for that resealing job on 4 cylinder engines.

Can I use one gasket from the pack and save the other? Yes, the 18-2831-9 is sold as a pack of 2, so one gasket can be installed now and the second kept as a spare for the next service.

Does the 18-2831-9 gasket require any sealant to install? The dossier does not specify a sealant requirement for the 18-2831-9; follow your engine's thermostat housing service procedure when installing.

Is this the same gasket used on 6 cylinder engines? No, the Sierra 18-2831-9 is specified for 4 cylinder engines; a different Sierra part number covers 4 and 6 cylinder applications with a different OEM cross-reference.

What is the UPC for the Sierra 18-2831-9? The UPC for this thermostat cover gasket package is 808282163389.