Sierra 18-2946 Head Gasket - Replaces 16.50-00204 for GM 181 CID (3.0L) Marine Engines

The Sierra 18-2946 Head Gasket is a marine-grade replacement gasket engineered for GM 181 CID (3.0L) engines used in stern drive and inboard marine applications. It is designed to seal the mating surface between the cylinder head and engine block, maintaining proper compression, coolant containment, and oil control under the sustained heat and vibration cycles typical of marine service. Using a gasket built specifically for the marine environment, rather than an automotive substitute, helps ensure a reliable, long-term seal against the corrosion and thermal stress that saltwater and freshwater cooling systems introduce.

The 18-2946 is a direct fit for GM 181 CID (3.0L) engines and is a cross-reference match for the OEM 16.50-00204 gasket, allowing it to be installed as a like-for-like replacement during a head gasket service, engine rebuild, or head removal for valve or manifold work. Each Sierra product is built to meet or exceed the performance of the original equipment part it replaces, giving boat owners and marine technicians a dependable option when the factory gasket has failed or the engine is being serviced.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-2946
• Replaces (OEM Cross-Reference): 16.50-00204
• Fitment: GM 181 CID Engine (3.0L)
• Weight: 0.61 pounds
• Color: White
• Unit Count: 1

Fitment

• GM 181 CID Engine (3.0L)

Replaces (OEM)

• 16.50-00204

Frequently Asked Questions

What engine does the Sierra 18-2946 head gasket fit? The 18-2946 head gasket is designed for GM 181 CID (3.0L) marine engines.

Is the 18-2946 a direct OEM replacement? Yes, it directly replaces OEM part number 16.50-00204 and is built to meet or exceed the original equipment part's performance.

How much does the 18-2946 head gasket weigh? It weighs 0.61 pounds.

What color is the Sierra 18-2946 head gasket? It is white.

How many gaskets come in a package of the 18-2946? The 18-2946 is sold as a single-unit head gasket, with a unit count of 1.

Can the 18-2946 be used on other GM engine sizes like the 305 or 350 CID? No, the 18-2946 is specified for GM 181 CID (3.0L) engines; larger GM 305/350 and 454 CID engines use different Sierra head gasket part numbers.

Does the 18-2946 require any special gasket sealant during installation? A dedicated gasket sealant is recommended for proper installation of the 18-2946, though the sealant itself is a separate product.

Is the 18-2946 suitable for both engine rebuilds and single head gasket replacement jobs? Yes, this Sierra head gasket can be used for a full engine rebuild or a standalone head gasket replacement on a GM 181 CID (3.0L) engine.

What OEM part number does the 18-2946 cross-reference to? It cross-references to OEM number 16.50-00204.

Is the Sierra 18-2946 a genuine OEM part or an aftermarket equivalent? The 18-2946 is a Sierra-manufactured aftermarket gasket engineered to meet or exceed the performance of the original 16.50-00204 OEM gasket it replaces.