Sierra 18-2964 Head Gasket for Johnson/Evinrude 150 HP (1973-91) and 155 HP Commercial (1984-92) Outboards

The Sierra 18-2964 is a head gasket built for Johnson/Evinrude outboard power heads, designed to seal the cylinder head against the engine block and maintain proper compression, coolant flow, and combustion sealing. It fits Johnson/Evinrude 150 HP outboards from 1973-91 as well as the 155 HP Commercial model from 1984-92. Each package contains one gasket, engineered to meet or exceed the sealing performance of the original equipment part it replaces. Because a head gasket sits at a critical sealing point between the cylinder head and block, using a properly sized replacement like the 18-2964 helps prevent compression loss, coolant leakage, and exhaust blow-by that can follow from a worn or damaged factory gasket. This is a direct-fit replacement part rather than a universal or trimmable gasket, so it is matched to the specific power head applications listed below. Boat owners and marine technicians rebuilding or servicing a Johnson/Evinrude power head on one of these applications can use the 18-2964 as a like-for-like replacement during a head gasket job.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-2964
• UPC: 030999314635
• Product Type: Head Gasket
• Category: Evinrude Outboard Power Head Gaskets
• Fitment: Johnson/Evinrude 150 HP, 1973-91
• Fitment: Johnson/Evinrude 155 HP Commercial, 1984-92
• OEM Cross Reference: 320745, 335360, 766779, GLM 33870, Mallory 9-63829
• Weight: 0.17 pounds
• Product Dimensions: 0.39 x 0.39 x 0.39 inches
• Package Quantity: 1 gasket per package

Fitment

• Johnson/Evinrude 150 HP, 1973-91
• Johnson/Evinrude 155 HP Commercial, 1984-92

Replaces (OEM)

• 320745
• 335360
• 766779
• GLM 33870
• Mallory 9-63829

Frequently Asked Questions

What engines does the Sierra 18-2964 head gasket fit? The 18-2964 is built for Johnson/Evinrude outboards, specifically the 150 HP model from 1973-91 and the 155 HP Commercial model from 1984-92.

Is the 18-2964 a direct OEM replacement? Yes, it is a direct-fit replacement engineered to meet or exceed the sealing performance of the original head gasket it replaces on the applicable Johnson/Evinrude power heads.

What OEM part numbers does the 18-2964 cross-reference to? It cross-references to OEM numbers 320745, 335360, and 766779, as well as GLM 33870 and Mallory 9-63829.

How much does the 18-2964 head gasket weigh? It weighs 0.17 pounds.

What are the dimensions of the Sierra 18-2964? The gasket measures 0.39 x 0.39 x 0.39 inches as packaged.

How many gaskets come in one package of the 18-2964? One head gasket is included per package.

Will the 18-2964 fit any Johnson/Evinrude outboard regardless of horsepower? No, it is specific to the 150 HP (1973-91) and 155 HP Commercial (1984-92) Johnson/Evinrude power heads listed for this part number, not a universal fit.

Is the Sierra 18-2964 genuine Sierra or a generic aftermarket gasket? It is a genuine Sierra-branded part, part number 18-2964, made to replace the factory head gasket on the specified Johnson/Evinrude applications.

Can the 18-2964 be used as a Mallory 9-63829 replacement? Yes, the 18-2964 cross-references directly to Mallory 9-63829 along with the other listed OEM numbers.

When should a head gasket like the 18-2964 be replaced? A head gasket should be replaced any time the cylinder head is removed for service, or if it shows signs of compression loss, coolant leakage, or exhaust blow-by, using a matched part like the 18-2964 for the applicable Johnson/Evinrude engine.