Sierra 18-3802 Head Gasket for Johnson/Evinrude 40 HP and 45 HP Outboard Motors

The Sierra 18-3802 is a marine head gasket built for Johnson/Evinrude outboard motors, sold as a direct-fit replacement for the original equipment gasket on the power head. It seals the joint between the cylinder head and the engine block, maintaining proper compression and preventing coolant or combustion leaks that can lead to overheating or power loss. The gasket is engineered to meet or exceed original equipment quality, making it a reliable choice for a power head rebuild or a routine gasket replacement.

The 18-3802 is finished in white and is fit-specific to the outboard models it covers, so buyers should confirm their engine's horsepower rating and model year before ordering. It is designed as a drop-in match for the factory gasket location, requiring no modification to install. Because head gaskets are wear items exposed to heat cycling and combustion pressure, replacing this gasket during a top-end service helps restore proper sealing and compression on applicable Johnson/Evinrude power heads.

Specifications

• Brand: Sierra
• Manufacturer Part Number: 18-3802
• Category: Evinrude Outboard Power Head Gasket
• Color: White
• Weight: 0.13 pounds
• UPC: 030999316530

Fitment

• Johnson/Evinrude 40 HP outboard, 1984-97
• Johnson/Evinrude 40 HP Commercial outboard, 1994-97
• Johnson/Evinrude 45 HP Commercial outboard, 1985-97

Replaces (OEM)

• 335359
• 327795
• 320658
• GLM 34250
• Mallory 9-63833

Frequently Asked Questions

What is the Sierra 18-3802 head gasket used for? The Sierra 18-3802 seals the joint between the cylinder head and the power head block on Johnson/Evinrude outboard motors, maintaining compression and preventing coolant or combustion leaks.

Which Johnson/Evinrude outboards fit the 18-3802 head gasket? The 18-3802 fits the Johnson/Evinrude 40 HP outboard (1984-97), the 40 HP Commercial outboard (1994-97), and the 45 HP Commercial outboard (1985-97).

Is the 18-3802 gasket a genuine OEM part or aftermarket? The 18-3802 is a Sierra-brand replacement gasket manufactured to meet or exceed original equipment quality; it is not an OEM Johnson/Evinrude branded part but is built as a direct equivalent.

What OEM part numbers does the Sierra 18-3802 replace? The Sierra 18-3802 head gasket cross-references to OEM and interchange numbers 335359, 327795, and 320658, as well as GLM 34250 and Mallory 9-63833.

How much does the 18-3802 head gasket weigh? The Sierra 18-3802 head gasket weighs 0.13 pounds.

What color is the 18-3802 head gasket? This head gasket is white.

Will the 18-3802 fit a Johnson/Evinrude engine outside the listed HP and years? The 18-3802 is fit-specific to the Johnson/Evinrude 40 HP (1984-97), 40 HP Commercial (1994-97), and 45 HP Commercial (1985-97) outboards; buyers should check their engine's HP and model year against these listings before ordering.

How do I know if I need to replace my head gasket? Signs that a power head gasket like the 18-3802 needs replacement include coolant leaks at the cylinder head joint, loss of compression, or overheating on the applicable Johnson/Evinrude outboard.

Is installation of the 18-3802 gasket straightforward? The 18-3802 is a direct-fit replacement gasket for the factory location on covered Johnson/Evinrude power heads, requiring no modification to install during a head or top-end service.

What is the UPC for the Sierra 18-3802 head gasket? The UPC for the Sierra 18-3802 head gasket is 030999316530.