Why Choose the Sierra 18-3802 Head Gasket for Your OMC Engine?

When maintaining a classic OMC outboard, finding a reliable head gasket that seals perfectly under high heat and pressure is crucial. The Sierra 18-3802 steps in as a direct replacement for the original OMC 3327795, engineered to restore compression and prevent coolant leaks in demanding marine environments. Crafted from multi-layer steel with precise port matching, it handles the rigors of saltwater exposure and high-RPM operation better than many generics.

Boat owners swear by Sierra parts for their consistent performance on the water. This gasket isn't just a patch—it's a rebuild essential that extends engine life, ensuring smooth power delivery from your Johnson's loop-charged powerhead.

Perfect Fit for Popular OMC Models

Designed specifically for OMC's inline 3-cylinder engines, the 18-3802 bolts right into models from the late '80s through early 2000s. It matches the factory specs for 90HP to 120HP V4 powerheads, including crossflow and loop-scavenged designs common in Johnson and Evinrude outboards.

• Seals combustion chambers without warping
• Resists corrosion from ethanol-blended fuels
• Compatible with OEM torque sequences

Before installing, double-check your engine's serial number plate—it's a game-changer for DIY mechanics tackling top-end refreshes.

Key Features That Set It Apart

Sierra prioritizes durability in every layer. Here's what makes the 18-3802 stand out:

• MLS Construction: Multi-layer steel for superior sealing and reusability in some rebuilds.
• Precision Fire Ring: Contains combustion gases, reducing blow-by and oil contamination.
• Anti-Micro Pitting: Edges treated to fend off electrolysis in brackish water.
• Exact OEM Dimensions: Matches bore, stroke, and coolant passage layouts flawlessly.

Unlike flimsy paper gaskets that delaminate after a season, this one thrives on repeated heat cycles, keeping your midrange punch intact.

Step-by-Step Installation Insights

Swapping a head gasket on an OMC isn't rocket science, but attention to detail pays off. Here's a pro tip sequence:

1. Drain coolant and remove the head—label all hoses and wires.
2. Clean deck surfaces meticulously; use a plastic scraper to avoid gouges.
3. Apply thin sealant to water passages only—never on the combustion side.
4. Torque in stages: 22 ft-lbs, then 33, finally 40 per the factory pattern (center out).
5. Run a cold cycle, check for leaks, then break in at 3000 RPM.

Pro mechanics note: Always replace head bolts if stretched—pairing with new ones maximizes longevity.

Maintenance Tips to Maximize Longevity

A great gasket shines with proper care. Monitor compression every 100 hours, flush cooling passages post-saltwater runs, and switch to non-ethanol fuel if possible. Overheating is the number one gasket killer—keep that impeller fresh.

"Installed on my '95 Evinrude 112. Paired with a valve job, it's running like new after 50 hours." — Experienced OMC enthusiast

Regular checks catch issues early, saving you from a full powerhead teardown.

Frequently Asked Questions