329103 Head Gasket for Johnson Evinrude OMC 5HP 5.5HP 6HP | JLM Marine

Head Gasket for Johnson Evinrude OMC 5HP 5.5HP 6HP

This cylinder head gasket is designed for Johnson Evinrude OMC outboard engines rated at 5HP, 5.5HP, and 6HP. It provides a reliable seal between the cylinder head and engine block, ensuring optimal compression and preventing coolant or combustion gas leaks.

This aftermarket replacement directly replaces OEM part numbers 306204, 329103, and 777397, as well as GLM 33830 and Sierra 18-2961, offering broad compatibility across multiple model years from 1959 through 1979.

• Fits Johnson Evinrude OMC 5HP (1965-68), 5.5HP (1959-64), and 6HP (1965-79) outboards
• Direct replacement for multiple OEM and aftermarket part numbers
• Single gasket included per package

Part Number Cross-Reference

Use this table to confirm equivalent part numbers across OEM and aftermarket brands.

Compatible Engine Models

Confirm your engine model/year in the table below. For Johnson/Evinrude owners, here's a guide to help you identify your engine's serial/model: Johnson Serial Number Guide.

Technical Specifications

Package Contents

Each package includes:

• 1 × Cylinder Head Gasket

Installation Guide

1. Disconnect the spark plug wire to prevent accidental starting during service.
2. Remove the cylinder head bolts in a crisscross pattern to avoid warping the head.
3. Carefully lift off the cylinder head and set it on a clean work surface.
4. Thoroughly clean both the cylinder head and engine block mating surfaces, removing all traces of the old gasket material and carbon deposits.
5. Inspect the cylinder head for cracks, warping, or damage; resurface or replace if necessary.
6. Position the new head gasket on the engine block, ensuring all bolt holes and coolant passages align correctly.
7. Carefully lower the cylinder head onto the gasket, avoiding any shifting that could damage the seal.
8. Hand-thread all cylinder head bolts to prevent cross-threading.
9. Torque the head bolts to the manufacturer's specification in a crisscross sequence, working from the center outward.
10. Reconnect the spark plug wire and any other components removed during disassembly.
11. Start the engine and check for leaks around the head gasket area.
12. Allow the engine to reach operating temperature, then recheck torque specifications after the first few hours of use.

Troubleshooting & FAQ

Q: How do I confirm this gasket fits my specific Johnson or Evinrude engine?
A: Cross-reference your engine's HP rating and year with the compatibility table above. This gasket fits 5HP (1965-68), 5.5HP (1959-64), and 6HP (1965-79) models. You can also verify by matching your original OEM part number (306204, 329103, or 777397) with those listed.

Q: How often should I replace the cylinder head gasket?
A: Head gaskets should be replaced whenever the cylinder head is removed for service, or immediately if you notice compression loss, coolant leaks, or overheating. Regular maintenance intervals vary, but inspect annually for engines used frequently.

Q: What are the signs that my head gasket is failing?
A: Common symptoms include overheating, loss of power, visible coolant leaks around the cylinder head, white smoke from the exhaust, or oil contamination in the cooling system. If you observe any of these, inspect and replace the gasket promptly.

Q: Do I need to apply sealant to this gasket during installation?
A: Most modern head gaskets are designed to seal without additional sealant. Check your engine's service manual for specific recommendations. Over-application of sealant can actually cause sealing issues or block coolant passages.

Q: Is this OEM or aftermarket?
A: This listing is an aftermarket replacement part (not an OEM component). We build to OEM specifications using comparable-grade materials. Production is done in an ISO9002-certified facility, and each batch is inspected for consistent performance.

Q: How fast do you ship and how much does it cost?
A: We offer fast global shipping—typically 5–15 days worldwide—and standard shipping is free. Expedited options are available at checkout depending on your location.

Q: What is your warranty and return policy?
A: This product includes a 1-year warranty against manufacturing defects under normal use. If something goes wrong, contact our support team with your order details. Returns are accepted within our standard return window (unused & in original condition); please see our policy page or reach out for instructions.

Important Notes

• Verify that the product images and specifications match your original part. If discrepancies exist—even if your model is listed—do not proceed with the purchase.
• This product is an aftermarket replacement part and is not an OEM component.
• Professional installation is recommended to ensure safety and optimal performance.

Why Choose JLM MARINE?

• Quality Assured: As a trusted manufacturer for over 20 years, we supply top marine brands globally.
• Fast Global Shipping: Free delivery worldwide in 5–15 days.
• Direct from Manufacturer: Competitive pricing without compromising quality.