330818 Head Gasket for Johnson Evinrude OMC | JLM Marine

Head Gasket for Johnson Evinrude OMC 9.9 10 14 15 HP Outboards

This cylinder head gasket is engineered to fit Johnson Evinrude OMC outboard engines ranging from 9.9 HP to 15 HP, covering models produced between 1974 and 1992. It provides a reliable seal between the cylinder head and block, ensuring optimal compression and preventing coolant or oil leaks in your marine engine.

This aftermarket replacement gasket directly replaces OEM part numbers 330818, 320533, 318914, and 0777389, as well as aftermarket equivalents from Sierra Marine (18-2963) and GLM (34140). It is manufactured to OEM specifications for consistent fitment and performance.

• Ensures proper compression and sealing for reliable engine operation
• Direct replacement for multiple OEM and aftermarket part numbers
• Precision-cut to match original equipment specifications

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

This package includes the following component:

• 1 × Cylinder Head Gasket

Installation Guide

1. Disconnect the battery and allow the engine to cool completely before starting any work.
2. Remove the cylinder head cover and associated hardware, keeping track of all fasteners and their positions.
3. Carefully remove the cylinder head bolts in a crisscross pattern to prevent warping. Lift the cylinder head off the engine block.
4. Thoroughly clean all gasket surfaces on both the cylinder head and engine block, removing all traces of old gasket material and debris. Use a gasket scraper and appropriate solvent.
5. Inspect the cylinder head and block surfaces for warping, cracks, or damage. Address any issues before proceeding.
6. Position the new head gasket on the engine block, ensuring all bolt holes and water passages are properly aligned.
7. Carefully place the cylinder head back onto the block, ensuring the gasket remains properly seated.
8. Install the cylinder head bolts finger-tight in their original positions.
9. Torque the head bolts to the manufacturer's specified torque in the recommended sequence (typically starting from the center and working outward in a crisscross pattern). Consult your service manual for exact torque specifications.
10. Reinstall the cylinder head cover and all associated hardware.
11. Reconnect the battery and check for proper gasket seating by running the engine and inspecting for leaks.
12. Allow the engine to reach operating temperature, then shut it down and recheck torque specifications after cooling (if recommended by the manufacturer).

Troubleshooting & FAQ

Q: How do I confirm this gasket fits my specific Johnson Evinrude engine?
A: Verify that your engine matches one of the compatible models listed: 9.9 HP (1974-92), 10 HP Commercial (1989-90), 14 HP (1988-90), or 15 HP (1974-92). Cross-reference your current gasket or cylinder head with OEM part numbers 330818, 320533, 318914, or 0777389 to ensure correct fitment.

Q: When should I replace my cylinder head gasket?
A: Replace the head gasket if you notice signs of failure such as overheating, white smoke from the exhaust, coolant or oil leaks around the cylinder head, loss of compression, or mixing of oil and coolant. Always install a new gasket when removing the cylinder head for any maintenance or repair.

Q: What are the symptoms of a failing head gasket?
A: Common symptoms include engine overheating, white exhaust smoke, coolant loss without visible external leaks, oil contamination in the coolant (or vice versa), rough idle, loss of power, and visible leaks around the cylinder head area.

Q: Do I need to use any sealant with this gasket?
A: Consult your engine's service manual for specific recommendations. Most modern head gaskets are designed to seal without additional sealant, but some applications may require a thin coat of gasket sealant or following specific manufacturer instructions.

Q: What's the difference between OEM and aftermarket head gaskets?
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.