6H4-11181-00 Cylinder Head Gasket for Yamaha 40HP 50HP Pro 50 | JLM Marine

Cylinder Head Gasket for Yamaha 40HP 50HP Pro 50 Outboard Engines

This cylinder head gasket is designed to fit Yamaha 40HP and 50HP (including Pro 50) 2-stroke outboard engines manufactured between 1984 and 1994. It provides a reliable seal between the cylinder head and engine block, preventing compression loss and coolant leaks.

This aftermarket replacement directly replaces Yamaha OEM part numbers 6H4-11181-00, 6H4-11181-A0-00, 6H4-11181-A1-00, 6H4-11181-A2-00, 6H4-11181-01-00, and Sierra part number 18-3830.

• Precision-cut design ensures proper compression sealing
• Compatible with Yamaha 2-stroke 40HP and 50HP models from 1984-1994
• Direct fit replacement for multiple OEM part numbers

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 Yamaha owners, here's a guide to help you identify your engine's serial/model: Yamaha Serial Number Guide. You can also review exploded diagrams to verify part numbers: Yamaha Parts Diagrams & Catalog.

Technical Specifications

Package Contents

This package includes the following component:

• 1 × Outboard Cylinder Head Gasket

Installation Guide

1. Preparation: Disconnect the battery and allow the engine to cool completely. Gather necessary tools including a torque wrench, gasket scraper, and cleaning solvent.
2. Remove Cylinder Head: Disconnect fuel lines, spark plug wires, and coolant hoses from the cylinder head. Remove the cylinder head bolts in a crisscross pattern, working from outside toward the center.
3. Clean Surfaces: Carefully remove the old gasket material from both the cylinder head and engine block using a gasket scraper. Ensure all surfaces are completely clean and free of debris or oil residue.
4. Inspect Components: Check the cylinder head and block for warping, cracks, or damage. Replace any damaged components before proceeding.
5. Position New Gasket: Place the new cylinder head gasket onto the engine block, ensuring all bolt holes and coolant passages align correctly. Do not apply any sealant unless specified by the manufacturer.
6. Install Cylinder Head: Carefully lower the cylinder head onto the gasket, ensuring proper alignment. Hand-thread all bolts before tightening.
7. Torque Bolts: Tighten the cylinder head bolts in a crisscross pattern, working from the center outward. Follow the manufacturer's torque specifications and sequence for your specific engine model.
8. Reconnect Components: Reattach all fuel lines, spark plug wires, and coolant hoses. Double-check all connections for security.
9. Refill Fluids: Add fresh coolant to the system and check oil levels. Bleed air from the cooling system according to your engine's service manual.
10. Test Engine: Reconnect the battery and start the engine. Check for leaks around the cylinder head gasket while the engine warms up.
11. Re-torque: After the first few hours of operation, re-check and re-torque the cylinder head bolts to specification. This ensures proper seating of the gasket.

Troubleshooting & FAQ

Q: How do I confirm this gasket fits my Yamaha engine?
A: Verify your engine is a Yamaha 40HP or 50HP (including Pro 50) 2-stroke model manufactured between 1984 and 1994. Cross-reference your original part number (6H4-11181-00 or equivalents listed above) with our compatibility table.

Q: What are the signs that my cylinder head gasket needs replacement?
A: Common symptoms include loss of compression, overheating, coolant leaks around the cylinder head, white smoke from the exhaust, rough idle, and coolant mixing with engine oil.

Q: Can I reuse the old cylinder head bolts during installation?
A: It's recommended to replace cylinder head bolts, especially if they are torque-to-yield (TTY) type. Consult your engine's service manual to determine if bolt replacement is required for proper clamping force.

Q: Do I need to use sealant with this gasket?
A: Most cylinder head gaskets are designed to be installed dry without additional sealant. Consult your Yamaha service manual for specific instructions regarding your engine model.

Q: How often should I replace the cylinder head gasket?
A: Cylinder head gaskets should be replaced only when symptoms of failure appear or during major engine rebuilds. With proper maintenance and cooling system care, a quality gasket can last for many years.

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