Exhaust Manifold Gasket – Fits MerCruiser 120/140 HP 2.5L/3.0L 4-Cylinder Engines

Exhaust Manifold Gasket – Fits MerCruiser 120/140 HP 2.5L/3.0L 4-Cylinder Engines (Replaces 27-96429, 18-1204)

This exhaust manifold gasket is designed for MerCruiser, Volvo Penta, and OMC 2.5L and 3.0L (153/181 CID) 4-cylinder marine engines from approximately 1982 to 1995. It also fits a wide range of General Motors 153 and 181 cubic inch 4-cylinder marine engines used in various stern drive applications.

This part is a direct replacement for MerCruiser 27-96429, Sierra 18-1204 / 18-1204-1, GLM 33570, Mallory 9-61419, OMC 0912164, and Aqua Power 413.

• Mounts between the exhaust manifold and the cylinder head to prevent leaks.
• Constructed from a marine-grade gasket compound with metal reinforcement for durability.
• Engineered to withstand high exhaust temperatures and pressures in the marine environment.

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.

Technical Specifications

Package Contents

• 1 x Exhaust Manifold Gasket (Replaces 27-96429 / 18-1204)

Installation Guide

1. Ensure the engine is completely cool before starting. Disconnect the boat's battery.
2. Drain the engine coolant to a level below the exhaust manifold to prevent spills.
3. Carefully disconnect any hoses or sensors connected to the exhaust manifold.
4. Unbolt and remove the exhaust manifold from the cylinder head. Keep track of bolt order if they differ in length.
5. Thoroughly clean both the cylinder head and manifold mating surfaces. Remove all traces of old gasket material and debris for a clean seal.
6. Position the new gasket, ensuring it aligns correctly with the exhaust ports and bolt holes.
7. Reinstall the exhaust manifold. Hand-tighten the bolts first, then torque them to the manufacturer's specifications in the correct sequence.
8. Reconnect any hoses and sensors that were removed.
9. Refill the cooling system with the appropriate coolant.
10. Reconnect the battery, start the engine, and carefully check for any exhaust or coolant leaks around the gasket.

Troubleshooting & FAQ

Q: How do I know if this gasket fits my MerCruiser 3.0L engine?

A: This gasket is designed for MerCruiser 3.0L models from approximately 1990-1995. It is not compatible with the 3.0LX models (circa 1990 and newer), which require a different gasket (OEM part number 27-815528). Always verify your specific engine model and part number before ordering.

Q: What are the signs of a failing exhaust manifold gasket?

A: Common symptoms of a bad gasket include visible water leaks from the joint between the manifold and cylinder head, water contamination in the engine oil (giving it a milky appearance), reduced engine performance, or an unusual hissing sound from the engine compartment.

Q: Do I need to use sealant with this gasket?

A: No, this gasket is designed to be installed dry. Its reinforced compound material creates a secure seal when the manifold is torqued to the correct specifications. Applying sealant can interfere with this process and is not recommended.

Q: OEM vs. 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.