Exhaust Manifold Gasket for MerCruiser 120/140 HP 2.5L/3.0L 4-Cylinder Engines – Replaces 27-96429, 18-1204
Exhaust Manifold Gasket for MerCruiser 120/140 HP 2.5L/3.0L 4-Cylinder Engines – Replaces 27-96429, 18-1204 is backordered and will ship as soon as it is back in stock.
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Worry-free returns
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Delivery and Shipping
Delivery and Shipping
Orders are typically processed within 1–2 business days.
U.S. orders usually arrive within 6–15 days, depending on stock location and destination.
International delivery times may vary due to customs processing.
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Exhaust Manifold Gasket for MerCruiser 120/140 HP 2.5L/3.0L 4-Cylin...
Exhaust Manifold Gasket for MerCruiser 120/140 HP 2.5L/3.0L 4-Cylinder Engines – Replaces 27-96429, 18-1204 is backordered and will ship as soon as it is back in stock.
Product Details
This high-quality exhaust manifold gasket for MerCruiser 120/140 HP 2.5L and 3.0L 4-cylinder marine engines creates a tight seal between the exhaust manifold and cylinder head. It is designed for applicable MerCruiser, Volvo Penta, and OMC engines using the 27-96429-style manifold gasket, including GM 153 CID (2.5L) and GM 181 CID (3.0L) applications listed below.
This aftermarket replacement is commonly referenced as a replacement for MerCruiser 27-96429, Sierra 18-1204 and 18-1204-1, GLM 33570, Mallory 9-61419, and OMC 0912164. Always compare the original gasket, engine model, and application details before ordering.
- Made from a marine-grade gasket compound with metal reinforcement for durability.
- Designed to withstand high exhaust temperatures and pressure while helping prevent leaks.
- Installs between the exhaust manifold and cylinder head.
Part Number Matrix
Use this matrix to compare equivalent manufacturer and aftermarket references.
| Brand | Part Number |
|---|---|
| MerCruiser | 27-96429 |
| Sierra | 18-1204 |
| Sierra | 18-1204-1 |
| GLM | 33570 |
| Mallory | 9-61419 |
| OMC | 0912164 |
| Aqua Power | 413 |
Engine & Model Compatibility
Confirm the complete engine model, year, and original gasket number before ordering. This gasket is not intended for MerCruiser 3.0LX applications, which use a different gasket design and part reference.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| MerCruiser | 120 | 120 HP | 4-Stroke | 1982–1995 | 27-96429 | GM 153 CID (2.5L), 4-cylinder |
| MerCruiser | 140 | 140 HP | 4-Stroke | 1982–1995 | 27-96429 | GM 181 CID (3.0L), 4-cylinder |
| MerCruiser | 3.0L | 130–135 HP | 4-Stroke | 1990–1995 | 27-96429 | GM 181 CID; verify the exact manifold and gasket pattern |
| MerCruiser | 3.0LX | 135 HP | 4-Stroke | 1990+ | 27-815528 | Not compatible with this gasket |
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| OMC | 3.0L | 140 HP | 4-Stroke | 1973–1990 | 0912164 | GM 181 CID engines |
| Volvo Penta | 3.0L | 130–140 HP | 4-Stroke | 1982–1990 | GM 181 CID engines; verify the original gasket reference |
Technical Specs
- Product Type
- Exhaust manifold gasket
- Installation Location
- Between the exhaust manifold and cylinder head
- Material
- Marine-grade gasket compound with metal reinforcement
- Color
- Gray/metallic
- Compatible Engine Families
- GM 153 CID (2.5L) and GM 181 CID (3.0L) 4-cylinder marine engines where the listed gasket reference applies
- Applications
- Applicable MerCruiser 120/140 HP and selected OMC and Volvo Penta 3.0L applications; not for MerCruiser 3.0LX
- Operating Temperature
- High-temperature rated for exhaust-system service
- Other Attributes
- Designed to withstand exhaust heat and pressure while helping prevent leaks at the cylinder-head-to-manifold joint
What’s in the Box
- 1 x Exhaust manifold gasket
Installation Notes
- Ensure the engine is completely cool and disconnect the battery.
- Drain the engine cooling system as required for the specific engine and manifold arrangement.
- Remove any components obstructing access to the exhaust manifold.
- Carefully unbolt and detach the exhaust manifold from the cylinder head.
- Remove the old gasket. Thoroughly clean and inspect both mating surfaces; they should be flat, dry, and free of debris.
- Position the replacement gasket and verify alignment with all bolt holes and ports.
- Reinstall the exhaust manifold, starting all bolts by hand.
- Tighten the manifold bolts using the manufacturer’s recommended torque specification and sequence.
- Refill the cooling system as required and reconnect the battery.
- Start the engine and carefully check for exhaust or coolant leaks around the manifold.
Troubleshooting & FAQ
How do I know if my exhaust manifold gasket is failing?
Possible signs include an audible exhaust leak or ticking sound, visible water or coolant leakage at the manifold-to-cylinder-head joint, rough engine operation, or evidence of water entering a cylinder. Stop operating the engine and investigate promptly if a serious leak or hydrolock risk is suspected.
Is this gasket compatible with my MerCruiser 3.0LX model?
No. This gasket is intended for the listed earlier 3.0L applications and is not compatible with MerCruiser 3.0LX models. The 3.0LX uses a different gasket reference, commonly identified as OEM part number 27-815528. Verify the engine model and original gasket before ordering.
Should I use sealant or adhesive with this gasket?
This gasket is generally installed dry. Do not apply sealant unless the engine manufacturer’s service information specifically requires it, because sealant can interfere with the seal or contaminate the exhaust and cooling passages.
Is this an OEM gasket?
No. This listing is for an aftermarket replacement gasket intended to replace the listed OEM and aftermarket references. Confirm the original part number and gasket shape before installation.
How much is shipping and how fast is it?
We ship worldwide quickly—typical transit time is 5–15 days. Standard shipping is free to most regions. Expedited shipping options, where available, will be displayed at checkout.
What is the warranty and return policy?
This part is covered by a 1-year warranty against manufacturing defects under normal use. Returns are accepted within the standard return window for unused items in their original condition. Contact support with your order details for assistance.
Safety & Important Info
- Verify the engine model, year, original gasket, port layout, and applicable part number before ordering.
- Do not install this gasket on a MerCruiser 3.0LX application unless the correct gasket reference has been independently confirmed.
- This is an aftermarket replacement part, not an OEM component.
- Professional installation is recommended for safety and reliable performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered for demanding real-world conditions.
- Fast Global Fulfillment — Free standard delivery to most regions, typically arriving in 5–15 days.
- Manufacturer-Direct Value — Fair pricing without compromising on materials or quality control.
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