Exhaust Manifold Gasket for MerCruiser GM V8 454/502 Engines – Replaces 27-46820
Exhaust Manifold Gasket for MerCruiser GM V8 454/502 Engines – Replaces 27-46820 is backordered and will ship as soon as it is back in stock.
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Exhaust Manifold Gasket for MerCruiser GM V8 454/502 Engines – Repl...
Exhaust Manifold Gasket for MerCruiser GM V8 454/502 Engines – Replaces 27-46820 is backordered and will ship as soon as it is back in stock.
Product Details
This aftermarket exhaust manifold gasket is designed for selected MerCruiser V8 big-block applications using GM 454 and 502 CID engines. It seals the exhaust-manifold connection to help prevent exhaust and cooling-system leaks when the correct manifold, riser, and gasket configuration are used.
The gasket is listed for MerCruiser applications associated with 7.4L 454, 8.1L 496, and 8.2L 502 GM-based engines. The applicable engine and exhaust configuration must be confirmed before installation because wet-joint, dry-joint, manifold, riser, and elbow gaskets are not interchangeable solely by engine displacement.
- Replacement exhaust manifold gasket for selected MerCruiser GM V8 applications.
- Used at the manifold-to-cylinder-head or adapter/manifold sealing interface, depending on the engine exhaust configuration.
- Suitable for specific 454 CID, 7.4L, 496/8.1L, and 502/8.2L applications listed below.
- Aftermarket replacement part; not manufactured by Mercury Marine, Volvo Penta, OMC, Crusader, Sierra, or GLM.
Part Number Matrix
Use the following manufacturer and aftermarket references to compare your existing gasket. These references identify related replacement applications and do not by themselves confirm every engine fitment.
| Brand | Reference Number | Reference Type |
|---|---|---|
| Mercury Marine / MerCruiser | 27-46820 | OEM reference |
| Mercury Marine / MerCruiser | 27-46820A1 | OEM reference |
| OMC Cobra | 0508878 | OEM reference |
| OMC Cobra | 0778127 | OEM reference |
| OMC Cobra | 0909613 | OEM reference |
| OMC Cobra | 3852472 | OEM reference |
| Volvo Penta | 3852472 | OEM reference |
| Crusader | 96653 | OEM reference |
| Sierra | 18-0418 | Aftermarket reference |
| GLM | 33760 | Aftermarket reference |
Engine & Model Compatibility
The company fitment information identifies this gasket for selected MerCruiser wet-joint exhaust-manifold applications covering GM 454/502 CID V8 engines, models 330–370, from 1981 and later. Related company application notes also identify GM-based 7.4L, 8.1L, and 8.2L V8 engines.
| Brand | Engine / Application | Displacement | Year Guidance | Important Note |
|---|---|---|---|---|
| MerCruiser | Selected V8 big-block applications, models 330–370 | GM 454/502 CID | 1981 and later | Company-listed wet-joint application; verify manifold and riser configuration. |
| MerCruiser | GM-based V8 applications | 7.4L 454, 8.1L 496, 8.2L 502 | Verify by engine and serial number | Do not use displacement alone to select the gasket. |
For an exact match, compare the gasket shape, bolt-hole pattern, exhaust-port openings, manifold or riser design, and engine serial number. The related gasket references 27-863724, 27-860231, and 27-863726 are different component applications and should not be treated as interchangeable with this manifold gasket without confirming the complete exhaust assembly.
Technical Specs
- Product Type
- Exhaust manifold gasket
- Application
- Selected MerCruiser GM V8 big-block exhaust systems
- Engine Coverage
- GM 454/502 CID; related 7.4L, 8.1L, and 8.2L applications as listed
- Exhaust Configuration
- Primarily company-listed wet-joint applications; verify the exact configuration before ordering
- Installation Location
- Exhaust manifold sealing interface
- Quantity per Package
- 1 gasket
- Construction
- Aftermarket gasket construction; exact material composition is not specified
- OEM Reference
- Mercury Marine / MerCruiser 27-46820 and 27-46820A1
What’s in the Box
- 1 x aftermarket exhaust manifold gasket
Installation Notes
- Allow the engine and exhaust components to cool completely before starting work.
- Disconnect the battery and follow the engine manufacturer's safety procedures.
- Remove the exhaust manifold as directed by the applicable service manual.
- Clean the cylinder-head and manifold mating surfaces thoroughly. Remove old gasket material, carbon, rust, and sealant without damaging the sealing surfaces.
- Compare the new gasket with the removed gasket and confirm the ports and bolt holes align before installation.
- Install the gasket in the correct orientation. Do not substitute a manifold, riser, elbow, or end-cap gasket for this part.
- Reinstall the manifold and tighten the fasteners in the manufacturer's specified sequence and to the specified torque.
- Reconnect hoses, sensors, and the battery, then run the engine and check carefully for exhaust, water, or coolant leaks.
Troubleshooting & FAQ
How do I confirm that this gasket fits my engine?
Match your existing OEM or aftermarket reference to the Part Number Matrix, then confirm the engine model, serial number, manifold design, riser arrangement, gasket outline, and port locations. If any of these differ, confirm the application before purchasing.
Is this the same as a riser or exhaust elbow gasket?
No. Manifold, riser, elbow, adapter-plate, end-cap, and block-off gaskets serve different sealing locations. Related reference numbers may appear in the same exhaust system but should not be substituted without application-specific confirmation.
What are common signs of a failed exhaust manifold gasket?
Possible symptoms include ticking or tapping noises, visible soot or black marks near the manifold joint, exhaust odor, water or coolant leakage, and reduced engine performance. Inspect the complete exhaust assembly before replacing the gasket.
Can I reuse the old gasket?
No. Exhaust gaskets should normally be replaced whenever the manifold is removed. Reusing a compressed or damaged gasket can lead to exhaust or cooling-system leaks.
Is this an OEM part?
No. This is an aftermarket replacement gasket made for applications associated with the listed OEM references. Brand names and OEM numbers are used only to identify application compatibility.
What if my engine appears in a related catalog but the gasket looks different?
Do not rely on the engine name or displacement alone. Stop and compare the gasket profile, ports, bolt holes, manifold, riser, and serial-number range. A different physical design indicates that the application needs further confirmation.
Safety & Important Info
- Verify the OEM or aftermarket reference, gasket shape, exhaust configuration, engine model, and serial number before ordering.
- This listing is for one exhaust manifold gasket, not a complete manifold, riser, elbow, or full exhaust repair kit.
- Do not use related gasket numbers as automatic substitutes; they may belong to different sealing locations.
- Use the applicable service manual for removal procedures, bolt sequence, torque specifications, and pressure or leak testing.
- Professional installation is recommended when access is restricted or the manifold and cooling system require extensive disassembly.
About Sea Sierra
- Marine Parts Focus — We supply replacement components for common marine propulsion and exhaust-system applications.
- Application-Conscious Support — Matching the engine, serial number, component location, and reference number helps avoid incorrect substitutions.
- Aftermarket Value — Practical replacement parts for routine marine maintenance and repair.
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