Exhaust Elbow Gasket – Fits MerCruiser V6 & V8 Closed Cooling Systems (Replaces MerCruiser 27-8637251)
Exhaust Elbow Gasket – Fits MerCruiser V6 & V8 Closed Cooling Systems (Replaces MerCruiser 27-8637251) is backordered and will ship as soon as it is back in stock.
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Delivery and Shipping
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Exhaust Elbow Gasket – Fits MerCruiser V6 & V8 Closed Cooling S...
Product Details
This aftermarket Exhaust Elbow Gasket is a crucial component for maintaining a proper seal between the manifold and riser in MerCruiser V6 & V8 stern drive and inboard engines (1983–2002) that use a closed cooling system. It is specifically designed as a blocked-off gasket to prevent water from passing between the manifold and riser, essential for closed cooling configurations.
It serves as a direct replacement for MerCruiser (Quicksilver) 27-8637251, Sierra 18-1970-2 and 18-1976-2, and OSC 8503-GB.
- Installs between the manifold and riser on center rise outlet exhaust manifolds.
- Designed as a blocked-off gasket specifically for closed cooling systems.
- Not suitable for dry joint exhaust systems.
Part Number Matrix
Use this matrix to confirm equivalent references across OEM and aftermarket.
| Brand | Part Number |
|---|---|
| MerCruiser | 27-8637251 |
| Quicksilver | 27-8637251 |
| Sierra | 18-1970-2 |
| Sierra | 18-1976-2 |
| OSC | 8503-GB |
Engine & Model Compatibility
Confirm your engine model/year in the table below.
For MerCruiser V6 and V8 engines from the early 80s to 2002 using center riser manifolds with closed cooling systems. It is not compatible with dry joint exhaust systems.
| Brand | Model | Years | OEM Part No. | Notes |
|---|---|---|---|---|
| MerCruiser | 4.3L | 1983–2002 | 27-8637251 | For closed cooling systems with center riser manifolds (3 or 4 inch riser). |
| MerCruiser | 5.0L | 1983–2002 | 27-8637251 | For closed cooling systems with center riser manifolds (3 or 4 inch riser). |
| MerCruiser | 5.7L | 1983–2002 | 27-8637251 | For closed cooling systems with center riser manifolds (3 or 4 inch riser). |
| MerCruiser | 6.2L | 1983–2002 | 27-8637251 | For closed cooling systems with center riser manifolds (3 or 4 inch riser). |
| MerCruiser | 7.4L | 1983–2002 | 27-8637251 | For closed cooling systems with center riser manifolds (3 or 4 inch riser). |
| MerCruiser | 8.2L | 1983–2002 | 27-8637251 | For closed cooling systems with center riser manifolds (3 or 4 inch riser). |
| MerCruiser | 454 MAG MPI BRAVO (GEN VI) | 1998 | 27-8637251 | Used with GM 454 V-8 engines. |
| MerCruiser | 502 MAG MPI BRAVO (GEN VI) | 1998 | 27-8637251 | Used with GM 502 V-8 engines. |
Technical Specs
- Product Type
- Exhaust Elbow Gasket
- Installation Location
- Between the manifold and riser.
- Cooling System Type
- Blocked gasket for closed cooling systems only.
- Product Dimensions
- 7.13" H x 6.0" W x 1.06" L
- Package Dimensions
- 7.13" H x 6.0" W x 1.06" L
What’s in the Box
- 1 x Exhaust Elbow Gasket (Replaces 27-8637251)
Installation Notes
- Ensure the engine is completely cool and disconnect the battery.
- Drain the cooling system as required to access the exhaust components.
- Carefully unbolt and remove the exhaust riser/elbow from the manifold.
- Remove the old gasket. Thoroughly clean both mating surfaces, ensuring they are free of all old material, debris, and corrosion.
- Position the new gasket correctly on the manifold, aligning it with the bolt holes.
- Re-install the riser/elbow and tighten the bolts to the manufacturer's recommended torque specifications and sequence.
- Reconnect any hoses, refill the cooling system, and reconnect the battery.
- Start the engine and carefully inspect for any water or exhaust leaks around the new gasket.
Troubleshooting & FAQ
How do I know if this is the right gasket for my MerCruiser engine?
This gasket is for MerCruiser V6 & V8 engines (approx. 1983-2002) with closed cooling systems and center-rise exhaust manifolds. It is a "blocked" gasket. If you have an open or "raw water" cooling system, you will need an open-flow gasket instead. Always verify your OEM part number (27-8637251) and system type before ordering.
What are the signs of a failing exhaust elbow gasket?
Common symptoms include visible water leaks around the manifold/riser joint (especially when the engine is running), rust stains originating from the joint, engine overheating, or water intrusion into the cylinders, which can cause catastrophic engine damage.
Can I reuse my old riser bolts?
It is strongly recommended to use new bolts when replacing exhaust gaskets. Old bolts can be corroded, fatigued, or stretched, and may not achieve the correct torque, leading to leaks and component failure.
Do I need to use sealant with this gasket?
Generally, these gaskets are designed to be installed dry. Applying sealant can sometimes cause the gasket to slip out of place during installation. Always follow the specific instructions in your engine's service manual.
What is the difference between this and a dry joint exhaust gasket?
This gasket is for traditional "wet joint" MerCruiser exhaust systems used from 1983-2002. "Dry joint" systems were introduced around 2002 and use a completely different gasket and sealing design. The parts are not interchangeable. Visually inspect your system to confirm which type you have.
OEM vs. Aftermarket?
This listing is an aftermarket replacement (not OEM). Built to OEM-level specifications with comparable materials. Manufactured in an ISO 9002 facility, batch-inspected for consistency.
Shipping speed & cost?
We ship worldwide quickly—typical transit 5–15 days. Standard shipping is free; expedited options appear at checkout where available.
Warranty & returns?
Covered by a 1-year warranty against manufacturing defects under normal use. If issues arise, contact support with your order details. Returns are accepted within our standard window (unused & in original condition). See our policy page or reach out for instructions.
Safety & Important Info
- Verify images/specifications vs your original part. If anything differs—even if your model appears compatible—do not purchase.
- This is an aftermarket replacement, not an OEM component.
- Professional installation is recommended for safety and performance.
About Sea Sierra
- Pro-Grade Standards — We supply marine parts engineered to OEM-level tolerances and tested for real-world conditions.
- Fast Global Fulfillment — Free standard delivery to most regions in 5–15 days.
- Manufacturer-Direct Value — Fair pricing without compromising on materials or QC.
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