27-8637251 Closed Center-Riser Elbow Gasket for MerCruiser V6/V8
27-8637251 Closed Center-Riser Elbow Gasket for MerCruiser V6/V8 is backordered and will ship as soon as it is back in stock.
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27-8637251 Closed Center-Riser Elbow Gasket for MerCruiser V6/V8
27-8637251 Closed Center-Riser Elbow Gasket for MerCruiser V6/V8 is backordered and will ship as soon as it is back in stock.
SERDAMARINE / MARINE EXHAUST PARTS
Exhaust Manifold Elbow Riser Gasket — Closed Center-Riser Configuration
This aftermarket exhaust manifold elbow/riser gasket (referencing MerCruiser OEM 27-8637251) is designed for specified GM-built MerCruiser V6 and V8 engines, including rear transmission and inboard applications equipped with center-exit exhaust manifolds and the MerCruiser fresh-water / closed cooling system. It is a closed center-riser gasket for the exhaust manifold and elbow/riser joint and must not be substituted for open or restricted water-passage gasket versions.
Configuration & Specifications
| Exhaust Layout | Center-exit exhaust manifold / center riser |
|---|---|
| Water-Passage Flow Configuration | Closed (distinct from open and restricted center-riser versions) |
| Cooling System Requirement | Fresh-water cooling / MerCruiser closed cooling system |
| Joint Compatibility | Wet Joint on specified 1981 & up / 1983 to 0M serial number models; Dry Joint “Alternative” on specified 0M & up V6/V8 small-block models |
Engine Applications
This gasket applies to GM-built MerCruiser V6 and V8 engines—including rear transmission and inboard configurations—equipped with center-exit exhaust manifolds and the MerCruiser closed (fresh-water) cooling system. Match your engine family, cooling system, exhaust joint design, and serial-number range before ordering.
- MerCruiser Model 175–205 (V6, GM 229 / 262 CID) — Years / Serial Numbers: 1983 through 0M serial numbers. Exhaust & Cooling Configuration: Center Riser, Closed / Fresh-Water Cooling, Wet Joint. Fits when specified
- MerCruiser Model 200–320 (V8 Small Block, GM 305 / 350 / 377 CID) — Years / Serial Numbers: 1983 through 0M serial numbers. Exhaust & Cooling Configuration: Center Riser, Closed / Fresh-Water Cooling, Wet Joint. Fits when specified
- MerCruiser Model 330–370 (V8 Big Block, GM 454 / 502 CID) — Years: 1981 & up. Exhaust & Cooling Configuration: Center Riser, Closed / Fresh-Water Cooling, Wet Joint. Fits when specified
- MerCruiser GM V6 / V8 Small Block — Serial Numbers: 0M serial numbers & up. Exhaust & Cooling Configuration: Center Riser, Closed / Fresh-Water Cooling, Dry Joint “Alternative”. Fits when specified
Reference Numbers
The numbers below are provided for part identification and cross-reference only; they do not imply OEM manufacturer identity or unconditional interchangeability across different cooling configurations.
| MerCruiser Stern / Out Drive OEM References | 27-8637251, 8637251, 27-863725, 863725, 27-860231, 860231, 27-41811, 41811, 87918, 87918A1 |
|---|---|
| OMC OEM References | 0502988, 0508715 |
| Aftermarket References | Sierra: 18-0672, 18-0672-9 GLM: 30220 Mallory: 9-61422 Other Reference Numbers: 8503-GB, MC-47-27-41811 |
| Different Flow-Configuration References (Not Interchangeable) | 27-860232 (Open center-riser gasket version) 27-860233 (Restricted center-riser gasket version) |
Water-passage identification note: Reference 27-860231 corresponds to this closed center-riser gasket, whereas 27-860232 is an open version and 27-860233 is a restricted version. Even when the physical mounting footprint is similar, different water-passage configurations are not interchangeable.
Supplied Parts
- Exhaust manifold elbow/riser gasket (closed center-riser configuration)
Service & Installation Notes
General service guidance only. Use the service manual for your exact engine and exhaust configuration.
- Ensure the engine is shut off, completely cool, and secured against accidental starting before servicing any exhaust components.
- Support the exhaust elbow/riser during removal and installation, and clean both the manifold and elbow/riser mating surfaces without nicking or gouging the sealing planes.
- Compare the replacement gasket directly against your closed-cooling joint layout and service manual diagram to confirm that the closed water-passage configuration matches the specific joint location being serviced.
- Tighten fasteners according to the sequence and specifications in your engine service manual, then inspect the joint for exhaust or coolant leaks during initial operation; shut down immediately and inspect if any leakage or abnormal temperature occurs.
The Serdamarine Approach
Exhaust parts need a configuration match. Serdamarine focuses on marine exhaust manifolds and their related service parts. Application details, connection requirements and public reference numbers are presented together to support part selection.
Questions Before Replacement
How does 27-860231 / 27-8637251 differ from 27-860232 and 27-860233?
Reference 27-860231 (listed along with 27-8637251) designates the closed center-riser gasket for fresh-water / closed cooling applications. Reference 27-860232 is the open water-passage version, and 27-860233 is the restricted water-passage version. Because they control water flow differently across the manifold-to-riser joint, these three versions are not interchangeable.
Does this gasket work with both Wet Joint and Dry Joint MerCruiser exhaust systems?
It applies to Wet Joint center-riser closed-cooling setups on Model 175–205 V6 (GM 229/262 CID, 1983–0M serial numbers), Model 200–320 V8 Small Block (GM 305/350/377 CID, 1983–0M serial numbers), and Model 330–370 V8 Big Block (GM 454/502 CID, 1981 & up). For 0M & up GM V6 and V8 Small Block engines, it is only applicable as the specified Dry Joint “Alternative” configuration.
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