Closed Riser Gasket Set for MerCruiser GM V6 & V8 5.0L–8.2L Engines – Replaces 27-863725 and 27-41811
Closed Riser Gasket Set for MerCruiser GM V6 & V8 5.0L–8.2L Engines – Replaces 27-863725 and 27-41811 is backordered and will ship as soon as it is back in stock.
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Closed Riser Gasket Set for MerCruiser GM V6 & V8 5.0L–8.2L Eng...
Closed Riser Gasket Set for MerCruiser GM V6 & V8 5.0L–8.2L Engines – Replaces 27-863725 and 27-41811 is backordered and will ship as soon as it is back in stock.
Product Details
This closed riser gasket set is designed for MerCruiser stern-drive applications using GM V6 and V8 engines from 5.0L through 8.2L with a fresh-water, closed-cooling system. It is intended for exhaust manifolds and center-rise exhaust outlets used on applicable MerCruiser engines produced from the early 1980s through the 1990s and later applications that use the same gasket configuration.
The set is listed as a replacement for several OEM and aftermarket references, including Mercury MerCruiser 27-863725, 27-41811, 27-860231, Sierra 18-0672, and the additional references shown below. Confirm the gasket shape, bolt-hole pattern, cooling-system configuration, and existing part number before ordering.
- Designed for closed-riser, fresh-water cooling applications.
- Used at the connection between the exhaust manifold and center-rise outlet.
- Includes two gaskets for a complete installation.
- For applicable MerCruiser GM V6 and V8 engine configurations.
Part Number Matrix
Use the following references to compare the gasket with your existing part. Part-number cross-references should be confirmed against the physical gasket and engine configuration before installation.
| Brand | Part Number |
|---|---|
| Mercury MerCruiser | 27-863725 / 27-8637251 |
| Mercury MerCruiser | 27-41811 |
| Mercury MerCruiser | 27-860231 |
| Sierra | 18-0672 |
| Barr | MC-20-87918 / MC-47-27-41811 |
| GLM | 30220 |
| OSCO | 8503-GB |
| Mallory | 9-61422 |
| UANOFCN | 863725 |
Engine and Model Compatibility
The applications below represent the listed MerCruiser compatibility range. Engine model, year, horsepower, and cooling-system configuration must be considered together. Always compare the original gasket before installation.
| Brand | Model | Rated HP | Stroke | Years | OEM Part No. | Notes |
|---|---|---|---|---|---|---|
| MerCruiser | 4.3L | 175–205 | 4-Stroke | 1987–1995 | 27-863725 | V6 |
| MerCruiser | 4.3LX | 175–205 | 4-Stroke | 1987–1995 | 27-863725 | V6 |
| MerCruiser | 4.3L LH | 175–205 | 4-Stroke | 1987–1995 | 27-863725 | V6 |
| MerCruiser | 4.3L LXH | 175–205 | 4-Stroke | 1987–1995 | 27-863725 | V6 |
| MerCruiser | 4.3L EFI | 175–205 | 4-Stroke | 1987–1995 | 27-863725 | V6 |
| MerCruiser | 4.3L MPI | 175–205 | 4-Stroke | 1987–1995 | 27-863725 | V6 |
| MerCruiser | 262 MAG | 175–205 | 4-Stroke | 1987–1995 | 27-863725 | V6, 4.3L |
| MerCruiser | 200 | 200 | 4-Stroke | 1981–1986 | 27-863725 | V8, 305 CID |
| MerCruiser | 228 | 228 | 4-Stroke | 1981–1986 | 27-863725 | V8, 305 CID |
| MerCruiser | 230 | 230 | 4-Stroke | 1981–1986 | 27-863725 | V8, 305 CID |
| MerCruiser | 230 MIE | 230 | 4-Stroke | 1981–1986 | 27-863725 | V8, 305 CID |
| MerCruiser | 260 | 260 | 4-Stroke | 1981–1986 | 27-863725 | V8, 350 CID |
| MerCruiser | 5.0L | 200–260 | 4-Stroke | 1988–1995 | 27-863725 | V8, 305 CID |
| MerCruiser | 5.0LX | 200–260 | 4-Stroke | 1988–1995 | 27-863725 | V8, 305 CID |
| MerCruiser | 898 | 200–260 | 4-Stroke | 1983–1984 | 27-863725 | V8, 305 CID |
| MerCruiser | 5.0L MPI | 200–260 | 4-Stroke | 1988–1995 | 27-863725 | V8, 305 CID |
| MerCruiser | 5.7L | 250–300 | 4-Stroke | 1988–1995 | 27-863725 | V8, 350 CID |
| MerCruiser | 7.4L | 330–340 | 4-Stroke | 1988–1995 | 27-863725 | V8, 454 CID |
| MerCruiser | 8.2L | 380–430 | 4-Stroke | 1988–1995 | 27-863725 | V8, 502 CID |
| MerCruiser | 350 MAG | 300 | 4-Stroke | 1987–1995 | 27-863725 | V8, 350 CID |
Technical Specifications
- Product Type
- Closed-riser exhaust manifold gasket set
- Installation
- For applicable fresh-water, closed-cooling systems
- Connection
- Exhaust manifold to center-rise outlet
- Material
- Marine-grade gasket material
- Application
- Applicable MerCruiser GM V6 and V8 configurations using the listed gasket pattern
What's in the Box
- 2 x Closed riser exhaust manifold gasket, replacing 27-863725 / 27-8637251 references
Installation Notes
- Disconnect the battery and allow the engine to cool completely before beginning work.
- Drain the cooling system as necessary so coolant does not spill excessively when the riser is removed.
- Disconnect any hoses, sensors, or other components attached to the exhaust riser.
- Remove the mounting bolts securing the riser to the manifold. Record the bolt positions and lengths for reassembly.
- Carefully separate the riser from the manifold and account for residual coolant or water.
- Clean the manifold and riser mating surfaces thoroughly. Remove old gasket material, corrosion, and debris without damaging the sealing surfaces.
- Position the new gasket on the manifold, aligning all bolt holes and passages.
- Lower the riser into place and start the bolts by hand to avoid cross-threading.
- Tighten the bolts in the manufacturer's specified sequence and to the specified torque. Do not overtighten.
- Reconnect hoses and sensors, refill the cooling system, and reconnect the battery.
- Run the engine and inspect the joint for exhaust, coolant, or water leaks.
Use the engine manufacturer's service manual for the correct torque values, tightening sequence, sealant requirements, and cooling-system refill procedure.
Troubleshooting and FAQ
How do I confirm that this gasket fits my engine?
Verify that your engine uses the listed fresh-water, closed-cooling configuration, then compare the engine model, year, horsepower, and existing part number with the compatibility table and part-number matrix. Also compare the physical gasket shape and bolt-hole pattern before installation.
What is the difference between a closed-riser gasket and an open gasket?
A closed-riser gasket is intended for the applicable closed-cooling exhaust configuration and does not use the same large raw-water passage arrangement found on some open or raw-water-cooled applications. The gasket must match the specific manifold, riser, and cooling-system design.
What are the signs of a failing riser gasket?
Possible signs include coolant or water leaking at the manifold-to-riser joint, exhaust leakage, steam, abnormal engine temperature, or water contamination in the engine oil. Stop operation and inspect the exhaust and cooling systems if any of these symptoms occur.
How often should riser gaskets be replaced?
Inspect exhaust-manifold and riser joints during routine maintenance and whenever the riser or manifold is removed. Replacement intervals vary with use, storage, coolant condition, and exposure to salt water, so follow the engine manufacturer's service recommendations.
Do I need sealant with this gasket?
Do not apply sealant unless the engine or gasket manufacturer's service instructions specifically require it. Many exhaust gaskets are designed for dry installation, and excess sealant can interfere with proper seating or cooling passages.
Can I reuse the old riser bolts?
Inspect all bolts for corrosion, damaged threads, stretching, or other wear. Replace any questionable fasteners and follow the service manual's requirements for bolt reuse and torque.
Is this an OEM component?
This listing is for an aftermarket replacement gasket set and is not represented as a Mercury MerCruiser OEM component. The listed OEM and aftermarket numbers are provided as reference numbers for comparison.
What are the shipping and return terms?
Standard shipping and return eligibility are determined by the store policies shown at checkout and on the applicable policy pages. Product condition and packaging requirements may apply to returns.
Safety and Important Information
- Verify the engine model, year, cooling-system type, gasket configuration, and existing part number before ordering.
- Do not install this gasket on an application with a different passage layout or bolt-hole pattern.
- Allow the engine to cool and disconnect the battery before service.
- Use the manufacturer's service manual for torque values, tightening sequence, and installation requirements.
- Professional installation is recommended when working on marine exhaust or cooling systems.
About Sea Sierra
- Pro-Grade Standards — We supply marine replacement parts selected for demanding real-world applications.
- Global Fulfillment — Shipping options and estimated delivery times are shown at checkout where available.
- Manufacturer-Direct Value — We aim to provide practical replacement solutions with clear application information.
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