27-8637251 Closed Riser Gasket Set (2 Pcs) for MerCruiser V6 & V8

SERDAMARINE / MARINE EXHAUST PARTS

Exhaust Manifold Elbow Riser Gasket Set (2 Pieces) — Closed / Block-Off Cooling Configuration

This two-piece exhaust manifold-to-elbow/riser gasket set (referencing MerCruiser 27-8637251) is designed for specified MerCruiser GM V6 and V8 stern drive and inboard engines with center-riser exhaust manifolds and closed (fresh water) cooling systems. It applies to wet-joint center-riser arrangements from 1981 or 1983 depending on engine family, as well as GM V6 and V8 Small Block Dry Joint "Alternative" systems (0M serial numbers and up); it is not the open-flow or restricted-flow gasket version.

Configuration & Specifications

Engine Applications

Applies to MerCruiser GM-based V6 and V8 stern drive (rear transmission) and inboard engines equipped with center-exit exhaust manifolds and the MerCruiser closed (fresh water) cooling system. Match the engine family, serial number range, cooling-system gasket position, and whether the installed exhaust is a conventional wet-joint center-riser or a Dry Joint "Alternative" system before ordering.

• MerCruiser Model 175–205 (GM V6, 229 / 262 CID) — Years: 1983 to 0M serial numbers. Exhaust configuration: Center Riser, Wet Joint. Cooling configuration: Closed (Fresh Water Cooling). Fits when specified
• MerCruiser Model 200–320 (GM V8 Small Block, 305 / 350 / 377 CID) — Years: 1983 to 0M serial numbers. Exhaust configuration: Center Riser, Wet Joint. Cooling configuration: Closed (Fresh Water Cooling). Fits when specified
• MerCruiser Model 330–370 (GM V8 Big Block, 454 / 502 CID) — Years: 1981 and up. Exhaust configuration: Center Riser, Wet Joint. Cooling configuration: Closed (Fresh Water Cooling). Fits when specified
• MerCruiser GM V6 / V8 Small Block — Dry Joint "Alternative" System — Serial numbers: 0M and up. Exhaust configuration: Center Riser, Dry Joint "Alternative" replacement system using the specified fresh-water-cooling closed gasket position. Fits when specified

Additional model-specific applications

• MerCruiser MODEL 175-205 — GM V6, 229 CID, Wet Joint, Center Riser, Closed / Fresh Water Cooling; Year / serial number condition “1983 - 0M SN#’s.”
• MerCruiser MODEL 175-205 — GM V6, 262 CID, Wet Joint, Center Riser, Closed / Fresh Water Cooling; Year / serial number condition “1983 - 0M SN#’s.”
• MerCruiser MODEL 200-320 — GM V8 Small Block, 305 CID, Wet Joint, Center Riser, Closed / Fresh Water Cooling; Year / serial number condition “1983 - 0M SN#’s.”
• MerCruiser MODEL 200-320 — GM V8 Small Block, 350 CID, Wet Joint, Center Riser, Closed / Fresh Water Cooling; Year / serial number condition “1983 - 0M SN#’s.”
• MerCruiser MODEL 200-320 — GM V8 Small Block, 377 CID, Wet Joint, Center Riser, Closed / Fresh Water Cooling; Year / serial number condition “1983 - 0M SN#’s.”
• MerCruiser MODEL 330-370 — GM V8 Big Block, 454 CID, Wet Joint, Center Riser, Closed / Fresh Water Cooling; from 1981 onward,
• MerCruiser MODEL 330-370 — GM V8 Big Block, 502 CID, Wet Joint, Center Riser, Closed / Fresh Water Cooling; from 1981 onward,
• MerCruiser GM V6 — Dry Joint “Alternative”, Fresh Water Cooling gasket position; serial condition “0M SN#’s & UP.”
• MerCruiser GM V8 Small Block — Dry Joint “Alternative”, Fresh Water Cooling gasket position; serial condition “0M SN#’s & UP.”
• MerCruiser GM-manufactured V6 inboard engines with center-exit exhaust manifolds and MerCruiser closed cooling.
• MerCruiser GM-manufactured V8 inboard engines with center-exit exhaust manifolds and MerCruiser closed cooling.
• MerCruiser GM-manufactured V6, application described as “rear transmissions,” with center-exit exhaust manifolds and MerCruiser closed cooling.
• MerCruiser GM-manufactured V8, application described as “rear transmissions,” with center-exit exhaust manifolds and MerCruiser closed cooling.

Reference Numbers

The numbers below are provided for part identification and cross-reference only; they do not imply manufacturer identity or guaranteed interchangeability across different cooling configurations.

Supplied Parts

• 2 × Exhaust Manifold Elbow / Riser Gasket (Closed / Fresh Water Cooling configuration)

Service & Installation Notes

General service guidance only. Use the service manual for your exact engine and exhaust configuration.

1. Shut off the engine, allow the exhaust system to cool completely, and disconnect the battery or disable ignition to prevent accidental starting.
2. Drain the cooling passages in the exhaust manifold and elbow/riser according to the engine service manual before loosening joint fasteners, and support heavy exhaust components during removal.
3. Remove all old gasket material and inspect both the manifold and elbow/riser mating surfaces for flatness, corrosion, or pitting while protecting the sealing surfaces from gouges.
4. Verify that the closed (block-off) gasket matches the required cooling circuit position for your closed-cooling system before reassembling and tightening fasteners to the factory specification.
5. After installation, run the engine with proper cooling water supply and inspect the manifold-to-riser joint for coolant, water, or exhaust leaks; stop the engine 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