27-99777-2 Open Rear-Riser Exhaust Elbow Gasket for MerCruiser

SERDAMARINE / MARINE EXHAUST PARTS

Exhaust Manifold-to-Elbow Gasket — Rear Riser, Open Type

This aftermarket open-type gasket seals the joint between the exhaust manifold and the exhaust elbow or adaptor on rear-riser MerCruiser Stern / Out Drive installations referenced under 27-99777-2, including specified 4/6-cylinder (1968–1982, except 120 hp), V8 (1978–1982), Model 120/140 inline-4, and 2.5L / 3.0L / 3.0LX series engines.

It is the open rear-riser configuration and differs from the closed-cooling gasket version referenced as MerCruiser 27-92720 or GLM 32630.

Configuration & Specifications

Engine Applications

Select this gasket by matching both the engine application and the open rear-riser manifold-to-elbow or adaptor joint configuration rather than relying on engine displacement alone.

• MerCruiser 4/6-Cyl. (except 120 hp) — Years: 1968–1982. Position and configuration: Rear riser, open-type gasket at the exhaust manifold to elbow or adaptor joint. Fits when specified
• MerCruiser All V8 — Years: 1978–1982. Position and configuration: Rear riser, open-type gasket at the exhaust manifold to elbow or adaptor joint. Fits when specified
• MerCruiser MODEL 140 — INLINE 4, GM 181 CID, 4-CYL. — Years: 1968–1982. Position and configuration: Rear riser, open-type gasket at the exhaust manifold to elbow or adaptor joint. Fits when specified
• MerCruiser MODEL 120/140 — INLINE 4, 153/181 CID, 4-CYL. — Years: 1982–1995. Position and configuration: Rear riser, open-type gasket at the exhaust manifold to elbow or adaptor joint. For a 1982 Model 120, verify the actual manifold/elbow version and required gasket number, as 1968–1982 120 hp applications are excluded. Fits when specified
• MerCruiser 2.5L — Years: 1983–1994. Position and configuration: Rear riser, open-type gasket at the exhaust manifold to elbow or adaptor joint. Fits when specified
• MerCruiser 3.0L — Years: 1983–1994. Position and configuration: Rear riser, open-type gasket at the exhaust manifold to elbow or adaptor joint. Fits when specified
• MerCruiser MODEL 3.0LX / 3.0L — INLINE 4, GM 181 CID, 4-CYL. — Years: 1990 & up. Position and configuration: Rear riser, open-type gasket at the exhaust manifold to elbow or adaptor joint. Verify the installed exhaust-joint version on 1990-onward engines, as the model name alone does not identify later design changes. Fits when specified

Not Suitable For

• MerCruiser 4-Cyl. 120 hp (1968–1982) — Excluded from the 1968–1982 4/6-cylinder application range; for a 1982 Model 120 transition year, check the installed manifold/elbow version and part number. Not suitable
• Closed-Cooling Joint Applications Calling for MerCruiser 27-92720 or GLM 32630 — Requires the closed-cooling gasket configuration rather than this open-type rear-riser gasket. Not suitable

Additional model-specific applications

• MerCruiser 4-cylinder engines, 1968–1982; rear-riser open manifold-to-elbow/adaptor gasket application, excluding 120 HP engines.
• MerCruiser 6-cylinder engines, 1968–1982; rear-riser open manifold-to-elbow/adaptor gasket application, excluding 120 HP engines.
• MerCruiser All V8 engines, 1978–1982; rear-riser open manifold-to-elbow/adaptor gasket. Individual models and horsepower are not specified.

Reference Numbers

The numbers below are provided for part identification and cross-reference only; they do not indicate that this aftermarket part was manufactured by the referenced brands, and numbers for other joint configurations are separated below.

Supplied Parts

• 4 × Exhaust manifold-to-elbow gasket (rear riser, open type)

Service & Installation Notes

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

1. Shut off the engine, allow all exhaust components to cool completely, and disconnect the battery to prevent accidental cranking before loosening the elbow or adaptor hardware.
2. Support the exhaust elbow or adaptor during removal and installation so its weight does not damage the manifold sealing surfaces or threads.
3. Clean old gasket material from both the manifold and the elbow or adaptor mating faces while protecting the machined surfaces from gouges, and verify that the passage layout matches the open rear-riser gasket.
4. Align the new gasket with all bolt holes and passages, then tighten the fasteners to the sequence and specification listed in your engine service manual; stop operation immediately and inspect the joint if any exhaust or water leak is detected during initial run-up.

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