The Reed Plate Intake Gasket, Mercury 27-841220 is a critical sealing component located between the reed plate assembly and crankcase on Mercury 3.0-liter and 3.2-liter two-stroke outboards.
Whenever reed valves, reed cages, intake components, or the reed plate are removed, replacing this gasket is considered standard practice to ensure proper sealing and maintain crankcase pressure integrity.
This gasket supersedes the earlier Mercury 27-804680 design and utilizes modern AFM (Advanced Fiber Material) gasket technology for improved sealing performance, fuel resistance, and long-term durability.
Why the Reed Plate Gasket Matters
Unlike a four-stroke engine, a two-stroke relies on crankcase pressure pulses to move the air-fuel mixture through the intake system and into the combustion chamber. Any air leak between the reed plate and crankcase can negatively affect idle quality, throttle response, fuel delivery, and overall engine performance.
A properly sealed reed plate helps maintain consistent crankcase pressure and ensures the reeds operate as intended. Whenever reeds or reed cages are replaced, installing a new gasket helps eliminate the risk of vacuum leaks caused by compressed, damaged, or reused gaskets.
Upgraded AFM Gasket Material
The Mercury 27-841220 gasket uses AFM sealing material, a significant improvement over many older composite gaskets.
AFM gaskets are designed to resist fuel exposure, heat cycling, vibration, and long-term compression set, making them particularly well-suited for high-performance and direct-injected outboard applications.
The material maintains sealing integrity under the demanding conditions found in Mercury EFI, Optimax, Pro XS, and Mercury Racing engines while providing excellent durability in both freshwater and saltwater environments.
Designed for Mercury 3.0L & 3.2L Two-Stroke Engines
The 27-841220 gasket fits a wide range of Mercury V6 two-stroke outboards equipped with reed plate intake systems.
Applications include Mercury 200 HP, 225 HP, 250 HP, and 300 HP engines found in EFI, DFI, Optimax, Pro XS, Sport XS, and Mercury Racing configurations. It is also commonly used in 300X and various 3.2-liter stroker performance builds based on the Mercury 3.0-liter platform.
Because Mercury utilized this gasket across numerous production years and model variations, serial-number verification is always recommended when ordering engine components.
Cross-Reference Part Numbers
The Mercury 27-841220 reed plate gasket cross references numerous aftermarket and superseded part numbers, including: 804680, 27-804680, 841220, 850283, 18-2707, 10-2707, 2707, and 516-40-01.
Recommended During Reed Service
Reed valves and reed cages are common maintenance and performance upgrade items on Mercury two-stroke outboards. Whether installing OEM reeds, composite reeds, or complete reed cage assemblies, replacing the reed plate gasket at the same time helps ensure a proper seal and prevents having to repeat the repair later due to an intake air leak.
Considering the labor involved in accessing the reed plate assembly, installing a fresh gasket during reassembly is inexpensive insurance for long-term reliability.
Final Thoughts from Buckshot Racing #77
The Mercury 27-841220 AFM Reed Plate Intake Gasket is a simple but important component that helps maintain proper crankcase sealing and intake efficiency on Mercury 3.0L and 3.2L two-stroke outboards.
Designed as an upgraded replacement for Mercury 27-804680, the AFM material provides improved durability and sealing performance for EFI, Optimax, Pro XS, and Mercury Racing applications.
Whether you're replacing reeds, upgrading reed cages, or rebuilding a Mercury V6 powerhead, a new reed plate gasket is an essential part of a professional-quality repair.