The Buckshot Racing #77 Reed Plate Gasket is an OEM replacement gasket for Mercury OEM part number 840484. It's used with the reed plate and intake assembly on select Mercury high-performance 2.5-liter outboards and Mercury SportJet applications with the 5-Petal SportJet Cage or 7-Petal Race Cage.
This gasket fits key Mercury 2.5L performance engines, including 175 HP Pro XS 6-cylinder 2.5L, 200 HP XS 6-cylinder 2.5L, 200XS ROS, 200XS SST, 2.5XS, and 225X EFI Pro Max outboards. It is also used on select SportJet 200 DFI Jet Drive and SportJet 240 EFI Jet Drive powerhead and pump applications.
What the Reed Plate Gasket Does
The reed plate gasket seals the reed plate area of the Mercury intake system. On a two-stroke Mercury outboard, this sealing surface is critical because the crankcase and reed assembly must control air and fuel flow correctly before it enters the cylinders.
A damaged, crushed, reused, or leaking reed plate gasket can create an air leak. That can cause poor idle quality, lean running, hard starting, hesitation, sneezing through the intake, or tuning issues that may look like carburetor, EFI, DFI, reed, or ignition problems.
Why Replacement Matters
Any time the reed plate, reed cages, intake plate, or front-half assembly is removed, the gasket should be replaced. Once compressed, an old gasket may not reseal evenly. Installing a fresh Mercury 27-840484 reed plate gasket replacement helps restore the correct seal and protects the engine from unwanted air leaks.
This is especially important on Mercury performance engines such as the 175 Pro XS, 200XS, 2.5XS, 225X Pro Max, SST-200, and SportJet 200/240, where clean throttle response, stable idle, and correct fuel-air control matter.
Fitment Focus
This gasket is commonly associated with select Mercury 2.5 liter V6 7-petal reed plate applications, including 175 Pro XS 2.5L, 200 HP XS 2.5L, 200XS ROS, 200XS SST, 2.5XS, 225X EFI Pro Max, 200 DFI SportJet, and 240 EFI SportJet models.
Always confirm fitment by your engine serial number, model listing, and reed plate style before ordering. Mercury used different intake and reed plate combinations across model years, horsepower ranges, and SportJet packages.
Installation Tips
Clean both mating surfaces before installing the new gasket. Remove old gasket material, oil, corrosion, and debris without gouging the aluminum. Make sure the gasket lines up with the reed plate openings and bolt holes before tightening the assembly.
Tighten the reed plate or intake assembly evenly so the gasket compresses flat. After assembly, verify linkage, fuel lines, reeds, and any removed hardware before running the engine.
Buckshot Racing #77 Tech Tip
Do not reuse a 7-petal reed plate gasket after the intake has been apart. A fresh gasket is inexpensive protection against air leaks, poor idle, lean running, and hard-to-find tuning problems.
The Buckshot Racing #77 Reed Plate Gasket is a direct OEM-style replacement for Mercury 27-840484, built for the Mercury 2.5L high-performance and SportJet applications that depend on a clean, sealed reed plate assembly.
Contact Mike Hill at +1-714-697-1716 for tech support.