The Mercury OEM VST Gasket 883252 seals the vapor separator tank assembly used on many Mercury and Mariner EFI and DFI fuel systems. The VST, or Vapor Separator Tank, is one of the most important parts of the fuel delivery system because it supplies a controlled reservoir of fuel to the high-pressure fuel pump.
On EFI, DFI, Pro Max, XS, and SportJet applications, a clean and properly sealed VST helps maintain steady fuel delivery, stable idle quality, crisp throttle response, and reliable high-RPM operation.
This gasket is commonly used on Mercury 135 HP, 150 HP, 175 HP, and 200 HP V6 2.5L outboards, including many EFI and DFI models. It also fits performance applications such as the 200XS, 200 HP XS, 225X EFI Pro Max, and related 2.5L Mercury Racing engines.
In larger displacement applications, the same 27 883252 VST gasket is used on many 200 HP, 225 HP, and 250 HP 3.0L EFI engines, including 3.0L SeaPro, 3.0L Marathon, and high-output recreational Mercury V6 models. It is also commonly found in SportJet 240 EFI jet drive powerhead and pump-related fuel system applications.
What the VST Does
The Vapor Separator Tank is designed to separate vapor from liquid fuel and provide the high-pressure pump with a consistent fuel supply.
Fuel enters the VST from the low-pressure side of the fuel system, passes through internal components such as the float, needle, filter screen, and pump cavity, then exits under pressure toward the fuel rail or injection system.
On a Mercury EFI or DFI outboard, a leaking, damaged, or incorrectly installed VST gasket can create fuel seepage, air intrusion, vapor issues, poor fuel pressure stability, and unsafe fuel leakage inside the cowling.
Because the VST is mounted near electrical components, ignition parts, and hot engine surfaces, any sign of fuel leakage should be repaired immediately.
When to Replace the VST Gasket
The 27883252 gasket should be replaced any time the VST cover is removed for service. This includes fuel pump replacement, float inspection, needle and seat service, filter screen cleaning, fuel contamination repair, ethanol-related varnish cleanup, or complete EFI/DFI fuel system maintenance.
Older gaskets often flatten, harden, tear, or stick to the VST body during disassembly. Reusing a compressed gasket can lead to leaks once the system is pressurized. For Mercury 2.5L V6 EFI, 2.5L DFI, 200XS, 225X, 3.0L EFI, and SportJet 240 engines, replacing the gasket during service is inexpensive protection against repeat labor and fuel leakage.
Common Fuel System Symptoms
A failed VST gasket is not always the first cause of poor running, but it should be inspected whenever fuel system problems appear.
Common symptoms can include fuel odor under the cowling, visible fuel staining around the VST cover, hard starting after sitting, poor hot restart behavior, unstable idle, hesitation on acceleration, or loss of power under load.
On performance engines such as the Mercury 200XS, 200 HP XS, 225X Pro Max, and 250 HP EFI 3.0L, fuel delivery problems can become more noticeable at higher RPM because demand increases quickly. A properly sealed VST helps the high-pressure pump maintain consistent supply during acceleration and sustained wide-open throttle operation.
Installation and Service Tips
Before opening the VST, disconnect the battery and relieve fuel system pressure according to the Mercury service manual. Work in a well-ventilated area and keep all ignition sources away from the engine.
Once the VST cover is removed, clean the gasket surfaces carefully without gouging the aluminum housing. Avoid using silicone sealer or excess chemical sealants unless specifically called for by the factory procedure, because loose sealant can contaminate the fuel system and damage injectors.
Inspect the VST cover for warping, corrosion, and pitting around the sealing surface. Check the float, needle, filter screen, pump inlet, and internal passages while the tank is open. If the engine has sat with ethanol fuel, look closely for varnish, debris, swollen rubber parts, or contamination that could restrict fuel flow.
When reassembling, align the Mercury 27-883252 VST gasket correctly, tighten fasteners evenly, and verify there are no fuel leaks after priming and running the engine.
Fitment and Engine Coverage
The Mercury 27-883252 VST gasket is used across a wide range of later (3rd generation VST) Mercury and Mariner outboard and SportJet fuel systems. Typical fitment includes 135 HP V6 2.5L, 150 HP V6 2.5L, 150 Pro XS, 175 HP V6 2.5L, 175 Pro XS, 200 HP V6 2.5L, 200 HP XS, 200XS ROS, 200XS SST, 225X EFI Pro Max, and many 200/225/250 HP 3.0L EFI outboards. It is also found on SportJet 240 EFI, including related powerhead and pump configurations.
Because Mercury used similar VST assemblies across multiple years and engine families, always verify fitment by serial number before ordering, especially on engines that have been repowered, modified, or converted with mixed EFI components.
Buckshot Racing #77 Tech Tip
When servicing a Mercury VST, do not treat the gasket as the only service item. The real value comes from inspecting the entire vapor separator system while it is open.
A new gasket helps seal the housing, but clogged screens, weak pumps, sticking floats, debris in the tank, or restricted passages can still cause fuel pressure problems.
For Mercury EFI, DFI, Pro Max, XS, 3.0L, and SportJet engines, clean fuel and stable pressure are critical. Replacing the Mercury OEM 27-883252 VST gasket during fuel system service helps restore a safe seal, prevents fuel leakage, and supports reliable performance on the water.