VST Float Chamber O-Ring for Mercury Outboards – Replaces 65L-14984-00, 25-809086, 809086

Product Details

This VST float chamber O-ring is a single replacement sealing ring for the vapor separator tank fuel system on selected Mercury outboard engines. It is used to seal the VST float chamber or cover interface during fuel-system service and helps prevent fuel leakage when correctly installed.

Use the part-number references and engine conditions below to confirm compatibility before ordering. Engine fitment must be checked against the exact model and serial-number range because the same horsepower rating may use different fuel-system components.

Part Number Matrix

The following manufacturer and aftermarket references are associated with this replacement O-ring.

Engine & Model Compatibility

Catalog records identify this O-ring in Mercury fuel-management or vapor-separator diagrams for the following engine applications. Confirm the complete model designation and serial-number range before installation.

Technical Specs

Part Type

VST float chamber O-ring

Application

Vapor separator tank fuel-system sealing

Product Format

Single replacement O-ring

Primary Reference

65L-14984-00

Additional References

809086, 25-809086, and Sierra 18-0715

What's in the Box

• 1 x VST float chamber O-ring

Installation Notes

1. Disconnect the battery and relieve fuel-system pressure before beginning work.
2. Remove the VST cover according to the engine service manual, loosening fasteners evenly and in the specified sequence.
3. Remove the old O-ring from the float-chamber sealing groove without scratching the mating surfaces.
4. Clean the groove and both sealing surfaces with a suitable lint-free cloth. Remove fuel residue, dirt, and fragments of the old seal.
5. Inspect the cover, groove, and mating surfaces for damage or corrosion before installing the replacement.
6. Lightly lubricate the O-ring only as specified by the engine service manual. Do not apply unapproved gasket sealant.
7. Seat the new O-ring evenly in the groove, making sure it is not twisted, pinched, or displaced.
8. Reinstall the VST cover and tighten the fasteners to the manufacturer's specified torque and sequence.
9. Reconnect the battery, pressurize the fuel system, and inspect carefully for leaks before starting the engine.

Troubleshooting & FAQ

How do I know if the VST O-ring needs replacement?

Fuel odor, visible fuel seepage around the VST cover, or a disturbed seal after VST service can indicate that the O-ring should be replaced. Install a new O-ring whenever the cover is removed if required by the service procedure.

Will this fit my Mercury 200HP outboard?

Catalog applications include specific Mercury 200HP EFI and DFI models, but fitment depends on the exact model and serial-number range. Compare your engine identification and existing part reference with the compatibility table before ordering.

Can I reuse the old O-ring if it looks okay?

Reuse is not recommended. An O-ring can flatten, harden, or take a permanent set even when visible damage is not obvious. Replacing it during VST service helps restore the intended seal.

Is this a complete VST repair kit?

No. This listing is for one replacement VST float chamber O-ring only. It does not include a float, needle valve, cover, screws, or other fuel-system components.

Do I need to apply sealant?

Do not use additional sealant unless the engine service manual specifically calls for it. Follow the manufacturer's instructions for cleaning and lubrication during installation.

What should I do after installation?

Pressurize the fuel system and check the VST sealing area for leaks before starting the engine. If leakage continues, stop the engine and inspect the O-ring seating, sealing surfaces, cover, and fastener torque.

Safety & Important Info

• Fuel is flammable. Work in a well-ventilated area away from heat, sparks, and open flames.
• Relieve fuel pressure and disconnect the battery before servicing the VST.
• Verify the exact engine model and serial-number range before purchase; horsepower alone is not sufficient to confirm fitment.
• This is an aftermarket replacement O-ring, not an OEM-branded component.
• Professional installation is recommended for fuel-system service.