Mercury – Quicksilver Thermostat O-Ring Gasket | For MerCruiser 4.5L & 6.2L Engines | 806871Q

Overview

A proper seal around your thermostat means steady cooling and reliable performance. The Mercury Marine 806871Q Quicksilver Thermostat O-Ring Gasket is designed for V6 and V8 MerCruiser sterndrive and inboard engines with the newer 1-piece thermostat housing. It’s also used on 4.5L and 6.2L MPI engines (serial number 2A456613 and up). Made from high-quality, heat-resistant rubber, this O-ring creates a tight seal that holds up to vibration, pressure, and temperature swings season after season.

Key Features

• Purpose: Seals the thermostat housing to prevent leaks and maintain proper cooling system pressure.
• Fit: Designed for 1-piece thermostat housings found on newer MerCruiser engines.
• Material: Made from durable, heat- and vibration-resistant rubber for long life.
• Compatibility: Perfect fit for 4.5L and 6.2L MPI MerCruiser engines.
• OEM Quality: Meets Mercury Marine’s original equipment standards for fit and function.

Engine & Boat Compatibility

• V6 and V8 MerCruiser sterndrive and inboard engines made by General Motors
• MerCruiser 4.5L MPI (Multi-Port Injection)
• MerCruiser 6.2L MPI (serial number 2A456613 and newer)

Performance & Real-World Benefits

The 806871Q O-ring gasket may be a small part, but it plays a big role in keeping your engine running cool. A worn or flattened seal can lead to coolant leaks, air pockets, or temperature fluctuations — all of which can cause overheating or reduced performance.

This gasket’s flexible rubber compound maintains its shape and seal under heat and vibration, preventing coolant loss and keeping your thermostat operating properly. Once installed, it ensures a tight, leak-free connection so your engine maintains consistent temperature control in every condition.

Why Choose Mercury OEM

The Quicksilver 806871Q is a genuine Mercury Marine gasket, designed and tested for the engines it serves. Aftermarket gaskets may look similar, but their materials can break down faster or fail to seal evenly, especially under marine temperatures and vibration.

Mercury OEM gaskets are built to perform under pressure — literally. They deliver a perfect fit, long service life, and the kind of reliability that keeps your cooling system maintenance-free and worry-free.

FAQ

Q1: What engines is this gasket made for?
It’s for V6 and V8 MerCruiser engines with 1-piece thermostat housings, including 4.5L and 6.2L MPI models (2A456613 and newer).

Q2: What does it do?
It seals the thermostat housing, keeping coolant contained and ensuring steady engine temperatures.

Q3: How often should I replace it?
Replace it anytime you remove the thermostat housing or notice coolant seepage.

Q4: What’s it made from?
It’s a marine-grade rubber O-ring that resists heat, pressure, and vibration.

Q5: Why OEM instead of aftermarket?
Mercury OEM gaskets are engineered for exact fit and durability, ensuring reliable performance where it counts.