Mercury – Replacement Thermostat | 170 Degree Cooling System | Marine-Grade Steel | 864493

Overview

Out on the water, there’s something reassuring about an engine that finds its temperature, settles in, and just runs the way it’s supposed to. You can feel it in the throttle, hear it in the steady hum behind you, and trust it when the day takes you farther from shore than planned. A dependable thermostat plays a bigger role in that confidence than most folks realize. The Mercury Marine 864493 Thermostat helps your engine warm up quickly, stay balanced, and deliver smooth, predictable performance every time you power up.

Key Features

• Genuine Mercury Marine 170-degree Fahrenheit thermostat
• Designed for precise temperature regulation in modern MerCruiser cooling systems
• Marine-grade construction built to handle heat, moisture, and vibration
• Compatible with dry joint exhaust and closed cooling systems
• Engineered for long service life and dependable operation
• Straightforward installation using common tools

Engine & Boat Compatibility

• Fits MerCruiser sterndrive engines: 4.3L, 4.5L, 5.0L, 5.7L, and 6.2L MPI
• Ideal for boats equipped with dry joint exhaust systems
• Works with closed cooling setups found on many cruisers and performance boats
• Common on runabouts, sport boats, family cruisers, tow boats, and workboats

Performance & Practical Benefits

A thermostat may seem like a small component, but you feel it in every part of your time on the water. With the correct 170-degree setting, your engine reaches operating temperature quickly, helping fuel burn cleaner and improving throttle response. Once warmed up, it stays remarkably steady—no temperature swings, no sluggish behavior, just a smooth, predictable rhythm that feels right under your hands.

This thermostat is engineered to open and close with precise timing, giving you a more controlled cooling cycle that’s especially helpful when navigating between idle zones and higher-speed stretches. The tight, secure fit of this OEM part ensures proper sealing, preventing the headaches that come from coolant leaks or thermal imbalance. And because it’s built from durable marine-grade materials, it stands up to the constant heat cycling and moisture that every sterndrive must endure.

Why Buy OEM

If you’ve been boating long enough, you already know the cooling system isn’t an area where you want surprises.

• OEM parts match Mercury’s original specifications exactly—no guessing
• Long-term reliability that protects your engine investment
• Better durability in marine environments than many aftermarket options
• Designed to fit right the first time, avoiding rework or misalignment
• Helps maintain proper engine temperature for smooth performance and reduced wear

It’s the kind of part you replace once, confidently, knowing it’s the right choice for your engine and your time on the water.

FAQ

Q1: Which engines does the Thermostat 864493 fit?

It fits MerCruiser 4.3L, 4.5L, 5.0L, 5.7L, and 6.2L Multi-Port Injection engines with dry joint exhaust and closed cooling systems.

Q2: What makes this thermostat better than aftermarket options?

Its accuracy, material quality, and precise opening temperature match Mercury’s engineering, giving your engine the temperature stability it needs.

Q3: How do I know if this is the correct replacement for my setup?

Check your engine model, cooling system type, and confirm you need a 170-degree thermostat—these details will match perfectly with this part number.

Q4: Can it be used in both saltwater and freshwater?

Yes. Its marine-grade construction is built to perform well in any environment.

Q5: Is installation straightforward?

Very. Most boat owners with basic tools and a service manual find the process simple and quick.