Mercury – 170 Degree Thermostat | Cooling System Component | Brass & Stainless Steel | 8M0045990

Overview

There’s a certain comfort that comes from knowing your engine is running at the temperature it was born to run at. When you’re easing out of the no-wake zone or pushing across open water with a full day ahead, you don’t want to wonder whether your cooling system is keeping up. A reliable thermostat is one of those quiet heroes—rarely seen, hardly ever talked about, but always working in the background to keep things steady. That’s the feeling the Mercury 170-Degree Thermostat gives you: easy confidence, the kind you only get from gear that does exactly what it’s supposed to, every single time.

Key Features

• Regulates engine temperature at 170 degrees Fahrenheit
• Constructed with durable brass and stainless steel components
• Designed for long, dependable service life in harsh marine conditions
• Direct replacement built to exact Mercury Marine specifications
• Simple installation with standard hand tools

Engine & Boat Compatibility

• MerCruiser 8.2L Magnum sterndrive engines
• MerCruiser 8.2L EC inboard engines
• Common on a wide range of boats including:
  • Offshore fishing boats
  • Sport cruisers
  • Performance boats
  • Family runabouts and weekend cruisers

Performance & Practical Benefits

A good thermostat doesn’t just control temperature—it sets the rhythm for your entire engine. With this Mercury Marine part, your engine warms up smoothly, settles into a steady idle, and maintains consistent cooling even when you’re running hard in choppy conditions. You’ll feel the difference in how the throttle responds, how cleanly the engine holds its temperature, and how much less you worry about overheating when you’re miles from the dock.

The brass and stainless steel construction gives the thermostat a firm, reassuring weight and durability that holds up against constant heat cycling. There’s no rattle, no looseness—just a tight, secure fit that feels right during installation. Once in place, it resists corrosion, saltwater exposure, and the kind of thermal stress that can wear down cheaper aftermarket parts. Maintenance becomes easier too, because a stable cooling system helps reduce carbon buildup and keeps your engine running cleaner over time.

Why Buy OEM

Choosing an OEM thermostat isn’t about being fancy—it’s about being smart. Mercury designs its cooling components to work in harmony with the entire engine system, which means this thermostat fits perfectly and responds exactly as your engine expects. You won’t be wrestling with questionable dimensions or worrying about whether it’ll hold the correct temperature.

You also save money in the long run. A genuine Mercury Marine part lasts longer, protects the engine better, and helps prevent costly repairs caused by overheating or inconsistent cooling. If you’re the kind of boater who values reliability and peace of mind, OEM is simply the way to go.

FAQ

Q1: Which Mercury engines does this thermostat fit?

It fits MerCruiser 8.2L Magnum and 8.2L EC sterndrive and inboard engines.

Q2: What makes this different from aftermarket thermostats?

It’s engineered to Mercury Marine’s exact temperature and fitment specs, ensuring precise control and long-term durability.

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

Check your engine’s owner’s manual for a 170-degree thermostat callout and match it with part number 8M0045990.

Q4: Can this thermostat be used in both saltwater and freshwater?

Absolutely—it’s built with marine-grade materials designed to resist corrosion in both environments.

Q5: Is installation straightforward?

Yes, most boat owners can replace it with common hand tools and basic mechanical knowledge.