Mercury – Thermostat Assembly | V12 Verado & SeaPro Series | Composite & Stainless Components | 8M0177662

Overview

When you run a boat powered by one of Mercury’s V12 giants, you get used to a certain level of confidence. You expect the throttle response to be instant, the temperature to stay steady, and the engine to feel as calm at idle as it does tearing across open water. A big part of that trust comes from the cooling system doing exactly what it should — quietly, consistently, in the background. The Mercury 8M0177662 Thermostat Assembly is one of those components you rarely see but rely on every single time you turn the key. Knowing that your engine is protected from overheating brings a kind of peace you can feel, whether you’re pushing offshore or cruising home against a late-afternoon chop.

Key Features

• Complete thermostat assembly designed for precise temperature regulation
• Includes top and bottom housings, 160°F thermostat, 140°F thermostat, spring, retainer, gasket, O-ring, plate, and hardware
• Built with heat-resistant materials and corrosion-resistant components
• Ensures stable operating temperature under varying loads and conditions
• Exact-fit OEM replacement for select Mercury V12 engines

Engine & Boat Compatibility

This Mercury Marine part is designed for:

• Mercury 7.6L V12 600hp Verado outboards
• Mercury 7.6L V12 500hp SeaPro outboards
• Serial number range: 3B060047–3B332191

Common boat applications include:

• Large offshore center consoles
• Commercial and patrol vessels
• Heavy-duty charter boats
• Multi-engine fishing platforms

Performance & Practical Benefits

On a V12 outboard, temperature control isn’t just about avoiding overheating — it’s about keeping the engine in the sweet spot where fuel burns cleanly, power comes smoothly, and internal components last as long as they should. With the 8M0177662 thermostat assembly installed, you’ll notice your engine settling into a steady rhythm. Warm-up happens predictably. Running temperatures stay consistent whether you’re cruising at midrange or dropping back to idle near the dock.

A worn or sticking thermostat can cause frustrating surges, reduced efficiency, and sometimes performance alarms that cut your day short. This OEM assembly restores the tight, confident feel you expect from a Mercury V12. The dual-thermostat setup manages temperature transitions with a smoothness you can feel in the helm controls — especially during long runs or when shifting frequently between low and high load.

Installation is straightforward with the included hardware, and once it’s in place, you’ll have the reassurance that your outboard is circulating coolant exactly the way Mercury engineered it to.

Why Buy OEM

High-horsepower outboards demand precision. A thermostat that’s just slightly off in temperature rating, response time, or fitment can change how the engine behaves, especially over long days in fluctuating conditions.

Choosing a genuine Mercury Marine thermostat assembly means:

• Accurate temperature regulation tailored to the V12 platform
• Materials tested against real-world marine heat cycles
• Longer service life than generic alternatives
• Guaranteed compatibility with the cooling passages and housings
• Confidence that your engine is protected the way Mercury intended

When you’re running a V12, the stakes are high — OEM is the only choice that truly protects your investment.

FAQ

Q1: Which Mercury engines does this thermostat assembly fit?

It fits Mercury 7.6L V12 600hp Verado and 500hp SeaPro outboards within the listed serial range.

Q2: What makes this different from aftermarket thermostats?

OEM components match exact temperature specs and materials designed for the V12’s extreme operating environment.

Q3: How do I confirm this is the correct replacement?

Match your engine model and serial number with your operator’s manual or parts diagram.

Q4: Is it suitable for both freshwater and saltwater use?

Yes — the materials are engineered for full marine exposure.

Q5: Is installation straightforward?

Most technicians and experienced boaters will find the assembly intuitive with standard tools.