Mercury – Replacement Thermostat | OptiMax 3.0L & V6 Series | Marine-Grade Brass & Stainless Components | 8M0057307

Overview

There’s a certain comfort in knowing your engine is running at the exact temperature it was designed for. When you’re cruising across open water or easing into a quiet cove, you want to feel that smooth, steady power beneath you—no hesitation, no surprises. The Quicksilver 8M0057307 130-Degree Fahrenheit Thermostat helps keep that feeling consistent. It maintains the cooling system temperature your OptiMax counts on, so every run feels controlled, confident, and right where it should be.

Key Features

• Precisely calibrated one-hundred-thirty-degree-Fahrenheit thermostat
• Marine-grade construction for long-term durability
• Self-cleaning design to shed debris and prevent sticking
• Ensures proper engine cooling temperature for performance and efficiency
• Easy installation with common tools
• Built to Mercury Marine original equipment specifications

Engine & Boat Compatibility

• Designed for three-point-zero-liter and V6 Mercury OptiMax outboards (non-Pro models)
• Fits model years two-thousand-one and newer with ECM 555 systems (check serial numbers 0M300000–2A455878)
• Ideal for bay boats, offshore center consoles, bass boats, and multi-species rigs powered by OptiMax outboards
• Suitable for both recreational and heavy-use applications

Performance & Practical Benefits

A thermostat might seem like a small component, but on the water, small things make big differences. This Mercury Marine part helps the engine warm quickly and stay at a tight, predictable temperature. You’ll feel that steadiness in the throttle response, the smooth idle, and the clean transition when you jump on plane.

Because it’s calibrated specifically for OptiMax cooling systems, the thermostat reacts exactly the way your engine expects—opening cleanly when temperatures rise and sealing firmly when it’s time to maintain heat. The self-cleaning surfaces help contaminants wash through instead of building up, which makes the system more reliable and reduces the chance of overheating after a long run through weedy or silty water.

Everything about it feels solid, steady, and secure. You install it once, and it quietly protects your engine trip after trip.

Why Buy OEM

With something as critical as engine temperature, shortcuts just don’t make sense. An aftermarket thermostat may look similar, but they rarely match Mercury’s calibration accuracy or durability. An OEM Mercury Marine part—notably this part number 8M0057307—is engineered for your exact outboard. It fits cleanly, responds correctly, and holds up season after season.

Choosing genuine Mercury parts means fewer surprises, fewer headaches, and more time actually enjoying your time on the water. For most boaters, that’s the simplest kind of logic.

FAQ

Q1: Which engines does the 8M0057307 thermostat fit?

It’s designed for three-point-zero-liter and V6 Mercury OptiMax outboards using ECM 555 controls.

Q2: What sets this apart from aftermarket versions?

Precise temperature calibration, longer-lasting materials, and a self-cleaning design—all matched to Mercury’s cooling system specifications.

Q3: How can I confirm it’s the correct thermostat for my engine?

Check your owner’s manual for the specified temperature rating, or match your engine’s model, year, and serial range.

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

Yes, its marine-grade construction is suited for either, provided regular maintenance is followed.

Q5: Is installation straightforward?

Most boaters comfortable with basic maintenance can replace it using common tools. Just follow the steps in your service manual.