Mercury – Water Pump Impeller | 4–6 HP Four-Stroke Series | Marine Elastomer Construction | 8M0204676

Overview

There’s a certain comfort in knowing your outboard is staying cool, no matter where the day takes you. When you’re running a small four-stroke — slipping along a quiet shoreline, pushing through a narrow creek, or heading back with the sun on your shoulders — you want that steady, reliable flow of cooling water you don’t have to think about. That’s exactly what this Mercury Marine part delivers. It’s the kind of component you rarely see but always feel, keeping your engine smooth, calm, and protected from the moment you start it.

Key Features

• Supplies essential cooling water to Mercury four-stroke outboards
• Marine-grade elastomer construction for long-lasting flexibility and strength
• Designed for Mercury four- to six-horsepower engines (serial 0R411838 and above)
• Engineered for higher flow rates and consistent cooling performance
• Built to Mercury Marine part number 8M0204676
• Replaces previous part number 161543
• Manufactured to OEM specifications for proper fit and efficiency

Engine & Boat Compatibility

• Fits Mercury four- to six-horsepower four-stroke outboards (serial 0R411838 and above)
• Ideal for lightweight jon boats, dinghies, tenders, inflatable boats, and small fishing craft
• Suitable for portable outboards used on lakes, rivers, protected coastal waters, and no-wake zones
• Works for both recreational and utility applications where dependable cooling is essential

Performance & Practical Benefits

A water pump impeller has one job — keep water moving through the engine — but you’ll feel the effect in every moment on the water. This impeller delivers a steady, secure flow that holds engine temperatures in the sweet spot, whether you’re idling quietly or running at full throttle. The elastomer blades flex smoothly without cracking, even through wide temperature swings from early-spring cold to late-summer heat.

Once installed, you’ll notice how stable the engine feels. Temperature stays predictable, the idle sounds smooth, and that nervous glance at the tell-tale stream becomes a thing of the past. The impeller seats with a tight, confident fit, turning cleanly with every rotation of the drive shaft. Even if you occasionally run through shallow areas or sandy bottom, the reinforced design holds up better than cheaper alternatives, resisting tearing and premature wear.

For boaters who rely on small engines, cooling failures are one of the quickest ways to ruin a day. This OEM impeller helps ensure the heart of your outboard keeps beating steady.

Why Buy OEM

Cooling components aren’t the place to cut corners. A genuine Mercury Marine part is built to match the exact flow rates, materials, and tolerances your engine was designed for. Aftermarket impellers may look similar, but slight differences in stiffness or blade shape can lead to low flow, overheating, or early breakdown — problems you don’t want to discover when you’re far from the ramp.

With OEM, you get the fitment, durability, and performance Mercury engineered with your four-stroke in mind. It’s long-term reliability wrapped in a simple part — and the kind of advice any seasoned boater would give: when it comes to cooling, stick with Mercury.

FAQ

Q1: Which Mercury engines does the Water Pump Impeller 8M0204676 fit?

It fits Mercury four- to six-horsepower four-stroke outboards with serial numbers 0R411838 and above.

Q2: What makes this impeller better than aftermarket versions?

It’s engineered to Mercury’s exact cooling specifications, using marine-grade elastomer materials that resist wear and maintain proper flow.

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

Check your outboard’s model and serial number. If it matches the four- to six-horsepower four-stroke range and calls for this part number, it’s the correct fit.

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

Yes — the materials are designed to hold up in both environments with proper maintenance.

Q5: Is installation straightforward for most boat owners?

Most boaters comfortable with basic outboard maintenance can install it using standard hand tools. The fit is tight, smooth, and predictable.