Mercury – Impeller Key | Cooling System Components | Marine Alloy | 8M0173458

Overview

There’s a quiet confidence that settles in when you know your outboard’s cooling system is doing exactly what it should. You feel it when you ease away from the dock, when you push the throttle a little harder against the chop, and when you settle into that familiar steady hum offshore. A small part like the impeller key doesn’t get much attention, but when it’s right, everything just works — smooth, predictable, and dependable. The Mercury 8M0173458 Impeller Key is one of those simple pieces that keeps the heart of your engine’s cooling system turning, giving you the peace of mind every boater wants out on the water.

Key Features

• Replacement impeller key designed for Mercury cooling-water impeller systems.
• Durable marine-grade alloy construction.
• Includes impeller key and washer for a complete replacement.
• Engineered for a tight, secure fit that maintains proper impeller rotation.
• Built to Mercury Marine original equipment specifications.

Engine & Boat Compatibility

This Mercury Marine part fits:

• Mercury TwoStroke carbureted outboards from 6–15 horsepower (serial numbers 0A19112–0T979999).
• Mercury 10hp Magnum, Marathon, SeaPro, and XR10 carbureted. outboards (serial numbers 0D038000–0T979999).
• Commonly used on jon boats, skiffs, small fishing boats, inflatables, dinghies, and lightweight tenders.

Performance & Practical Benefits

An impeller key may be small, but anyone who’s replaced one knows how important it is for the cooling system to stay in sync. This key locks the impeller securely in place, helping ensure steady water flow through the engine. When everything is aligned and rotating properly, you get a cooling stream that feels confident and consistent — the kind that gives you a reliable temperature gauge reading even after long runs.

Installation is straightforward, and you’ll feel the difference once the new key is seated and the housing goes back together. There’s a satisfying tightness to the fit, a smooth rotation that tells you the impeller is ready to do its job without slipping. Whether you’re trolling quietly through a backwater creek or running to your next fishing spot, that stable cooling flow protects the engine from overheating and keeps performance steady.

Saltwater, heat, and years of use can wear down a key faster than most boaters realize. Replacing it proactively saves headaches later and keeps your outboard responding the way it’s meant to. With this marine-grade part, you’ll know the component handling one of your engine’s most important jobs is built to stand up to all the elements that come with the boating life.

Why Buy OEM

When it comes to small precision parts, Mercury’s original design matters. Aftermarket keys may look similar, but minor differences in hardness, shape, or machining can lead to slippage, premature wear, or poor alignment. A genuine Mercury Marine part ensures you’re using the same component engineered for your cooling system from day one.

It installs cleanly, seats properly, and holds up season after season. It’s the kind of smart choice experienced boaters make because it saves time, protects the engine, and avoids the frustration of cheap replacements that don’t fit quite right.

FAQ

Q1: Which engines does the Impeller Key 8M0173458 fit?

It fits Mercury 6–15hp TwoStroke carbureted outboards and 10hp Magnum, Marathon, SeaPro, and XR10 models within the listed serial ranges.

Q2: What makes this different from aftermarket keys?

OEM keys match exact Mercury dimensions and materials, ensuring secure impeller engagement.

Q3: How do I confirm it’s the correct replacement?

Check your engine’s horsepower, model type, and serial-number range against the compatibility list.

Q4: Can it be used in saltwater and freshwater?

Yes — the alloy is built for marine use in all environments.

Q5: Is installation straightforward?

Most boat owners can replace it with standard tools, especially if they’ve done impeller service before.