Mercury – Impeller Key | Cooling System Component | Stainless Steel | 8M0032831

Overview

There are a few pieces on an outboard that don’t look like much at first glance, yet you realize just how vital they are the moment something goes wrong. The impeller key is one of those quiet heroes. It’s a small part, sure, but when you’re pushing across a glassy bay at sunrise or easing into a tight slip after a long day on the water, you want every single component in your cooling system doing its job without hesitation. This one gives you that peace of mind. It locks into place, stays put, and keeps your engine’s cooling water flowing exactly the way it should.

Key Features

• Securely anchors the impeller to your outboard’s driveshaft
• Constructed from long-lasting Stainless Steel for dependable strength
• Precision-machined to Mercury Marine part specifications
• Designed specifically for cooling-system stability and consistent water flow

Engine & Boat Compatibility

• Fits Mercury 3-cylinder 30–40 horsepower FourStroke outboards
• Fits Mercury 4-cylinder 40–60 horsepower EFI FourStroke outboards
• Ideal for a wide range of boats including fishing skiffs, small pontoons, aluminum runabouts, and utility boats
• Perfect for everyday recreational use as well as workboat duty

Performance & Practical Benefits

What makes this tiny part so important is how it affects your engine’s cooling rhythm. With a proper impeller key in place, the impeller spins exactly as it should — not slipping, not hesitating, just smooth, steady rotation that sends cooling water through the system with confidence. You’ll notice it when your engine holds a consistent temperature on a long run or when you’re idling through a no-wake zone without a hiccup.

Mercury designed this key with tight tolerances, so installation feels natural. It fits firmly without forcing, and once seated, it stays secure even when the conditions get rough. Stainless Steel construction means it resists corrosion whether you’re running in freshwater, brackish estuaries, or saltwater coastlines. That’s the kind of durability you appreciate after years of weekend trips and seasonal service intervals.

Why Buy OEM

When you rely on your boat as much as most of us do, cutting corners on critical engine parts just isn’t worth it.

With an authentic Mercury Marine part:

• You’re getting a component engineered for exact fitment
• Long-term reliability saves money and avoids mid-season breakdowns
• It works seamlessly with every other Mercury component around it
• You avoid the guesswork that comes with aftermarket alternatives
• It installs right the first time — no reshaping, adjusting, or troubleshooting

This is one of those small pieces where genuine parts make a big difference.

FAQ

Q1: Which Mercury engines does the Impeller Key 8M0032831 fit?

It fits Mercury 3-cylinder 30–40 horsepower and 4-cylinder 40–60 horsepower EFI FourStroke outboards.

Q2: What makes this different from aftermarket keys?

The fit is more precise, the Stainless Steel quality is higher, and it’s engineered to match the exact rotation demands of Mercury’s cooling systems.

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

If your engine falls within the model ranges above, this is the correct key. You can also match it by part number.

Q4: Can it be used in saltwater?

Absolutely — the Stainless Steel design resists corrosion in fresh and saltwater.

Q5: Is installation straightforward?

Yes. Most boaters install it during a routine impeller service with basic tools.