Mercury – Water Pump Impeller | OptiMax Cooling System | Elastomer Vanes | 89984T4

Overview

If you run a Mercury OptiMax 2.5-liter outboard, you already know these engines like to work. They’re crisp, responsive, and built to cover water fast but only when they’re getting a solid stream of cooling water. When the telltale weakens or the engine starts running warmer than usual, that’s your signal the impeller is wearing down. The Quicksilver 89984T4 Water Pump Impeller restores that confidence. It’s a small part with a big responsibility, and installing a fresh OEM impeller brings back the steady, reliable cooling flow your OptiMax depends on every single trip.

Key Features

• OEM water pump impeller designed specifically for Mercury OptiMax 2.5 L non-Pro outboards
• Fits engines with serial numbers 1B227000 and above
• High-flexibility elastomer vanes maintain proper water flow in hot and cold conditions
• Reinforced center insert resists tearing, separation, and hub slip
• Engineered for high, consistent cooling output under heavy load
• Built to Mercury Marine’s original specifications for correct fit and long-term durability

Engine & Boat Compatibility

This impeller is designed for:

• Mercury OptiMax 2.5 L non-Pro outboards
  • Serial number range: 1B227000 and up

Common on a wide variety of hulls, including:

• Bass boats
• Bay and flats boats
• Performance fishing rigs
• Multi-species boats
• Utility tiller setups
• Lightweight fiberglass and aluminum sport boats

OptiMax engines run lean and efficient, which means they rely heavily on consistent cooling. Using the correct OEM impeller is essential for their long-term health.

Performance & Practical Benefits

A worn impeller doesn’t fail all at once — it gradually loses flexibility. As the vanes stiffen or develop small cracks, they push less water through the cooling system. That translates to higher engine temperatures, rougher idling, and potential long-term damage if ignored.

The 89984T4 impeller brings the cooling system back to full strength. Its elastomer vanes sweep smoothly against the pump housing, pushing a tight, steady column of water that keeps your OptiMax running cool even during long, high-RPM runs. The reinforced insert is bonded firmly to the vanes, preventing separation under load — a common issue with cheap aftermarket alternatives.

On the water, the benefits show up immediately:

• A stronger telltale
• More stable engine temperatures
• Better idle quality
• Improved overall reliability

If you fish shallow lakes, chase tides, or run through debris-prone waters, replacing your impeller regularly isn’t optional — it’s essential. This OEM part gives your engine the protection it was engineered for.

Why Buy OEM

OptiMax engines are high-output, high-precision systems, and Mercury engineers designed the cooling flow around a specific impeller stiffness, vane spacing, and hub strength. Aftermarket parts might “fit,” but they rarely match the exact performance profile. An OEM Quicksilver impeller ensures proper water volume, better durability, and fewer surprises out on the water. For an engine as valuable as an OptiMax, OEM is simply the safest choice.

FAQ

Q1: Which engines does this impeller fit?

It fits Mercury OptiMax 2.5 L non-Pro outboards with serial numbers 1B227000 and above.

Q2: Why is OEM better for OptiMax models?

OEM impellers maintain the correct flow rate the OptiMax system requires, preventing overheating and long-term engine wear.

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

Check your engine’s serial number or refer to your Mercury owner’s manual for the correct part number.

Q4: Can it be used in saltwater?

Yes — just flush after each saltwater trip for best longevity.

Q5: Is installation easy?

Most boat owners can replace the impeller with basic tools and a service manual.

• Supersessions
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