Water Pump Impeller – Fits Mercury Marine 20 HP (Replaces 47-89982)

Water Pump Impeller – Fits Mercury Marine 20 HP (Replaces 47-89982)

This water pump impeller is designed for Mercury Marine 20 HP 2-stroke outboard engines manufactured between 1970 and 1985. It serves as a direct replacement for several OEM and aftermarket part numbers, ensuring a precise fit for restoring your engine's cooling system.

Engineered to meet or exceed original equipment specifications, this impeller is a critical component for preventing overheating. It is installed in the lower gearcase and driven by the driveshaft to pump raw water through the engine's cooling passages.

• Material Composition: Made with a durable neoprene rubber housing around a solid brass hub for corrosion resistance and longevity.
• Installation Location: Mounts inside the water pump housing on the lower gearcase unit.
• Included Hardware: A new drive key is typically included to ensure a secure fit on the driveshaft.

Part Number Cross-Reference

Use this table to confirm equivalent part numbers across OEM and aftermarket brands.

Compatible Engine Models

Confirm your engine model/year in the table below. For Mercury owners, here’s a guide to help you identify your engine’s serial/model: Mercury Serial Number Guide. You can also review exploded diagrams to verify part numbers: Mercury Parts Diagrams & Catalog.

Technical Specifications

Package Contents

Note: Package contents may vary by aftermarket brand. Most kits will contain the following essential components:

• 1 x Water Pump Impeller (replaces 47-89982)
• 1 x Drive Key

Depending on the manufacturer, some kits may additionally include:

• 1 x Face Plate
• 1 x Plate Gasket
• 1 x Slinger
• 1 x O-Ring

Installation Guide

1. Safety First: Disconnect the battery and remove the spark plug wires before starting work.
2. Drain Oil: Place a drain pan under the lower unit and remove the upper and lower gearcase oil drain screws to empty the oil.
3. Shift to Neutral: Make sure the engine is in the neutral gear position.
4. Remove Lower Unit: Loosen and remove the bolts securing the lower gearcase (lower unit) to the engine's midsection.
5. Separate Gearcase: Carefully lower the gearcase away from the engine. The driveshaft will slide out of the crankshaft.
6. Access Pump Housing: The water pump is located on top of the gearcase. Remove the bolts holding the water pump housing cover.
7. Remove Old Impeller: Lift the housing and slide the old impeller off the driveshaft. Be sure to remove the small drive key from the shaft.
8. Clean and Inspect: Clean any debris or corrosion from the housing interior and face plate. Inspect for scoring or warping that could cause leaks.
9. Install New Impeller: Install the new gasket, wear plate, and drive key. Slide the new impeller onto the driveshaft, twisting it in the direction of engine rotation to seat the vanes correctly.
10. Reassemble Pump: Reinstall the pump cover and tighten the bolts to the manufacturer's specified torque.
11. Reinstall Lower Unit: Carefully guide the driveshaft and water tube into position while raising the lower unit. Secure it with the mounting bolts.
12. Refill Oil: Refill the gearcase with fresh marine gear lube until it flows from the upper vent hole, then reinstall both drain screws.

Troubleshooting & FAQ

How do I confirm this impeller fits my Mercury engine?

This impeller fits the Mercury 20 HP (Model 200) 2-stroke outboard produced from 1970 to 1985. The best way to verify fitment is to match your old part's number to one listed in our cross-reference table, such as 47-89982, 47-89982B, or aftermarket numbers like Sierra 18-3052.

What are the signs of a failing water pump impeller?

Common signs include your engine overheating, a weak or intermittent water stream from the "tell-tale" outlet, or discovering bits of rubber impeller material clogging the cooling passages during inspection.

How often should I replace the water pump impeller?

For preventative maintenance, it is recommended to replace the impeller every 1-2 years or every 100-200 hours of use. Frequency should increase if you operate primarily in saltwater or sandy/silty conditions.

OEM vs. Aftermarket?

This listing is an aftermarket replacement part (not an OEM component). We build to OEM specifications using comparable-grade materials. Production is done in an ISO9002-certified facility, and each batch is inspected for consistent performance.

How fast do you ship and how much does it cost?

We offer fast global shipping—typically 5–15 days worldwide—and standard shipping is free. Expedited options are available at checkout depending on your location.

What is your warranty and return policy?

This product includes a 1-year warranty against manufacturing defects under normal use. If something goes wrong, contact our support team with your order details. Returns are accepted within our standard return window (unused & in original condition); please see our policy page or reach out for instructions.

Important Notes

• Verify that the product images and specifications match your original part. If discrepancies exist—even if your model is listed—do not proceed with the purchase.
• This product is an aftermarket replacement part and is not an OEM component.
• Professional installation is recommended to ensure safety and optimal performance.

Why Choose JLM MARINE?

• Quality Assured: As a trusted manufacturer for over 20 years, we supply top marine brands globally.
• Fast Global Shipping: Free delivery worldwide in 5–15 days.
• Direct from Manufacturer: Competitive pricing without compromising quality.