Water Pump Impeller – Fits Mercury/Tohatsu 8-20 HP 4-Stroke Outboards (Replaces 47-803748)

Water Pump Impeller – Fits Mercury/Tohatsu 8-20 HP 4-Stroke Outboards

This aftermarket water pump impeller is designed for consistent performance in a wide range of outboard motors, serving as a direct replacement for several OEM parts. It is compatible with select Mercury/Tohatsu 4-Stroke outboards from 8 to 20 HP (2003 and newer), including Command Thrust models, as well as certain Honda 4-Stroke and Tohatsu 2-Stroke applications.

Engineered from durable, high-strength neoprene rubber with a hardened nylon insert, this impeller ensures reliable water circulation to prevent overheating. It is a crucial component for maintaining engine cooling system efficiency and longevity.

• Installation Method: Direct replacement with key/keyway
• Includes: 1 Water Pump Impeller & 1 Impeller Key
• Material: 8-Blade Neoprene rubber with hardened nylon hub

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.

Confirm your engine model/year in the table below. For Johnson/Evinrude owners, here’s a guide to help you identify your engine’s serial/model: Johnson Serial Number Guide.

Confirm your engine model/year in the table below.

Mercury/Mariner Models

Tohatsu/Nissan Models

Honda Models

Evinrude/Johnson Models

Technical Specifications

Package Contents

• 1 x Water Pump Impeller (Replaces 47-803748)
• 1 x Impeller Key (Replaces 28-803749)

Explosion Diagram

Installation Guide

1. Safety First: Disconnect the battery and remove the propeller before beginning.
2. Drain Gearcase Oil: Place a drain pan under the lower unit and remove the upper and lower drain screws to drain the gearcase lubricant.
3. Remove Lower Unit: Remove the bolts securing the lower unit (gearcase) to the engine's midsection. The number and location of bolts vary by model.
4. Access the Impeller: With the lower unit removed, locate the water pump housing (typically a metal or plastic cover) and unbolt it.
5. Replace Impeller: Note the orientation of the old impeller's blades. Remove the old impeller and the key. Install the new key and slide the new impeller onto the drive shaft, turning the shaft clockwise to bend the blades correctly.
6. Reassemble: Reinstall the water pump housing, gaskets, and seals. Ensure a tight seal.
7. Reinstall Lower Unit: Guide the lower unit back into place, ensuring the driveshaft, shift shaft, and water tube align. Secure with bolts.
8. Refill Oil & Test: Refill the gearcase with fresh lubricant. Reconnect the battery, start the engine in water, and confirm water is exiting the "telltale" port.

Troubleshooting & FAQ

Q: How do I know if this impeller fits my engine?

A: The best way to confirm fitment is by matching your old part number to the ones listed in our cross-reference table. While this part fits a wide range of Mercury, Tohatsu, and Honda models, please check the specific compatible models listed. For Mercury, note that some applications are specific to Command Thrust (209cc) models.

Q: What are the signs of a failing water pump impeller?

A: Common signs include the engine overheating at idle or low speeds, a weak or non-existent water stream from the "telltale" indicator, or a melted water pump housing. The impeller blades can become brittle, stiff, or break over time.

Q: How often should I replace my outboard's impeller?

A: As a general rule, it is recommended to replace the water pump impeller every 1-2 years or every 100-200 hours of use, whichever comes first. This interval can be shorter if you frequently operate in sandy, silty, or saltwater environments.

Q: OEM vs. Aftermarket?

A: 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.

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

A: 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.

Q: What is your warranty and return policy?

A: 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.