47-89980 47-68988 Water Pump Impeller for Mercury Mariner 3.5HP 3.6HP 4HP 4.5HP 7.5HP 9.8HP | JLM Marine

Water Pump Impeller for Mercury Mariner 3.5HP 3.6HP 4HP 4.5HP 7.5HP 9.8HP Outboard Engines

This high-quality aftermarket water pump impeller is designed to fit Mercury and Mariner 1-cylinder, 2-stroke outboard engines ranging from 3.5 HP to 9.8 HP, manufactured between 1979 and 1985. Engineered with a neoprene body and brass hub, this impeller ensures reliable cooling system performance for your outboard motor.

This impeller directly replaces Mercury Marine OEM part numbers 47-89980 and 47-68988, as well as Sierra Marine 18-3054. It features a 0.438-inch internal shaft diameter—verify your original impeller's shaft diameter before ordering, as Mercury engines use two different shaft sizes.

• Constructed from durable neoprene with a brass hub for long-lasting performance
• Features 6 blades for efficient water circulation
• Critical Note: This impeller is designed for shafts with 0.438" internal diameter only—NOT compatible with 0.456" shafts (such as 5HP models)

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

• 1 × Outboard Water Pump Impeller (Neoprene with Brass Hub)

Note: Lubricant (silicone grease, glycerine, or dish soap) is required for installation but is not included in the package.

Installation Guide

1. Disconnect the fuel line and remove the lower unit from your outboard motor following the manufacturer's service manual.
2. Remove the water pump housing cover and take note of the orientation of the old impeller before removal.
3. Carefully remove the old impeller from the pump housing, inspecting the housing and wear plate for damage or excessive wear.
4. Clean the pump housing thoroughly, removing any debris, old gasket material, or buildup.
5. Apply a generous amount of silicone grease, glycerine, or dish soap to the new impeller blades and inside the pump housing.
6. Insert the new impeller into the housing, ensuring the blades are oriented in the correct rotation direction (typically counterclockwise when viewed from above).
7. Rotate the drive shaft gently while pressing the impeller down to seat it fully onto the shaft.
8. Install a new gasket and replace the water pump housing cover, torquing bolts to the manufacturer's specifications.
9. Reinstall the lower unit onto the outboard motor, ensuring all fasteners are properly tightened.
10. Reconnect the fuel line and perform a water pressure test to confirm proper coolant flow.
11. Run the engine in a test tank or on-water and verify that the telltale (pee stream) is functioning normally.

Troubleshooting & FAQ

Q: How do I confirm this impeller fits my Mercury or Mariner engine?
A: First, verify your engine model and serial number against the compatibility table above. Most importantly, measure the internal diameter of your current impeller's center hole—this impeller is designed for a 0.438-inch shaft diameter only. If your impeller measures 0.456 inches, you need part number 47-89981 instead.

Q: Will this impeller fit my Mercury 5HP outboard?
A: No. Mercury 5HP engines use a larger shaft diameter (0.456 inches). This impeller is only compatible with engines that have a 0.438-inch shaft diameter. Using the wrong size will result in poor fit and potential cooling system failure.

Q: How often should I replace my water pump impeller?
A: It's recommended to replace your impeller every 2–3 years or every 200–300 hours of operation, whichever comes first. If you notice overheating, weak telltale flow, or the engine has been run dry, inspect and replace the impeller immediately.

Q: What are the signs that my impeller is failing?
A: Common symptoms include weak or absent water flow from the telltale (pee hole), engine overheating, steam from the engine, or loss of power. If you experience any of these, shut down the engine immediately and inspect the impeller.

Q: Do I need any special tools or lubricant to install this impeller?
A: You'll need basic hand tools to remove the lower unit and water pump housing. For installation, lubricate the impeller with silicone grease, glycerine, or dish soap (not included). Avoid petroleum-based lubricants, as they can damage the neoprene material.

Q: Is this an OEM or aftermarket impeller?
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.