8M0251127 Water Pump Impeller Kit for Mercury 40HP 4-Cylinder | JLM Marine

8M0251127 Water Pump Impeller Kit for Mercury 40HP 4-Cylinder | JLM Marine

This comprehensive water pump impeller kit is engineered for Mercury 40HP 4-Cylinder outboard engines manufactured between 1989 and 1997 (serial numbers 0C159200 & up and 9570790 & up). Designed to deliver reliable cooling system performance, this kit includes all essential components for a complete pump rebuild.

OEM Reference: 8M0251127. This aftermarket replacement kit provides a cost-effective solution for maintaining optimal water flow and engine temperature regulation.

• Complete rebuild kit with 17 components including impeller, gaskets, seals, and pump base
• Includes bonus items: fuel filter, gear oil pump, and drain screw gaskets
• Ensures full cooling system restoration in a single installation

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

This complete kit includes 17 essential components for a comprehensive water pump rebuild:

• 47-89983 Water Pump Impeller × 1
• 8M0032837 Impeller Key × 1
• 32768 Wear Plate × 1
• 48753 Liner × 1
• 27-19553 Gasket × 1
• 27-19551 Gasket × 1
• 27-19552 Gasket × 2
• 37721001 Seal × 1
• 25-20273 Seal × 1
• 46-77822A1 Water Pump Base × 1
• 25-26722 O-Ring × 1
• 26-830749 Drain Plug Seal Gasket × 2
• 2530 O-Ring × 2
• 35-877565T1 Fuel Filter × 1 View Part →
• 12-191833 Drain Screw Gasket × 3 View Part →
• 27-828816 Oil Drain Screw Gasket × 1
• 24OP149 Gear Oil Pump × 1

Installation Guide

1. Preparation: Disconnect the fuel line and remove the lower unit from the outboard motor following your engine's service manual. Clean the mounting surface thoroughly.
2. Remove Old Components: Disassemble the old water pump housing, carefully extracting the worn impeller, gaskets, and seals.
3. Inspect Surfaces: Check the pump base and housing for corrosion, cracks, or scoring. Replace if damaged.
4. Install Wear Plate: Position the new wear plate (32768) onto the pump base, ensuring proper alignment.
5. Lubricate Impeller: Apply marine-grade grease to the new impeller (47-89983) blades for easier installation and initial lubrication.
6. Insert Impeller Key: Install the impeller key (8M0032837) into the drive shaft, then carefully install the impeller, bending blades in the correct rotation direction.
7. Install Liner and Seals: Place the liner (48753) over the impeller, then install the seals (37721001, 25-20273) in their designated grooves.
8. Apply Gaskets: Position all gaskets (27-19553, 27-19551, 27-19552) according to the service manual's exploded diagram.
9. Assemble Pump Base: Mount the water pump base (46-77822A1) and secure it with appropriate fasteners, torquing to manufacturer specifications.
10. Install O-Rings: Install the O-rings (25-26722, 2530) and drain plug seal gaskets (26-830749) in their respective locations.
11. Reinstall Lower Unit: Carefully align and reinstall the lower unit onto the motor, ensuring the drive shaft engages properly with the impeller.
12. Test Operation: Reconnect the fuel line, run the engine with a water supply (using a flush attachment or in the water), and verify proper water discharge from the tell-tale. Check for leaks around all gasket surfaces.

Troubleshooting & FAQ

Q: How do I confirm this kit fits my Mercury 40HP engine?
A: Verify your engine is a 4-cylinder model manufactured between 1989 and 1997 with serial number 0C159200 & up or 9570790 & up. Cross-reference the OEM part number 8M0251127 with your engine's service manual or parts diagram.

Q: How often should I replace my water pump impeller?
A: Mercury recommends replacing the water pump impeller every 2-3 years or 300 hours of operation, whichever comes first. If you notice overheating, reduced water flow from the tell-tale, or operate in sandy/debris-laden water, inspect and replace more frequently.

Q: What are the signs my water pump is failing?
A: Common symptoms include engine overheating, weak or no water stream from the tell-tale indicator, steam from the engine, or the overheat alarm sounding. Address these issues immediately to prevent engine damage.

Q: Does this kit include everything I need for a complete rebuild?
A: Yes, this comprehensive kit includes the impeller, wear plate, liner, all necessary gaskets, seals, O-rings, pump base, and bonus items like a fuel filter and gear oil pump. You'll have all components needed for a thorough water pump service.

Q: What's the difference between this aftermarket kit and the OEM version?
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.