8M0251133 Water Pump Impeller Kit for Mercury 30HP 40HP | JLM Marine

8M0251133 Water Pump Impeller Kit for Mercury 30HP 40HP | JLM Marine

This comprehensive water pump impeller kit is engineered to fit Mercury 30HP and 40HP 3-cylinder carbureted outboard engines with 2:1 gear ratio configurations. Designed for models with short shaft and standard gearboxes, this kit ensures reliable cooling system performance across a wide range of serial numbers from 0G231123 through 1C018825.

This aftermarket replacement kit directly replaces OEM part number 8M0251133 and provides a complete service solution including the impeller, gaskets, wear plate, thermostat, fuel filters, oil filter, and gear oil pump—everything needed for a thorough cooling system and maintenance service.

• Complete 16-piece kit with impeller, thermostat, fuel filters, oil filter, and gear oil pump
• Fits Mercury 30HP and 40HP 3-cylinder carbureted models with 2:1 ratio gearboxes
• Includes all necessary gaskets, wear plate, and water tubes for proper 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 comprehensive kit includes 16 components for complete cooling system service and routine maintenance:

• 47-85089-10 Water Pump Impeller × 1
• 8M0032838 85119 Impeller Key × 1
• 821354-2 Wear Plate × 1
• 27-822189 Gasket × 1
• 27-822217 Gasket × 1
• 12-86645-1 Washer × 2
• 823547 1 Water Tube × 1
• 43023 Water Tube × 1
• 825212T02 Thermostat × 1
• 27-8M0177107 Gasket × 1
• 35-877565T1 Fuel Filter × 1
• 35-8M0149607 Fuel Filter × 1
• 35-822626Q2 Oil Filter × 1
• 8M007119 Drain Gasket × 1
• 8M0204693 Drain Gasket × 2
• 24OP149 Gear Oil Pump × 1

Installation Guide

1. Disconnect the fuel line and remove the lower unit from the outboard motor following your engine's service manual procedures.
2. Remove the water pump housing bolts and carefully separate the housing from the driveshaft assembly. Inspect the housing for cracks or damage.
3. Remove the old impeller, impeller key, and wear plate from the pump housing. Clean all surfaces thoroughly, removing any debris or old gasket material.
4. Install the new wear plate into the pump housing, ensuring proper alignment with the mounting holes.
5. Lubricate the new impeller with glycerin or soapy water (never petroleum-based products). Insert the impeller key into the driveshaft slot.
6. Install the impeller onto the driveshaft, rotating the blades in the correct direction (typically clockwise when viewed from above). Ensure the impeller key seats properly.
7. Replace the water tubes with the new ones provided (part numbers 823547 1 and 43023), checking for proper fit and no obstructions.
8. Install new gaskets (27-822189, 27-822217, and 27-8M0177107) on all mating surfaces. Do not reuse old gaskets.
9. Replace the thermostat (825212T02) in its housing, ensuring the temperature-sensing element faces the correct direction per your service manual.
10. Reassemble the water pump housing to the lower unit using the washers (12-86645-1) and tighten bolts in a cross-pattern to manufacturer specifications.
11. Reinstall the lower unit to the engine. Replace the fuel filters (35-877565T1 and 35-8M0149607) and oil filter (35-822626Q2) per your maintenance schedule.
12. Use the gear oil pump (24OP149) and new drain gaskets (8M007119 and 8M0204693) to change the lower unit gear oil. Run the engine with water supply and check for proper cooling stream.

Troubleshooting & FAQ

Q: How do I confirm this kit fits my Mercury engine?
A: Check your engine's serial number plate and compare it to the compatible ranges listed above (0G231123 through 1C018825). This kit fits 30HP and 40HP 3-cylinder carbureted models with 2:1 gear ratio gearboxes.

Q: How often should I replace the water pump impeller?
A: Mercury recommends replacing the water pump impeller annually or every 300 hours of operation, whichever comes first. Replace immediately if you notice reduced cooling stream or overheating.

Q: What are the signs my water pump impeller needs replacement?
A: Warning signs include weak or absent cooling water stream from the indicator, engine overheating, steam from the engine, or reduced water pressure. Impeller blades may become cracked, broken, or worn over time.

Q: Can I use petroleum-based lubricants when installing the impeller?
A: No, never use petroleum-based products on the impeller as they can damage the rubber. Use only glycerin, dish soap mixed with water, or dedicated impeller installation lubricant.

Q: Does this kit include everything I need for a complete water pump service?
A: Yes, this 16-piece kit includes the impeller, gaskets, wear plate, water tubes, thermostat, and even fuel filters, oil filter, and gear oil pump for comprehensive maintenance. You'll have all critical cooling system and service components in one package.

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.