8M0251125 Maintenance Kit for Mercury 30HP 40HP | JLM Marine

8M0251125 Maintenance Kit for Mercury 30HP 40HP | JLM Marine

This comprehensive maintenance kit is specifically designed for Mercury 30-40HP 2-Cylinder USA-made outboard engines manufactured between 1995 and 2007 (suits serial numbers starting with 0G, 0T, 1B, or 0P). It includes all essential components needed for a complete service—from water pump parts to fuel filters and gear oil pump—ensuring your engine runs smoothly and reliably season after season.

This aftermarket kit directly replaces Mercury OEM part number 8M0251125, providing a cost-effective solution without compromising on quality. Each component is manufactured to OEM specifications, offering dependable performance and extended service intervals.

• Includes water pump impeller, wear plate, gaskets, thermostat, fuel filters, and gear oil pump
• Complete service solution for routine maintenance in a single kit
• Designed for 2-cylinder Mercury engines with specific serial number ranges

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 maintenance kit includes the following components:

• 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
• 14586 Thermostat × 1
• 27-812867 2 Thermostat Gasket × 1
• 35-87946Q3 Fuel Filter × 1
• 35-879885T Fuel Filter × 1
• 12-191833 Drain Screw Gasket × 3
• 27-828816 Oil Drain Screw Gasket × 1
• 24OP149 Gear Oil Pump × 1

Important: Verify all components against your engine's service manual before installation to ensure proper fitment.

Installation Guide

1. Preparation: Disconnect the fuel line and remove the lower unit from the engine. Ensure the engine is cool and stabilized on a work stand.
2. Drain Fluids: Use the provided drain screw gaskets to remove and replace old gearcase oil. Dispose of fluids according to local regulations.
3. Remove Water Pump Housing: Unscrew the water pump housing bolts and carefully lift off the housing. Inspect for corrosion or damage.
4. Replace Impeller: Remove the old impeller using the impeller key, then install the new impeller (47-85089-10) ensuring blades face the correct direction.
5. Install Wear Plate: Position the new wear plate (821354-2) on top of the impeller. Ensure it sits flush and aligns with mounting holes.
6. Replace Gaskets: Install new gaskets (27-822189 and 27-822217) on the housing and base plate. Apply a thin layer of marine grease for easier assembly.
7. Install Water Tubes: Insert the water tubes (823547 1 and 43023) into their respective ports, ensuring secure seating without kinks.
8. Replace Thermostat: Remove the old thermostat housing, install the new thermostat (14586) with its gasket (27-812867 2), and tighten bolts evenly.
9. Install Fuel Filters: Replace both fuel filters (35-87946Q3 and 35-879885T) in the fuel line. Ensure O-rings are properly seated to prevent leaks.
10. Reassemble Water Pump Housing: Carefully position the housing back onto the lower unit and torque bolts to manufacturer specifications in a cross pattern.
11. Refill Gearcase Oil: Use the gear oil pump (24OP149) to refill the lower unit with fresh gear oil until it flows from the upper vent hole.
12. Final Check: Reconnect the fuel line, reattach the lower unit, and run the engine in a test tank to verify proper water flow and operation.

Troubleshooting & FAQ

Q: How do I confirm this kit fits my Mercury outboard?
A: Verify your engine is a 30-40HP 2-cylinder USA-made model from 1995-2007 with a serial number starting with 0G, 0T, 1B, or 0P. Cross-reference your engine's serial number using the Mercury Serial Number Guide linked above.

Q: How often should I perform this maintenance service?
A: Mercury recommends replacing the water pump impeller and related components annually or every 100 hours of operation, whichever comes first. Fuel filters and thermostats should be inspected and replaced as needed during routine service.

Q: What are signs my water pump impeller needs replacement?
A: Common symptoms include reduced water flow from the tell-tale indicator, engine overheating, steam from the engine cover, or visible damage to impeller blades during inspection. Never run the engine dry, as this accelerates impeller wear.

Q: Can I use this kit if my engine serial number doesn't match the specified range?
A: No, this kit is engineered specifically for engines with serial numbers starting with 0G, 0T, 1B, or 0P. Using incompatible parts may result in improper fitment, reduced performance, or engine damage.

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.