8M0251120 Annual Maintenance Kit for Mercury 6HP 8HP 9HP 15HP | JLM Marine

8M0251120 Annual Maintenance Kit for Mercury 6HP 8HP 9HP 15HP | JLM Marine

This comprehensive annual maintenance kit is engineered for Mercury 6HP, 8HP, 9HP, and 15HP outboard engines with twist & pull choke type and integral gear/throttle tiller configuration. It provides all essential components needed for routine service and ensures your engine continues to deliver reliable performance season after season.

Direct OEM Replacement: 8M0251120. This kit consolidates critical maintenance parts into one complete package, simplifying your annual service routine and reducing downtime.

• Includes 22 individual components: impeller, seals, gaskets, thermostat, fuel filter, anode, and gear oil pump
• Designed for twist & pull choke type engines with integral gear/throttle tiller
• Complete all-in-one solution for annual maintenance intervals

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 annual maintenance kit includes the following 22 components:

• 46-42040A5 Housing × 1
• 12-191833 Drain Screw Gasket × 3
• 27-19202 Gasket × 1
• 27-19204-3 Gasket × 1
• 26-413651 Oil Seal × 2
• 47-42038-2 Impeller × 1 (critical wear component)
• 12-16448 Gasket × 2
• 19643 Gasket × 2
• 42200 Plate × 1
• 42089A2 Housing × 1
• 421021 Seal × 1
• 42376A2 Key × 1
• 10-48408 Screw × 1
• 42375 Plate × 1
• 26-33613 Seal × 1
• 26-42133 Seal × 1
• 25-822236 Seal × 1
• 14586A3 Thermostat × 1
• 35-87946Q3 Fuel Filter × 1
• 27-828816 Oil Drain Screw Gasket × 1
• 42121A2 Anode × 1
• 24OP149 Gear Oil Pump × 1

Installation Guide

1. Preparation: Gather all tools, fresh gear oil, and verify all kit components are present before starting. Ensure the engine is cool and positioned upright.
2. Drain Lower Unit: Remove the lower drain screw and upper vent screw to fully drain old gear oil into a suitable container. Inspect oil for metal particles or milky appearance indicating water intrusion.
3. Replace Drain Screw Gaskets: Install new drain screw gaskets (12-191833 and 27-828816) on both drain and vent screws.
4. Remove Water Pump Housing: Disconnect the lower unit and remove bolts securing the water pump housing (46-42040A5). Carefully separate the housing to access the impeller.
5. Install New Impeller: Remove the old impeller (47-42038-2) and key (42376A2), then install the new impeller with the key in the correct orientation. Apply a thin coat of glycerin or soapy water to ease installation.
6. Replace Seals and Gaskets: Install all new seals (26-413651, 421021, 26-33613, 26-42133, 25-822236) and gaskets (27-19202, 27-19204-3, 12-16448, 19643) in their respective locations. Ensure proper seating to prevent leaks.
7. Install Plates and Housing: Position the plate (42200) and reassemble the housing (42089A2) with the new plate (42375). Torque all fasteners to manufacturer specifications.
8. Replace Thermostat: Remove the old thermostat housing and install the new thermostat (14586A3) with fresh gaskets. Ensure proper orientation for correct opening temperature.
9. Install Fuel Filter: Locate the inline fuel filter and replace with the new unit (35-87946Q3). Ensure fuel line connections are secure and properly oriented.
10. Replace Anode: Remove the old sacrificial anode and install the new anode (42121A2). Torque to specification to ensure proper electrical contact.
11. Refill Gear Oil: Using the provided gear oil pump (24OP149), inject fresh gear oil through the lower drain hole until it flows from the upper vent hole. Install vent screw first, then drain screw immediately.
12. Final Checks: Reconnect the lower unit, run the engine in a test tank or on the water, and inspect for leaks or abnormal operation. Check water pump discharge for strong, consistent flow.

Troubleshooting & FAQ

How do I confirm this kit fits my Mercury engine?
Verify your engine has a twist & pull choke type with integral gear/throttle tiller. Check your engine's serial number plate; if it's a Japanese model starting with "0N," this kit is not compatible. For all other 6HP, 8HP, 9HP, and 15HP Mercury models (including Marathon & Seapro USA versions), cross-reference your current parts with the kit contents listed above.

How often should I perform this annual maintenance?
Mercury recommends annual service or every 100 hours of operation, whichever comes first. If you operate in saltwater, sandy conditions, or run your engine frequently, consider servicing every 50–75 hours to maximize longevity.

What are the signs that my impeller or seals need replacement?
Watch for weak or intermittent water flow from the cooling outlet, engine overheating, steam from the powerhead, or visible impeller blade damage during inspection. Gear oil that appears milky or contains metal shavings indicates seal failure and requires immediate attention.

Can I install this kit myself or do I need a professional?
Mechanically inclined owners with proper tools can complete this service following the manual. However, proper torque specs, seal orientation, and lower unit reassembly are critical; if you're unsure, professional installation ensures warranty compliance and prevents costly mistakes.

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

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

What is your warranty and return policy?
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.