Mercury 300-Hour Service Kit – Fits Mercury/Mariner 15-20 HP EFI FourStroke Outboards (8M0151470)

Mercury 300-Hour Service Kit – Fits Mercury/Mariner 15-20 HP EFI FourStroke Outboards (8M0151470)

This 300-hour service kit is designed for Mercury/Mariner 9.9, 10, 15, and 20 HP EFI FourStroke outboard engines with serial numbers 0R833820 and up (approximately 2015 and newer). It bundles all the necessary components to perform the manufacturer-recommended 300-hour maintenance schedule, ensuring your engine remains reliable and efficient.

This kit is a direct replacement for Mercury OEM part number 8M0151470.

• Includes all required filters, seals, gaskets, and anodes for a complete service.
• Components meet or exceed OEM specifications for fit and performance.
• Contains a complete water pump impeller repair kit and a new thermostat.

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 x Oil Filter (35-8M0162831)
• 1 x Fuel Filter (35-8M0134466)
• 1 x Oil Drain Seal (803752)
• 2 x Gearcase Drain Seals (12-895146, 8M0082880)
• 1 x Thermostat (8M0139434)
• 1 x Thermostat Gasket (27-8M0214960)
• 1 x Water Pump Repair Kit (46-8M0135821)
• 2 x Spark Plugs - NGK DCPR6E (803507)
• 2 x Anodes (823913Q)
• 2 x Anodes (97-875208)
• 1 x Impeller (8M0135803)
• 1 x Impeller Housing (8M0134492)
• 1 x Impeller Housing Base (8M0134493)
• 1 x Seal (8036674)
• 1 x Impeller Key (8M0137347)
• 1 x Cotter Pin (8150264)
• 1 x Plate 1 (8M0135805)
• 1 x Gasket 1 (8M0135804)
• 1 x Gasket 2 (8M0135806)
• 1 x Insert Cup (803751)

Installation Guide

1. Prepare the Engine: Ensure the engine is turned off, cooled down, and positioned securely on a level surface.
2. Drain Fluids: Drain the engine oil and gearcase lubricant, replacing the drain seals with the new ones provided.
3. Replace Filters: Remove and replace the old oil filter and fuel filter with the new ones from the kit.
4. Service Water Pump: Disassemble the lower unit to access the water pump. Replace the impeller, housing, gaskets, and seals using the included water pump repair kit components.
5. Replace Thermostat: Locate and replace the thermostat and its gasket to ensure proper engine operating temperature.
6. Change Spark Plugs: Remove the old spark plugs and install the new ones, ensuring they are gapped correctly.
7. Inspect and Replace Anodes: Check the existing anodes for corrosion and replace them with the new ones provided in the kit.
8. Refill Fluids: Refill the engine with the correct grade of oil and gearcase lubricant according to your owner's manual.
9. Final Checks: Inspect all connections and ensure all components are securely fastened before starting the engine.

Troubleshooting & FAQ

How do I confirm this kit fits my engine?
This kit is specifically for Mercury/Mariner 9.9 HP to 20 HP EFI FourStroke models. The most important factor is your engine's serial number. It must be 0R833820 or higher. For the 9.9 HP model, the serial number should be 1R008146 or higher.

How often should I use this service kit?
This kit is designed for your engine's 300-hour service interval as recommended by the manufacturer. Regular maintenance at these intervals is critical for engine longevity and performance.

What are the signs that my engine needs this service?
Common indicators include the engine running rough, overheating alarms, reduced top speed or power, or difficulty starting. However, it is best to follow the scheduled 300-hour service interval regardless of symptoms to prevent issues.

Does this kit include everything I need for a 300-hour service?
Yes, this is a comprehensive kit containing the oil filter, fuel filter, oil and gearcase seals, a complete water pump repair kit, thermostat and gasket, spark plugs, and all necessary anodes for a standard 300-hour service.

OEM vs. Aftermarket?
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.