Mercury – 300-Hour Maintenance Kit | 40–60HP FourStroke EFI Command Thrust | OEM Service Components | 8M0090559

Overview

Most boaters can tell you exactly where they were the first time their engine reminded them that maintenance matters. Maybe it was a sluggish start on a warm morning or a rough idle as you eased into the no-wake zone. Moments like that make you appreciate the value of doing things right — and doing them on time. The Mercury 8M0090559 300-Hour Maintenance Kit gives you everything you need to keep your 40–60 horsepower FourStroke EFI running smooth, steady, and ready for whatever water you love. It’s that sense of peace knowing your next season starts with fresh parts, clean filters, and the confidence that your engine is truly cared for.

Key Features

• Complete 300-hour service kit for Mercury four-cylinder 40–60HP FourStroke EFI outboards
• Designed for BigFoot and Command Thrust gearcases (serial number 1C000001 and up)
• Includes oil filter, low- and high-pressure fuel filters, oil drain seal, gearcase seals, thermostat and gaskets, four spark plugs, water impeller kit, and anodes
• Premium filters built with high pleat counts for superior fuel and oil filtration
• Heavy-duty electroplated housings help resist corrosion in harsh marine environments
• Provides all essential wear-item replacements in one convenient package

Engine & Boat Compatibility

• Fits Mercury 40–60 horsepower FourStroke EFI outboards
• Compatible with BigFoot and Command Thrust gearcases
• Ideal for pontoons, bay boats, aluminum fishing rigs, skiffs, runabouts, and general-use family boats
• Suited for engines with serial numbers 1C000001 and above

Performance & Practical Benefits

A proper 300-hour service can make your engine feel almost new again. The filters restore crisp fuel delivery and clean oil flow, helping the outboard run smoother and respond faster when you throttle up. The spark plugs provide strong, consistent ignition you can feel in every shift and every acceleration. And replacing the impeller — something many boaters forget until it’s too late — ensures your cooling system stays strong, steady, and dependable.

The kit also includes fresh anodes to help protect critical metal components, especially if you spend any time in brackish or saltwater. The thermostat and seals tighten everything back up, giving you that “secure” feeling when the engine reaches its operating temperature and stays there without drifting.

What makes this kit truly practical is the simplicity. Everything you need is in the box — you don’t have to hunt down part numbers, guess which filter your serial range uses, or worry about missing pieces. It’s a streamlined way to take care of your engine yourself or provide your technician with exactly what they need.

Why Buy OEM

Maintenance is only as good as the parts you use. With genuine Mercury Marine components, you’re installing parts engineered specifically for your outboard — not something generic that “should fit.” OEM filters trap finer particles, OEM impellers last longer under heat and load, and OEM anodes protect the metal your engine depends on. Over time, that adds up to fewer breakdowns, better fuel economy, and a motor that feels tight and confident every time you start it. When you’re doing a major service interval like this one, using the real thing just makes sense.

FAQ

Q1: Which engines does the 8M0090559 Maintenance Kit fit?

It fits Mercury 40–60 horsepower FourStroke EFI outboards with BigFoot or Command Thrust gearcases, serial number 1C000001 and newer.

Q2: What makes this kit better than buying parts individually?

Everything is OEM, perfectly matched to your engine, and bundled so you don’t miss any critical service components.

Q3: How do I know if this is the right kit for my engine?

Check your serial number and verify that your outboard is a 40-60HP FourStroke EFI with BigFoot or Command Thrust gearing.

Q4: Can this kit be used in both saltwater and freshwater setups?

Yes — all components are built to withstand corrosion and moisture common to both environments.

Q5: Is installation straightforward?

Most experienced boaters or trained technicians can complete the service easily with standard tools and your owner’s manual.