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Mercury | 300 Hour Service Kit | 8M0113483

Stay on schedule with a complete 300 hour service kit designed for Mercury 40, 50, and 60 HP four-stroke outboards equipped with standard gearcases. Built around 25W-40 synthetic blend four-stroke oil, this kit combines routine oil-change and gearcase service items with the additional wear parts commonly addressed at the 300 hour interval—fuel system filtration, cooling components, ignition parts, and corrosion protection. It is a simple way to refresh critical systems, reduce downtime, and keep your outboard running reliably for the next season of use.

Application: Mercury 40/50/60 HP Four-Stroke – Standard Gearcases Only

What’s Included in This Kit

• 1x 25W-40 Synthetic Blend Four-Stroke Engine Oil (Gallon)
• 1x Gear Lube (Quart)
• 1x Oil Filter
• 1x Low Pressure Fuel Filter
• 1x High Pressure Fuel Filter
• 1x Oil Drain Seal
• 2x Gearcase Drain Seals
• 1x Thermostat
• Thermostat Gaskets (Included)
• 4x Spark Plugs
• 1x Water Impeller Repair Kit
• 1x Power Trim Anode
• 1x Lower Unit Anode

Why This 300 Hour Service Kit Matters

• Milestone service coverage: Goes beyond basic fluids to address cooling, ignition, and fuel filtration wear items.
• Cooling system refresh: Thermostat and impeller components help support stable operating temperatures and reliable water flow.
• Fuel-side protection: Fresh low and high pressure fuel filters help reduce debris before it reaches sensitive fuel system components.
• Corrosion defense: Includes trim and lower unit anodes to help reduce galvanic corrosion in harsh marine conditions.

FAQ

Does this kit fit Command Thrust or other specialty gearcases?
No. This kit is intended for standard gearcases only.

Why are there 2 gearcase drain seals included?
Many gearcases use sealing washers at both the drain and vent screws, so replacing them together helps support a proper seal.

Why replace both fuel filters at 300 hours?
Fuel filters can load up over time. Replacing both helps support consistent fuel pressure, smooth running, and dependable starting.

What should I confirm before ordering?
Verify your engine is a Mercury 40/50/60 HP four-stroke with a standard gearcase.

• Engine Application
  • 40 HP EFI 4 CYL - 1C453840 & Up
  • 40 HP EFI Jet 4 CYL - 1C453840 & Up
  • 40 HP EFI SeaPro 4 CYL - 1C453840 & Up
  • 50 HP EFI 4 CYL - 1C453840 & Up
  • 35 HP EFI Jet 4 CYL - 1C453840 & Up
  • 60 HP EFI 4 CYL - 1C453840 & Up
  • 60 HP EFI SeaPro 4 CYL - 1C453840 & Up