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Mercury | 300 Hour Service Kit | 15/20 HP | 8M0120838

The Mercury 300 Hour Service Kit – 8M0120838 provides the key maintenance components needed to properly service Mercury 15 HP and 20 HP four-stroke outboards with serial numbers 0R235949 through 0R833819. Designed to simplify scheduled maintenance, this kit includes the oils, filters, cooling system components, ignition parts, and seals required for the 300-hour service interval.

Performing routine maintenance at recommended service intervals helps protect internal engine components, maintain proper cooling system function, and ensure reliable performance on the water. This kit packages everything needed to refresh the lubrication system, replace common wear items, and maintain efficient engine operation.

What’s Included in This Kit

• 2 x Quarts 25W-40 Engine Oil
• 1 x Quart Gear Lube
• 1 x Oil Filter
• 1 x Fuel Filter
• 1 x Oil Drain Seal
• 3 x Gearcase Drain Seals
• 1 x Thermostat
• 1 x Thermostat Gasket
• 2 x Spark Plugs
• 1 x Water Pump Impeller Kit
• 1 x Anode

Why Perform the 300 Hour Service?

• Maintain proper lubrication with fresh engine oil to reduce internal wear.
• Protect the gearcase with new gear lube and drain seals.
• Ensure proper cooling with a new thermostat and water pump impeller.
• Improve ignition performance with fresh spark plugs.
• Reduce corrosion by replacing the sacrificial anode.

Engine Compatibility

• Mercury 15 HP Four-Stroke Outboards
• Mercury 20 HP Four-Stroke Outboards
• Serial Numbers 0R235949 – 0R833819

Always confirm your Mercury outboard serial number before ordering to ensure proper compatibility.

• Engine Application
  • 15 HP Carb 2 CYL - 0R235949-0R833819
  • 15 HP Carb 2 CYL JCI - 0R558208-0R833819
  • 20 HP Carb 2 CYL - 0R235168-0R833819
  • 10 HP Carb 2 CYL - 0R575531-0R833819