How Do You Winterize a Mercruiser Engine?

How Do You Winterize a Mercruiser Engine?

Winterizing a Mercruiser boat requires fixing any mechanical problems and flushing the system with fresh water. Once the system is clean, fog it and add a fuel stabilizer to prevent the small parts from freezing, which may cause irreparable damage.

Always remember to disconnect and remove the battery before beginning the winterizing process.

  1. Drain the cooling system
  2. Completely drain the cooling system of any water. Be sure there is no water left in the exhaust manifolds, hoses or block. Remove the water hoses that go to the block and manifolds and add antifreeze until it runs out of the petcocks

  3. Fog the system
  4. Fogging the system requires a 20-weight oil or engine fogging oil. Pour this oil into the throat of the carburetor with the engine running at a fast idle.

  5. Add a fuel stabilizer
  6. Add a fuel stabilizer to the boat's fuel tank. This will prevent the fuel from becoming thick and gummy over the winter. Take this opportunity to change the fuel filter.

  7. Change the drive gear lubricant
  8. Change the drive gear lubricant to ensure there is no water in the lower unit. Remove the outdrive and grease the universal joint. Replace the gimbal bearing if it shows signs of wear.

  9. Check the prop and speedometer ports
  10. Probe the speedometer and cooling ports with a fine wire to remove any water that is trapped inside. Check the prop and have it refinished if necessary.

  11. Coat the electrical system
  12. Spray a fine mist of silicone spray on the electrical system and engine block.