How to winterize a mercruiser 5.0 mpi

Written by jared curtis
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How to winterize a mercruiser 5.0 mpi
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Your MerCruiser 5.0 MPI must be winterised to protect the engine during cold weather. Water is sucked from the lake by the impeller inside the outdrive, and is used to keep the engine cool. This water stays inside the engine, and does not drain automatically. Frozen water can cause the engine block to crack and also can corrode the metal. You can avoid costly repairs by properly winterising your boat in the fall.

Skill level:

Things you need

  • Fuel stabiliser
  • Wrench set
  • Outdrive muffs
  • Garden hose and water source
  • Fogging oil

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  1. 1

    Pour the appropriate amount of fuel stabiliser into the fuel tank. Refer to the label on the can for the correct mixture.

  2. 2

    Remove the boat drain plug at the back of the boat with a wrench. This will allow the water remaining in the engine to flow out of the boat when you drain the engine.

  3. 3

    Open the engine compartment cover. Remove the spark arrester from the carburettor, using a wrench. The spark arrester is a round air filter that mounts on top of the carburettor.

  4. 4

    Attach the outdrive muffs to a garden hose. Slide the muffs onto the outdrive. They should cover the vents on each side of the outdrive.

  5. 5

    Turn the water on, and allow the air pockets to flow through the hose.

  6. 6

    Turn the blower on, and allow it to run for five minutes. The switch for the blower is on the dash.

  7. 7

    Start the engine, and allow it to idle for 15 minutes. This will allow the stabiliser fuel to reach the carburettor.

  8. 8

    Fog the engine by spraying fogging oil into the carburettor until the engine dies.

  9. 9

    Turn the water off, and remove the outdrive muffs.

  10. 10

    Reinstall the spark arrester.

  11. 11

    Remove the drain plugs from the engine block with a wrench. Refer to your owners manual for drain plug locations, as each year model is different. Allow the water to drain from the engine before you reinstall the drain plugs.

  12. 12

    Lower the outdrive by pressing the trim button on the throttle. This will keep the gears lubricated during storage.

  13. 13

    Turn the battery switch to the "off" position.

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