How to Winterize a Four Stroke Yamaha Outboard Motor

Written by will charpentier
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How to Winterize a Four Stroke Yamaha Outboard Motor
The Yamaha warranty favours the dealer for winter preparation. (toy outboard motor image by pearlguy from

The Yamaha Motor Corporation makes motorcycles, all-terrain vehicles, utility vehicles, portable generators, boats, the Waverunner personal watercraft, and outboard motors. Yamaha's maintenance guidelines are based on "hours of operation" rather than a seasonal preparation, and there are restrictions on how much the owner can do to prepare the motor for its winter layup. The motor's self-draining seawater cooling system eliminates a significant part of the winter storage process.

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Things you need

  • Fuel stabiliser
  • Fogging oil
  • Gear case lubricant
  • Heavy marine grease

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  1. 1

    Put a container of fuel stabiliser in your fuel tank before you take the boat out for the season's last outing. Before you trailer your boat at the end of the day, fill your fuel tank one last time and add another container of fuel stabiliser to the tank.

  2. 2

    When you pull your boat to the trailer, hook the trailer winch cable to the bow of the boat. Before you shut the motor down, remove the motor cover. Remove the air cleaner and flame arrester from the carburettor, and turn the fuel supply valve to the "Off" position.

  3. 3

    Spray fogging oil into the carburettor until the motor chokes off. Pull the boat up onto the trailer and pull the boat into the boat launch parking area.

  4. 4

    Remove the spark plugs from the motor, one at a time, and spray fogging oil into the spark plug holes. Replace the plugs, remove the kill switch to keep the motor from starting and use the starter to "turn the motor over" two or three times, to distribute the fogging oil in the cylinders.

  5. 5

    Unscrew the vent plug on the lower unit and the gear case drain plug on the bottom of the gear case to drain the gear case lubricant into an oil drain pan. Replace the vent screw, refill the gear case with new gear lubricant--through the drain plug hole--and replace the drain screw.

  6. 6

    Grease the swivel bracket for the steering system, steering tube and tilt mechanism on the tilt and trim system with heavy marine grease, and cover the grease nipples with grease. Grease the cowling latches and spray the power head with a penetrating spray lubricant.

  7. 7

    Replace any external zinc anodes on the engine that have eroded to 1/2 their original size. Touch up the paint on the cowling and cover and allow the paint to dry thoroughly. Wax the entire outboard.

Tips and warnings

  • When in doubt, follow the recommendations of the service manual for your specific Yamaha 4-stroke engine model.
  • While your engine is under warranty, allow your dealer to complete the "refer to dealer" steps in preparing your boat for winter storage, to keep your warranty in force.

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