Time to winterize your block with plumbing antifreeze.
After allowing the motor to run for 5 to 10 minutes, per the previous step’s instructions, shut it off and disconnect the garden hose. Hook up the flushing muffs to a winterizing kit and fill the kit with WinterProof™ Marine Water System Antifreeze.
Remove the cowling to gain access to your boat’s air intakes located at the front of the engine. Open the valve to the winterizing kit and restart your motor and allow the antifreeze solution to drain into the tank. You’ll start to see the antifreeze discharging via the water that exits the motor.
While the engine is running. spray fogging oil into the carburetor(s). You may notice lower horsepower engines stall, and higher horsepower engines will cough and sputter – this is normal. Continue running the motor while spraying a decent amount of fogging oil through the intake. Discontinue the fuel line from the engine and continue to spray fogging oil into the engine until it dies. Doing this will prevent varnish deposits from building up while inactive during the winter.
If your boat has an Electronic Fuel Ignition (EFI), you need to follow a slightly different procedure for fogging. First, ensure that you’re using a fogging solution formulated for EFI motors.
Rather than fogging the cylinders, put a small amount of stabilized gasoline in a container and mix in a fogging oil formulated for EFI motors. Run a fuel line from the container to the motor and run the motor until you see white smoke exiting the exhaust. Before the winterizing kit runs dry, turn off the motor. Do not run the motor until it dies from lack of fuel as this can damage the fuel system.