How to Winterize a Mercruiser 3.0

by Jared Curtis

speed boat image by sheldon gardner from Fotolia.com

Before putting your boat away for the winter, you must first winterize the motor. Your Mercruiser 3.0 uses the water in the lake to cool the engine while boating. This water stays inside the engine. Failure to remove the water will cause freezing. As the water freezes, it expands. This will cause the engine block to crack. A cracked block is an expensive repair that can be avoided by spending a small amount of time before winter.

Step 1

Determine the amount of fuel you have stored in your tank by turning the key to the accessory position. Do not start your engine.

Step 2

Pour the proper amount of fuel stabilizer into the fuel tank by referring to the chart on the bottle.

Step 3

Remove the drain plug with a 9/16-inch wrench. The drain plug is at the bottom rear of the boat.

Step 4

Open the engine compartment and remove the nut that secures the spark arrester to the carburetor with a wrench. The spark arrester is a round metal air filter.

Step 5

Attach the garden hose to the out-drive earmuffs. The earmuffs slide onto the out drive directly over the water vents. Make sure the muffs are properly placed and covering each vent.

Step 6

Turn the water source on. Allow the air pockets to exit the hose.

Step 7

Turn on the blower switch, which is located on the dashboard. Let it run for five minutes.

Step 8

Start the engine by turning the key. Let the engine idle for at least 10 minutes to allow the stabilized fuel to reach the carburetor.

Step 9

Locate the fuel shutoff switch on the gas line that enters the carburetor. If no switch is present, pinch the fuel line with your hand. Quickly spray fogging oil into the carburetor. Open the flaps and spray directly into the carburetor until the engine dies. This will keep the floats from gumming up during storage.

Step 10

Remove the drain plugs on the engine block to release the water with a wrench. Refer to the owner's manual inside the glove box for proper drain plug locations. Allow the water to fully drain from the engine before reinstalling the plugs.

Step 11

Lower the out drive by pressing the button on the throttle assembly. Have someone watch the out drive so that it does not hit the ground. This will keep the gears lubricated in the out drive throughout storage.