How to Winterize the Inboard of a Mercruiser
- 1). Unclasp the engine cowl clips and remove the engine cowl from the engine. Place a drain pan under the oil drain plug, and use a socket to remove the drain plug. Use an oil filter wrench to remove the oil filter. Place a new oil filter on the engine and tighten it by hand. Screw the oil drain plug back into the pan and tighten it with a socket. Pour in the prescribed amount of new oil into the crankcase -- refer to owner's manual.
- 2). Refer to your owner's manual for the location of the coolant drain plugs on the engine and exhaust manifold. Loosen each petcock valve (or bolt) with pliers or a socket and drain the coolant into a drain pan. Re-tighten all of the petcock valves and plugs with pliers or a socket. Replace the coolant with a mixture of half water and half glycol (coolant), filling the system to the top mark.
- 3). Loosen and remove the outdrive gear oil plug with a socket and let the old gear oil drain into a pan. Replace and tighten the plug with a socket. Loosen and remove the gear oil filler cap with a socket. Pour the prescribed amount of new gear oil into the outdrive crankcase. Replace the filler cap and tighten it with a socket.
- 4). Fill the fuel tank to the top. Make sure you submerge the stern drive unit in water. Take a can of fuel stabilizer and add it to the gas tank. Start the engine and let it run for at least 15 minutes to let the stabilizer chemically react with the fuel and fill the carburetor float bowl. Shut the engine off.
- 5). Pour about 1/2 pint of gasoline into a coffee can. Disconnect the main inlet fuel line to the carburetor. Place the fuel line in the coffee can and keep it stable and away from any sparks from the engine. Remove the spark arrestor on the top of the engine intake with a socket. Have an assistant start the engine. Spray engine fogger into the intake port, just enough to keep the engine running. When the gasoline just begins to disappear from the bottom of the coffee can, flood the intake port with fogger and let the engine die. Replace the flame arrestor and tighten it with a socket.
- 6). Use pliers to loosen the fuel separator bowl from the filter housing. Dump out the contents into a drain pan. Place the bowl up into its seat and tighten the valve screw with pliers. Use a screwdriver to loosen the hose clamps to the fuel filter, and pull the old fuel filter off. Hook up the fuel line hoses to the nipples on a new fuel filter and tighten the hose clamps with a screwdriver.
- 7). Use your fingers to grease the stern drive gimbal bearing and the engine mounting coupler. Inspect the steering cables for tautness and alignment. Check the engine belts for tightness and condition. Grease the steering rod joints and the swivel joints on the trim arms. Spray the entire engine with a can of rust inhibitor, applying a thin, even coat to all metal surfaces. Disconnect the battery cables with a socket. Store the battery in a safe place, but charge it to maximum before storing. Remove the bilge drain plug to allow for drainage.
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