Winterizing an Inboard/Outboard Engine

This winterizing procedure can be modified to meet the specific needs of your engine. Much of this is contained the operators manual on the boat if you have it. I am sure there are other ways of doing this, but I have never had any problems with my engine after 14 years of following this procedure.

Add a fuel stabilizer to the fuel tank so that it gets into all the fuel lines and carburetor when you start the engine. Stabilizer is available at most marine outlet stores. Fill the fuel tank at least ¾ full to cut down on condensation. I have filled my tank full, only to have it come out the overflow when the boat gets warm in the spring from the sun. Using a flushing attachment on the garden hose warm the engine up. Run the engine until the temperature gauge reads in the normal range. With the engine warm, change the oil and oil filter. I don’t like my engine to sit over the winter months with used oil in it. A trick I learned to prevent oil from being spilled in the bilge is to us a heavy duty plastic bag, about one gallon in size to catch the oil filter when it is removed from the engine. Install a new filter and add the correct amount of oil. Start the engine and check for leaks at the filter. After the oil change, I fog the engine using a fogging oil available at most marine outlets. Remove the carburetor flame arrestor and spray the fogging oil down the throat of the carb with the engine idling at about 1200-1500 RPM. You spray it in the carburetor while the engine is running until you almost kill the engine, and thick white smoke is coming out the exhaust. Turn off the key while the engine is still running rough from the fogging oil. This coats the cylinder walls, valves guides, intake manifold, and exhaust manifold with a protective coat of oil. Depending upon my mood, I may also remove the spark plugs and squirt some of the fogging oil in the cylinders. If I do this I disconnect the coil so I can crank the engine without it starting to distribute the oil on the cylinder walls.

My boat has a salt water cooling chamber for the power steering. It’s a pain to get to the drain bolt on this so I use an air compressor to blow the water out of this chamber and out the water intake. I disconnect the hose that goes from this chamber to the engine and connect the air supply up on the engine end of the hose. I remove the drain plug(s) on the block and manifold(s) and drain all water. Make sure the drain plug is out of the boat so the engine coolant does not collect in the bilge. Put the drain plug(s) back in the block and manifold(s). Remove the hoses from the thermostat housing and pour a total of about 2 quarts of RV antifreeze into the block, mainfold(s), and any other water lines. (RV type in non-toxic) If I suspect any water is anywhere in the lines I blow some air through them with the antifreeze in the lines, then pour a little more antifreeze in when finished. I don’t fill the block with antifreeze, but put enough in to counter any water that may be in low lying areas, about two quarts. I pour this into the block through one of the hoses I have disconnected from the water pump. I remove the batteries and all other accessories and gear and store it in the basement/garage. I have dual batteries and a dual charger that I made. Because of the various wires attached to the batteries, I connect the wires that came off of each battery terminal together using a nylon tiewrap. This helps me in the spring when I have to re-connect these wires. I spray the entire engine down with WD-40 to protect it from rust. This is a must as condensation will form on the engine when it is cold and the sun warms the boat. If you cover the boat make sure there are some breathing places in the cover if you shrink-wrap it. Store the boat with the outdrive down so water does not collect in it. I check the oil level in my outdrive. As long as the level is where it should be, I assume that no water has entered the drive and mixed with the oil which would change the oil level. If you suspect there is water in the oil, the outdrive seals should be replaced and fresh oil added. The maunal says to change the oil in the outdrive each season, in the fall. I jack up the trailer and set it on blocks to get the tires off the dirt. You should remove the trailer wheels and clean and then repack the wheel bearings. This is best done in the fall but somehow I always end up doing it in the spring. Remove the drain plug from the boat in case rain water gets into the boat over the winter. Store the plug where you’ll be sure to see it in the spring so it can be installed before launching your boat. Again if I’m in the mood, I wax the boat and all metal fittings. I charge the batteries about once per month during storage. In the spring, I install the batteries, and since all hoses are connected to the engine, I hook up the flushing attachment and fire her up. After running one tank of gas through the engine, I change the fuel filter and then give the engine a tune-up.

This is what I have done for the 14 years I have had my boat. My son works in the marine industry and use to help me. It takes me about 2-3 hours to do this. My engine looks like it is only 1-2 years old.

Hope the has been of help to you. Email me if you have any questions. May your engine always start, and your lines be tight with big fish!

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