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Hello. Here is the general procedure you can use to winterisize. Note that this procedure does not require that you use drain plugs at all (which avoids the issues of finding them, corrosion, etc.) - this is the process that most shops will use.
1. Fill your fuel tank to minimize condensation and add the appropriate amount of a good fuel stabilizer like Stabil - be sure it's for ethanol if your gas contains ethanol. Change your fuel filter if it hasn't been changed recently. Do this first so when you run the engine the stabilizer will get into the entire fuel system.
2. If you have a closed cooling system, drain it and replace with a 50% mixture of water and antifreeze. Don't use more than 50% antifreeze, since this will decrease the ability of the system to cool the motor. My suggestion is to mix your own and not to buy the pre-mix - mixing your own is a lot cheaper.
3. Warm up the engine so the thermostat is open (be sure to provide cooling water). Disconnect the engine suction hose from the raw water intake. Place the end of the disconnected hose into a container of non-toxic antifreeze (the "pink stuff"). Now start the engine and let it run a few seconds until antifreeze comes out the exhaust. Alternately, you can use "bunny ears" and rig a hose to a container of antifreeze to accomplish the same thing. You can actually buy a kit for this at marine stores like West Marine or Boaters World (here is a link:
4. Optionally use fogging oil to help coat the interior of the engine, but only do this if you have a carbureted engine - the fogging oil will foul the sensors in an EFI motor. If used, spray it into the air intake just as the antifreeze starts to appear at the exhaust in the previous step 3. This should stall the engine, otherwise shut it off. Some owners also remove the spark plugs and spray fogging oil into each cylinder, then replace the plugs.
5. While the engine is warm (not hot), change the engine oil and filter. If you leave old oil in the motor, the contaminants will tend to corrode the internal parts while in storage.
6. Spray a light coating of WD-40 (or similar) on the alternator and starter motor. Try to avoid getting the spray on the belts. Also spray linkages and cables.
7. Cover your air inlets, breathers, exhaust and fuel tank vents.
8. If you have a fresh water system, livewell, etc. run all the water out of the system, then disconnect the inbound hoses to the pumps, run a hose from the pump to a container of non-toxic antifreeze, then turn the pump on until antifreeze run out. Don't forget to replace any lines you removed. For the fresh water system, the antifreeze can be added directly to the water tank. Be sure to drain and bypass the hot water heater if you have one, otherwise you'll need 6 gallons of antifreeze just for that.
9. Remove the batteries and store them in a protected warm area, such as a garage or basement. This is a good time to check the water levels if they are wet cell type and fill them with distilled water if low. Don't worry about charging them now, but put them on a charger a week or two before you are ready to go in the spring.ing either a hydrometer or an open circuit voltage test (12.6 volts or higher).
10. Drain and replace the gear oil from your outdrive. Be sure to fill from the bottom until oil comes out the top hole so there are no air pockets.
11. Grease any grease fittings on the outdrive. Cover the prop and shaft so water doesn't get into the shaft area.
12. Some owners remove the props and send them out for reconditioning if necessary. You should at least carefully examin the prop(s) for damage and remove any foreign material from the prop, hub, etc.