Since no one else has chimed in, I will tell you what I do. You want to do several things:
1. Flush the cooling system. You can do this the fancy way but buying the "rabbit ears" flushing adapter from your favorite marine store or the simple way which is to put the engine into a bucket filled with fresh water and run it for a little while. If you flush with fresh water you will need to keep the engine somewhere where the water wont freeze.
2.
Fuel system. Honestly, all I do is run the engine without the
fuel line attached until it is all out of
fuel. In the past I have fogged the engine using a fogging spray thru the air inlet or added a
fuel stabilizer to the
fuel.
3. I would change the spark plugs in the spring and not know. Its also a good time to change the
fuel filter and the zincs. No sure if your engine is 2 cycle or 4; if its 4 you will want to change the engine oil as well.
4. Changing the lower unit oil (gear lube). Goto the marine store and get a tube of gear lube that is appropriate for your engine. It is easier to change the gear lube if you run the engine for a while first as warm gear lube will flow more easily. Stand your engine upright. There shud be 2 screws one a couple of inches above the other. This is kinda a messy operation so make sure you have something under your engine to catch the lube. Generally you can take out the bottom screw first the the lube will not gush out. Once you take out the upper screw, it shud really flow out. Let it drip out for a good 20 mins or more to make sure you get all of it out. The gear lube that you bought shud have a long, narrow tube at the end. Cut the top off this tube and jam the it into the lower screw hole. Keep squeezing the tube until the lube starts to ooze out of the top hole. Once this happens, put the screw back into the top hole. Remove the tube of gear lube and quickly replace the lower screw. It helps to have a helper when you do this. Good Luck.
HAM