Newby-Winterizing question

Hello,

I recently bought a 1972 bass boat with a '72 50 HP mercury outboard.

I was told all I need to do to winterize it is drain the water layer in the lower unit and replace the drainage with oil. Is this true, or do I need to acutally put the ear muffs on and flush everything out?

Any advice would be good. I live near a lake on a power plant which I was told by the marina never freezes and some people take their boats out all year long (I live in central IL). This is why I don't want to completely winterize it if possible, because if we get some warm winter weather I would like to take it out.

The boat is stored in a garage. It is not a heated garage, but the garage is connected to the house.

Thanks

 

Here is the winterizing procedure I use on my outboard, and those of friends. (One of which is a '79 Johnson that has been to the shop exactly once in its lifetime. And with it, we skip the flush, being on a freshwater lake with no garden hose to speak of.)

Before final trip of season: Add 6-month fuel stabilizer to gas tank.
Before storage, with engine out of water:
1) Connect flush fitting (earmuffs)
2) With garden hose on full pressure to flush fitting, remove cowling and start engine (not strictly necessary, but it's good for the water pump and coolant passages to get a freshwater flush now and then to clean out any built-up debris).
3) After ~1 minute of steady cooling water flow from all normal outlets, disconnect fuel line with engine still running. (This drops the fuel level in the carb, seems to help prevent fuel varnish from forming in the lines.)
4) At first sign that engine is about to stall, begin spraying fogging oil into carb intake. Press kill switch after a few seconds of fogging. (This ensures that the crank, rods, reed valves, etc. are thoroughly coated in fogging oil.)
5) Disconnect all electrics, kill switch, etc.
6) Drain lower unit gear oil
7) Remove spark plugs, clean, spray some fogging oil in cylinders, and reinstall plugs (but not plug wires).
8) Refill lower gear oil by squeezing oil up from bottom hole. (Never, ever leave it with the lower gearcase empty!)

A little more elaborate than some, perhaps, but even so, it takes less than half an hour.

All that's left to do in the spring is reconnect the spark plug leads, and it fires right up (albeit with some smoke for a minute, thanks to the fogging oil).

If you're going to use the thing regularly throughout the winter, that's OK. Just skip the fogging oil (it's essentially a storage lube to prevent corrosion). But it is absolutely essential that you ensure ALL water is drained from the thing before it is subjected to sub-freezing temperatures in storage.