Point ! Counter Point ! I to live in Mich and follow the mfgs recommendation to add fuel stabill, It can't hurt. As for fuel level. I store my big boat aproxx 1/3 full. If I stored at 90 % of capacity (270 gall) that would equal 1,647 lbs of dead weight. My feeling is if I do have any water in the spring my fuel/water filters will catch it. From what I have heard it's when you have rapid swings in temp that you get moisture build up and expansion. After many years wintering this way I have yet yet to have a problem. Just my two cents.

SLP

Adding Isopropyl Alcohol (Dry Gas) to your fuel system is beneficial. It holds water in suspension, allowing it to be burned in the combustion process. 12 ounces to 16 gallons is common.
This is a periodic treatment, not something you would add at every fill up. I would do an application in the spring for your first outting. For you guys that are Octane Sensitive (High Compression and Supercharged), run that first tank out at cruise rpm. Your fuel has lost some of its octane rating over the winter months, even if it was stabilized. This info was passed on to me by one of our renowned fuel system experts.

I remember reading an article put out by one of the major oil companies regarding the use of fuel stabilizer. Basically, the gas won't go "bad" (ie loose the aromatics) for about 11 or so months. In other words, the gas won't go bad over winter. What I think is the greater problem is that the gas evaporates out of the fuel bowl leaving all the deposits behind.

Cord, You are right on.
The stabilizer prevents the oxidation of the fuel. Meaning that the stabilizer surrounds the fuel molecules with a coating so that oxygen will not breakdown the molecules in to the gummy stuff we don't want in our fuel system.

The big mystery do I add stabelize or dry gas?
Question ! Where do you buy your gas at a marina or a gas station?
Marina's seem to sell water enriched fuel, that is why we all run the water seperators, simple but reality.
Do I add stabelizer?
Seems the typical answer can' t hurt.
What is reality?
The fuel of today is not the same as fuel as ten years ago.
I have heard that fire departments drain their fuel out of their life support systems every two months or so to guarantee they are ready to roll when they are called upon.
My opinion which is like and a-----e everyone has one.
Run the tank you have dry when you put the boat in and put in fresh fuel, with some fuel injection cleaner and you are ready to roll.
Have a good day Brian

Stabil or similar will keep your fuel burnable but it doesnt stop it from evaporating. The fuel in your float bowls will evaporate if left for a long time. When this happens it will leave a varnish behind. When I winterize, I treat the tank and then run the motor. I then kill the fuel pump and hit the carb with fog oil as it runs out of fuel. Less varnish in the carb that way.