I don't have any current experience with outboards, so I'll assume they are different. With stern drives, from what I've heard for everyone, is that fogging gives your engine a layer of protection that "might" be needed. Rust and other corrosion can form if this layer is not provided.
It doesn't mean it will happen, but it could happen, and it's a very expensive fix if it does happen.
http://www.boattest.com/Resources/vi...px?NewsID=3884
Still irritates me that my dealer, once again, stored my drive in the Up position
I hate it when I have to clean or replace plugs. But the alternatives are much worse if my luck ran out.