Curious. It is a 2 or 4 stroke?
The crankcase full of oil (like your car) adds a factor or two. But for sitting idle, all of the above is good advice.
We keep a twin O/B tow boat in all year. Unless the upper part of the Shrewsbury ( buoy#5) ices up.
Other issues to do with through hulls, bilge pumps, etc. Anything with water in it, when it gets cold enough, will freeze, expand and possibly break what contains it. Very bad for a through hull when a hose above it freezes, pops, and then thaws. You go to the bottom.
