As long as there's no water in the cooling system
you shouldn't have any problem leaving it on land...

if you leave it in the water near baby island the coolant will be salt water which has a freezing point substantially below 32F and it takes a lot more than a few hours of 12 degree weather to freeze salt water even if it's in the cooling system as the boat is parked out of the water, but if the boat's in the water the entire bay would need to freeze before you would have problems and that isn't going to happen this weekend........

on the other hand I can remember a picture from my youth of an adult "great white hunter" as he walked back over an ice covered skagit bay with a brace of snow geese he had snuck up on and terminated.........

but that kind of opportunity requires multiple days in the near zero or below zero range.....


so, as much as we all might feel an urge to blame the impending cold spell on "global warming", this kind of thing has happened before....

note: I'm assuming your boat has a conventional 2 or 4 stroke outboard motor....