Nothing I run mine during the winter and I don't do any thing different. If boat is left outside in freezing temp and rain you may want to get all the water out of the exhaust port by letting the motor all the way down and leaving it like that. If you have leaking seals on the prop shaft it will fill with water and could freeze but usually the lower unit will burn up. Check lower unit for water if it has water in it it will be cloudy looking.