Anit freeze
This is probably the only thru hull you can't run anti freeze down. As soon as you disconnect the hose the pressure from the packing gland will push water back up thru the nipple. So no matter how you go about it water always seems to get into that hose. That's why I wrap it with insulation. Not sure it does any good but it gives me some little piece of mind. I also block the bilge blower tubes with rags to keep air out. Just remember you have them there in the spring when you fire the engine back up. For the other thru hulls I run the pink anti freeze down all of them or pull the hose and dry the inside of the thru hull. So far so good. As for the space heater, most marinas either don't allow them or discourage their use. We use the ceramic type with the tip over protection, leave it set on low and on top of a hot plate on top of the oven. Power boater friends also leave a work lamp on in the bilges. These are the high wattage shielded lamp types and work very well without risking an explosion.
This is probably the only thru hull you can't run anti freeze down. As soon as you disconnect the hose the pressure from the packing gland will push water back up thru the nipple. So no matter how you go about it water always seems to get into that hose. That's why I wrap it with insulation. Not sure it does any good but it gives me some little piece of mind. I also block the bilge blower tubes with rags to keep air out. Just remember you have them there in the spring when you fire the engine back up. For the other thru hulls I run the pink anti freeze down all of them or pull the hose and dry the inside of the thru hull. So far so good. As for the space heater, most marinas either don't allow them or discourage their use. We use the ceramic type with the tip over protection, leave it set on low and on top of a hot plate on top of the oven. Power boater friends also leave a work lamp on in the bilges. These are the high wattage shielded lamp types and work very well without risking an explosion.