Cfiegehen,
I live on my boat. I have live on it during some very snowy winters in Baltimore. Here is what I have learned:
1. Humidity is a significant factor while on board. Since boats are not well insulated, condensation is the real problem. To help control condensation (which normally will form on surfaces with little to no insulation such as windows, windshields, etc.) try to insulate the windshield with some type of thin bubble type insulation or a shrinkable clear film type for the windows. I cover my large front windshield (on the outside) with a cover I made out of the silver bubble type insulation that they sell in Home Desperate. It comes in a roll and is easily cut to fit. It provides just enough of a hard cold barrier to prevent the condensation from forming on the inside. The shrinkable clear film for the side windows works well also.
2. The only way to "dry" the air is through heating or a condensing dehumidifier. Marine suppliers do sell air dryers that operate on very low power and move large amounts of air. Typical dehumidifiers will work also albeit they can be big and noisy.
3. The single BIGGEST issue you will face is power availability. What I mean is the amount of power available to you while on board. Most boats have either a dual 30 amp or single 50 amp connection. With that said you only have half of that available to power the AC side of your boat...usually the other half is for the AC. 30 amps of 110V is next to nothing power wise. Two 1500 watt heaters will eat up 30 amps alone. On top of that you still need power to run your fridge, hot water heater (another high draw load), dehumidifier, battery charger, some lights, etc. So as you can see, the likely hood of powering everything you need is very limited and requires jockeying around the power load as needed.
This is how I do it:
1. Insulate as much as you can. This will help mitigate the moisture problems on surfaces.
2. I use a indoor safe propane ceramic IR heater. It cranks out the heat and can warm the boat quickly.
3. Use small temperature controlled safety heaters in the cabin to keep the interior above freezing when you are not on board. Keep the cabinet doors open to prevent pipes and drains from freezing. If this doesn't work well then winterize everything and go with bottled water.
4. Winterize the engines and all other water systems below deck (AC, etc.) and close off the engine vents.
5. Wire in two additional outlets from the AC side of your electric. This will allow you to run additional heaters and/or shift the power load as needed.
Good luck. I will be with you in spirit this year as well.
