I am taking delivery of a new Beneteau 41 this week in Annapolis and would like to keep sailing until Thanks Giving and fully winterize after that. Although winter takes usually until January to really set in here, there is always a possibility to get a couple chilling nights here and there and I am trying to find a way to prevent freezing damage if this should occur. My boats will be docked in a nice marina with dock power. Can I possibly leave a small ceramic heater on to maintain enough warmth in the boat? My A/C system can also heat but am not sure I can leave it on 24/7. Any thoughts?
I would simply monitor forecasts closely between now and when you expect to stop sailing. Monitor air and water temperatures where you keep the boat.
As air temperatures approach freezing, I'd begin winterizing the fresh water systems. At that point, I might put 1 or 2, 100 watt drop-lights in the engine compartment. They are safer than a forced air heater, yet still provide surprising warmth. Plenty for an engine.
As water temperatures finally approach 30F-32F, I'd winterize the engine and be done for the season. I realize that Chesapeake water is brackish, but depending on what creek you're docked in, the salinity may lean towards the fresh end of things, so the freezing temperature will be higher than pure ocean brine.
As far as heaters go, I agree with those who say that if your wiring is sound, and of the proper capacity, and your heater is in good condition, then you're about as safe as you're going to get.
I installed my shore power system. I used the proper components for marine wiring and I check everything regularly. I also check if the heater's power cord is getting hot, as was suggested previously.
I use the oil filled, electric radiator heater. They are safer and draw slightly less amps than a forced-air ceramic heater because the element is always submerged in oil. The radiators are the heater of choice for liveaboards in my marina. Last night, our temps were down to 48F. I set my radiator to the 300 watt setting and perfectly comfortable while sleeping.