No need to trickle charge them over the winter though. I never blow my water system hoses out. Running anti-freeze through them works fine. It gets a lot colder here in Maine than it ever does in Annapolis.

You can probably do the entire system with 12 gallons of anti-freeze. It normnally takes me about an hour to do my boat but I don't have AC or a generator and I only have one head. So figure 2-3 hours for your boat not including oil changes.