Hi Grant,
I'm looking at the same situation as you just a few short miles south of you in Lake Stevens, WA.
Our boat sits on a trailer, in our driveway, exposed to the weather, connected to shorepower 24/7. I keep (2) thermostatically control heaters running in the cabin/berth areas. I also shut off water to the swimstep shower and drain water.
So now to your question. Our VP D4-320 engine is NOT self-draining... bummer, VP should think like an owner! Rather than run pink antifreeze thru the heat-exchanger system, I'm choosing to utilize a bilge heater. I intend to locate it in the aft compartment behind motor. I will plug it into the AC GFCI power outlet in the Kisae inverter-charger. I also have a heater / dehumidifier I will locate somewhere in the engine compartment.
Hope this helps a bit... good luck!
Bob
Kimberly Dawn