Until my recent migration sount, I lived it the Portland area since 1959 and owned a boat for the last 21 years I lived there. My winterization outine for the boat was:
1. Remove thermostat housing/thermostat and pour antifreeze into the motor until it starts to come out the jet.
2. Pour antifreeze into thermostat housing (and therefore into the exhaust logs) until is starts to come out the exhaust tips. If you have OT headers, pour slowly until you get anti-freeze out the weep holes would be my guess, my boat had logs.
3. Re-install the thermostat and thermostat housing.
4. Gas stabilizer for the fuel tanks and carb.
If the boat is stored in an attached garage, as mine was, this is the end of it.
If stored outside, under a tarp, you will need to protect the metal from moisture/corrosion and the interior from mold/mildew. Don't forget to prop the tarp up in the middle to help it from collecting puddles of rain water. Sweep the leaves off once in a while.
This is pretty much exactly the same way I have done it for the last twenty years. I have never freeze cracked a block yet. It doesn't have to be complicated. I use three gallons of antifreeze.