Another question that comes to mind if the boat is on the hard when you do the winterization:
On the raw water cooled engines, wouldn't the engine need to be run long enough for it to warm up and for the thermostat to open? If the engine is cold when you run the anti-freeze through the system, won't the antifreeze largely bypass the engine block because of the closed thermostat?
I suppose you could bypass the thermostat by temporarily removing it.
In a system equipped with a heat exchanger, you only have to worry about filling the intake lines, exchanger, and exhaust with anti-freeze, since the engine block already contains it.