There are a few opinions about this subject.
Here in the north, most boaters, typically fishermen, tends to keep the rig down in the water(or sometimes, actually in thin ice also). The point is that the seawater transfer heat much better than air, so when the rig is in the water it will not freeze. Anyway as the rig is straight down, there will not be much water catched/Trapped in the area above waterline.
Off course there is a limit to everything.
When on trailer, i would definitely tilt the engine up and down a few times, there will be water left in the rig if only trimmed up for ones.
Antifreeze will certainly do no harm, even though i only used it on inboard engines. Hate to admit but the season is very soon over