Last week, with the weather forecast calling for much colder temps, I
did a quick, temporary winterization of my 4 cylinder Volvo by letting
the water pump suck in two gallons of RV antifreeze after the engine
had been brought up to operating temperature. To be sure the
antifreeze had made it through the system, I captured what was dripping
out of the outdrive bellows in an empty water bottle after I shut the
engine off. I decided I would keep this bottle of antifreeze near the
boat to see if it would ever freeze up. Since last week when I did
this we have had some unseasonably cold temps and signicant snowfall
here (South Lake Tahoe, CA); the high in past two days was 36F with a
low of 6F this morning. This morning I checked the bottle of
antifreeze and the contents was slushy. Now I am worried about
possible damage due to freezing. Should I be concerned or does it take
a longer, hard freeze than this to do damage?

By the way, I plan on taking my boat down to a warmer climate this
weekend for it's yearly winter storage.

Thanks,
Bob