Unwinterized yacht in arctic Texas-Questions for my Yankee Hatteras friends & experts

[52CMY]

My redundant contingency plans for a historic Texas winter storm fell through.
My prior visions of being onboard to test and opcheck genset, inspect lines and remove liquids less than 80 proof from the aft deck & dockboxes didn't happen. But I'm stranded 300 miles away.
So when the ice storm hit Houston, and the TX power grid failed at 2am two nights ago, despite the great efforts of my boat neighbors and marina management, I ended up with total AC power failure (shorepower out & GenSet failure to start), ER vents not sealed, and all the through hulls open. 15degF with up to 20-25knots frigid wind on the bow, dock and steps covered in ice. Internet obviously down so Blink webcams w/temp sensors unavailable.
The only saving grace was 50deg seawater temp of (brackish) Galveston Bay, and that the 4 x HVACs had been warming the interior till total AC power failure...but that didn't keep my mind racing the last two nights of unprecedented crazy low wind chills and temps regarding level of risk and potential outcomes.
My guess is that a 68K lb Hatteras with full water and fuel tanks in 50 deg water with the interior warmed to 60 degs would take many days of 0deg temps in calm winds before something broke. Obviously frigid winds blowing into the engine room is bad and would cut that time down, but by how much?.
Anyone have a rule of thumb or experience they can share? What freezes and fails first? What's the weakest link? Any surprises?

(note: power came back on at boat this am and apparently there was no damage)

[Freeebird]

Is this still "a friend's" boat we're talking about?

[SKYCHENEY]

Water is warm enough not to worry about thru hulls. The problem would be domestic water lines. The lines furthest away from the waterline would probably freeze first. If you have a fresh water washdown or an ice maker on the aft deck or something like that.

[52CMY]

Water is warm enough not to worry about thru hulls. The problem would be domestic water lines. The lines furthest away from the waterline would probably freeze first. If you have a fresh water washdown or an ice maker on the aft deck or something like that.

I got the neighbors to drain the Deck fresh water washdown lines but forgot about my transom hand shower (so it clearly perished in the hard freeze).

I agree that the thru hulls wont freeze but concerned that the exposed HVAC line fittings and pumps in the ER might freeze and pop, creating a flooding event when they thaw with the open thru hulls. I don't have good feel for how much ER ventilation occurs when there's 20-30knots of wind on the nose.
--my guess is that the 53deg (now 48deg) Galveston Bay SST trumps all during a 2 day deep freeze event and freeze damage is going to be limited to Aft deck (potable water lines & exploding soft drink/beer cans). I think I was lucky.

[Dan Mapes]

It takes a couple of days of a hard freeze before one has to worry IMHO. So if it warms up during the day you are probably good to go. If you were on the hard it would certainly be a different story.

[oscarvan]

There are (only) 7 through hulls on my 53 and it takes less than 2 minutes to close all of them, and really no time at all when I do them as I work my way through the boat for the "Leaving Ship" routine. Food for thought.

[SeaEric]

Water temp is everything IMHO. You're probably fine. "Wind chill" means nothing to inanimate objects.

[oscarvan]

"Wind chill" means nothing to inanimate objects.

Correct. But a stiff breeze coming into the cracks will reduce the time it holds its heat after the heaters die.

[Photolomy]

I find it hard to believe that anything "inside" a yacht like this floating in 50 deg water would freeze. Is that actually an issue?

[Captain Ralph]

I find it hard to believe that anything "inside" a yacht like this floating in 50 deg water would freeze. Is that actually an issue?

I remember one of my boats caught unprepared in a freeze (December 1989). Snow-mostly ice covered the engine deck hatch in inches.
The surrounding river water that the boat was above (boat in lift), did not freeze.

Found no issues days later when I was able to access the boat.

If your boat is in the water, IMO; you should have no issues.

December 1989, I 95 was closed in Jacksonville FL. All bridges and over passes closed because of ICE from way up north to Daytona. Only time in history the area shopping malls were closed in Jax, cheapest Christmas in my life...