With boat in water how cold before need antifreez?

R

RM

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468
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Boat is still in water on Chesapeake and plan on leaving there for a couple more weeks. Water temps last weekend were still in the low 50s/upper 40s but we are having a cold stetch here with air temp for days in the 40s and nights in the upper 20s/low30s.

How cold does it need to get before I need to add antifreeze to freshwater lines and engines? I am thinking the heat radiating up should be plenty to keep the freshwater lines thawed and the motors are FWC so should be OK too as inboard.

Notcied the garden hose was frozen this morning so got me thinking. Thoughts?
 
Is it an enclosed boat? If it is, you should be good for at least 3-4 weeks, maybe longer.
I'm on the lower Potomac and have gone as late as Dec. 23 to winterize.
 
Just cold enough for water to freeze. I certainly wouldn't chance it in my boat.
 
Just went to my boat tonight. Water temmp was 43 degrees. Bilge was 40+, ambient was 33. I have most done but still have to do my genny, heads and a/c's. not too worried but will finish this w/e. I'm on the upper chessy.
Chris
 
I am on the lower Appomattox. I did not winterize last winter and will not this year. I do have a couple of golden rods in the bilge to quell condensation. I have the luxury of having Horizons. When we had a couple of cold snaps I merely drained the raw water side by pumping air into it. However, beyond that, I do not worry if the daytime temps are over 35*F. The green house effect coupled with the golden rods and protected waters keeps the bilge well over 32*F. I stress the gennie once per week as well as bringing the engine up to temp as well. If we are expecting a one night cold snap, I do the same on the way home from work.
 
As long as the nights are in the upper 20's or higher and the day time temps in the 40's, I don't think anything will freeze up. The two most common variables are the temperature the water is exposed to and how long these temperatures are present. The lower the temperature of the air the quicker the freezing. The longer the water is exposed to freezing temperatures the more likely it will freeze. It takes 3-4 hours for me to make ice cubes in a 10* freezer with cold tap water. If the freezer were at 28* I don't know how long it would take but it would be at least 2x to 4x longer. It takes a lot of energy to convert water from a liquid to a solid. Once the water hits the temperature of changing phases it takes a while for this to happen. If the engines are raw water cooled with salt water, that water will freeze at a lower temperature, perhaps 30* instead of 32*. Just a note here. We talk about the freezing point being 32* but this is also the melting point as as well.
The biggest risk you are taking is hoping for continued mild temperatures. A day or two of mid thirty degrees and low in the teens could be expensive.
 
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