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cold night. should i be worried


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Local mechanic buddy of mine says this to me every year when I start to freak out in the fall.   You need a night well below freezing with it not getting above freezing the next day and then back down the following night.   You said it's in the water.  That should help you out.   It should only be below freezing for a couple hours.  You need several hours below freezing to crack. 

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What causes the damage is the expansion of the volume of water.  Frozen water at 32 degree has about the same volume as liquid water at 33, so just because it's frozen doesn't mean it will cause any trouble.  The volume at 29 isn't that much different.  It's not until you get down to maybe 25 degrees does the volume increase enough to do damage.

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Do you have easy access to the boat? If so I would take the 15 minutes to drain the block and or heater. Especially if you have a heater.

As said above I have heard that it takes a solid 8 hours of the actual block being below freezing for the water in it to freeze. But I never want to personally prove that statement, so I always just drain everything to be safe. Plus it gives me an excuse to go work on the boat ;)

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Get up every 2 hours, swim out to the boat and start it up for about 15 minutes to keep it warm.  Then go back to bed.  Like having a newborn.

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1 hour ago, MadMan said:

What causes the damage is the expansion of the volume of water.  Frozen water at 32 degree has about the same volume as liquid water at 33, so just because it's frozen doesn't mean it will cause any trouble.  The volume at 29 isn't that much different.  It's not until you get down to maybe 25 degrees does the volume increase enough to do damage.

Practically speaking, water does not change volume due to temperature until it freezes, then it expands about 9% as it freezes.  So water at 32 degrees is the same volume as water at 70 degrees but ice at 32 degrees has 9% greater volume.  If your block is below 32 for several hours it will freeze and crack something.  There is no slush phase.  All that being said, it takes quite a while for your block to catch up to the ambient temperature and I would not worry about a 29 degree night as long as the days before and after are in the high 30s or above.  If the boat is in the water then no problems at all.  The water will keep it warm.  We've left I/O's in the lake (drive unit in water) with temps in the low 20s with no issues.   If your boat is on a lift then do something like put a bilge heater in if the temps will drop to mid 20s or below or if there will be sustained temps below freezing (as your mechanic said).  Now if you have a heater or shower it has less thermal mass and is more susceptible to freezing.  Search from the home screen for several threads on this.

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sidekicknicholas

You should be just fine.

 

Easy things to do to help keep the block warmer :

* Drop the boat into the water, its a huge heat sync and if you're in it, you'll stay warmer

* Throw a heated blanket over the block

* Run a shop light on a timer, a light in the engine bay will heat the area up very quickly.

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11 minutes ago, sidekicknicholas said:

You should be just fine.

 

Easy things to do to help keep the block warmer :

* Drop the boat into the water, its a huge heat sync and if you're in it, you'll stay warmer

* Throw a heated blanket over the block

* Run a shop light on a timer, a light in the engine bay will heat the area up very quickly.

Might as well have taken the time to just drain the engine and heater after doing all of that...

I understand that he is probably fine and there is some things they can do to prevent it. But why risk it when it takes 15 minutes to drain everything and then know you are ok?

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2 hours ago, sidekicknicholas said:

You should be just fine.

 

Easy things to do to help keep the block warmer :

* Drop the boat into the water, its a huge heat sync and if you're in it, you'll stay warmer

* Throw a heated blanket over the block

* Run a shop light on a timer, a light in the engine bay will heat the area up very quickly.

Also known as a fire hazard.

Get the right tool for the job. It's called a bilge heater. Protect your investment.

With temps that high, you don't really need to worry about the engine block itself. But the peripherals are not nearly as sturdy, ie; your heater core, shower valve, water pump, etc.

Edited by Bill_AirJunky
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2 hours ago, minnmarker said:

Practically speaking, water does not change volume due to temperature until it freezes, then it expands about 9% as it freezes.  So water at 32 degrees is the same volume as water at 70 degrees but ice at 32 degrees has 9% greater volume.  If your block is below 32 for several hours it will freeze and crack something.  There is no slush phase.  All that being said, it takes quite a while for your block to catch up to the ambient temperature and I would not worry about a 29 degree night as long as the days before and after are in the high 30s or above.  If the boat is in the water then no problems at all.  The water will keep it warm.  We've left I/O's in the lake (drive unit in water) with temps in the low 20s with no issues.   If your boat is on a lift then do something like put a bilge heater in if the temps will drop to mid 20s or below or if there will be sustained temps below freezing (as your mechanic said).  Now if you have a heater or shower it has less thermal mass and is more susceptible to freezing.  Search from the home screen for several threads on this.

Water does not expand 9% at 32 degrees (0 degrees C). This graph explains it (density is the inverse of volume).  Also 29F = -1.6C.

 

maximum_density.gif

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16 minutes ago, MadMan said:

Water does not expand 9% at 32 degrees (0 degrees C). This graph explains it (density is the inverse of volume).  Also 29F = -1.6C.

 

maximum_density.gif

When water freezes (crystalizes) it's density goes down about 9% and volume correspondingly goes up 9%.  In the liquid phase (> 0C) water is quite stable in volume at different temperatures (within normal environmental range) - varying no ore than 1% from 32 degrees to 100 degree F.  That would be from zero to about 40 on your graph.  Not sure where the data for everything left of zero C on your graph came from?  When water gets to zero C it continues to loose heat but stays at 0 until it looses sufficient heat (exothermic process) until it changes into the solid phase, during which it expands about 9%. It is more of a step on a graph, not a curve, and it all happens at zero.  Just physics.  See references.

http://water.usgs.gov/edu/density.html

http://chemistry.elmhurst.edu/vchembook/122Adensityice.html

Or just plug temperatures into this calculator and then click on water and then ice:

http://www.had2know.com/academics/water-ice-density-temperature-calculator.html

Point is that if you let your water filled block get to 31F (which may take some time), it will crack.

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