Steve,
I'd be curious to see how cold it gets near the engine in a sailboat
sitting in Hood Canal in winter. I doubt the temperature of the salt water
gets below 40 F and if the boat is sitting in it, the boat should stay that
temp. Also seawater freezing temp is about 28.4 F .
I can't see a block freezing and breaking in those conditions,
Now if the boat is on the hard, different story.
Gordon

"Steve" wrote in message
...

"Roger Long" wrote in message
...
Can anyone out there give me some informed and real world (yeah, I know
this is a newsgroup but, hope springs eternal) insight as to how
vulnerable raw water cooled engines are to damage from freezing?


My Volvo is designed for sea water cooling and each cylinder jacket,
manifold and the OEM "water lift muffler" has a drain cock. Seems like a
lot
to remember each fall but these drain every drop of water from the block.
To
prevent these cast iron surfaces from rusting over the winter, I have
three-way sea cock that allows me to pump anti freeze into the system. I
don't actually do this, here in PacNW, since the temp never get that cold
in
my boat (heater) and I like to have the option to go out for you sail when
the winter weather is nice.

Check the location of your drain cocks on you Yanmar, see if they drain
all
the lowest points.

I happen to have a small Volvo MD7A here with a cracked exhaust manifold
because this model didn't have a drain cock and it must have frozen the
standing water. Such a drain cock would have saved this nice little
engine.

Now I'm rambling. Sorry.

Steve
s/v Good Intentions