That crust of ice is probably fresh water lying on top of the salt water.
Is there a creek or river entering the canal near your moorage? I've seen
that inside the marina at Pt Angeles.
Gordon
"Steve" wrote in message
...
I've seen a light crust of ice on the surface on a calm winter morning.
Even
though the sea water temp might get down into the high 30s or 40s, it is
the
outside air temp coming in through the ventilators that could freeze an
engine. My engine room is about 80% insulated, down to just above bilge
level, if outside air comes through the vents (always open), it could get
down to freezing.

Since I'm at the dock and paying a flat rate of $60 a month for electric.
I
keep a heater going along with a dehumidifier. I maintain a temp. of about
50-60 degrees in the cabin and engine room (door open). This is
recommended
to get the dehumidifier to work efficiently. I should mention, it get
about
two quarts of water a week even with the boat closed all week. I would
guess
about half comes from the air that I let in when I open the hatch and the
remainder through the cabin and engine room vents. I should mention that I
still have some main cabin hull left to insulate, however almost all of my
lockers are now insulated and lined.

Since I started using the humidifier, I haven't had any problem with mold
on
books, clothing or bedding.


--
My experience and opinion, FWIW
--
Steve
s/v Good Intentions


"Gordon" wrote in message
...
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