Winterizing a Yanmar 2QM20 - SailNet Community
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post #1 of 4 Old 10-10-2013 Thread Starter
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Winterizing a Yanmar 2QM20

It is that time of year. This is what I did today:

  • I am not a diesel mechanic
  • There are probably better ways to do this
  • This is what I did and it has worked for the last five winters
  • I live in Canada

The boat is on the hard. First I removed the thermostat

It takes a 10 mm socket to take out the two studs. Gently life the thermostat housing away to expose the thermostat.

This is where it was.

I lifted it out, cleaned it a bit and placed it on a clean cloth. I then replaced the thermostat housing with no thermostat inside it. I wanted to make sure the antifreeze went through the block, not bypass it.

In order to make the water go through the block, I pinch off the water line that "bypasses" the block.

I use a soft cloth wrapped around the water hose and then gently use a pair of vice grips. I normally use a much smaller pair, but they were at home.

Now I take the hose off of the "out side" of my water strainer. This hose leads directly to the engine water pump.

I have a big bucket into which I have installed a "thru hull" fitting. A piece of the right sized hose is permanently attached. I use a small barbed connector piece to connect the bucket hose to the water pump hose.

I get a water hose connected to the regular city water in the yard running outside over the cockpit. Once all is ready (pink antifreeze jugs handy and open, water running in the hose, key in the ignition) I fill the bucket about two inches above the thru hull and aim the hose back over the side.

I start the engine, look over the back to make sure water is getting thru. (It is a bit easier with two people but Linda was busy today). With water coming out the back I get down where the bucket is and as soon as the water is almost reaching the thru hull, I tilt the bucket, getting rid of more water and then pour in about two gallons of pink antifreeze. I make sure there is lots of pink stuff, go into the cockpit and check the water coming out. When I see it is really pink, I stop the engine.

Whatever pink stuff is left gets poured into all the sinks so I know there is antifreeze in the sink drain lines and not plain (freezable) water.

I hang a little sign by the battery switch that says "Thermostat out". (I have a good memory but it is short.)

In the spring I replace the thermostat after cleaning it and installing a new gasket under the housing.

If this is of help - super.

Just 252 days until launch.

Rik, Linda and Captain Hook
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post #2 of 4 Old 11-12-2013
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Re: Winterizing a Yanmar 2QM20

I've not taken out my thermostat. that seems a very good idea, I may just be pumping pink stuff around the engine rather than through it.

Bashing about on Lake Ontario and Beyond
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post #3 of 4 Old 11-13-2013
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Re: Winterizing a Yanmar 2QM20

nice write up.

Here's what I do with my 2QM20:
- drain the block at the two petcocks ... one near the oil dipstick, the other near the alternator.
- remove the impeller housing, and drain there as well
- drain the sea water strainer

but after reading this I wonder if I should do it your way instead ...

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post #4 of 4 Old 11-24-2013
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Re: Winterizing a Yanmar 2QM20

I have a 2gm20f and having trouble getting more then 1 gallon of AF through. When it starts, it starts to kick it out when the stainer output line is in a bucket! I decompressed the engine just to get the 1 gallon in, but now not taking any more. Is it the thermostat keeping it from circulating more? I got AF coming out of the drain by the dipstick so does that mean it at least got to the mixing elbow? Or could some lines already be frozen, there were one or two freezes but then melting temps here on the Hudson. I need to boost the battery to try to start it again, hopefully want to still get more in by holding the strainer line up and funneling it in, and have it come out the beck.
Any advice appreciated.
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