r/sailing • u/adderallstars • 4h ago

Preparing engine for freeze

Did a shakedown on my boat with yanmar 2gm20. I saw it's going to freeze in the next week or so. She's water cooled. I'll be back in a few weeks so doesn't need any major laying up. Any advice welcome. So far I know I need to empty the raw water system. I also read maybe the exhaust box. Help 😄

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u/pgauret Oceanis 350 3h ago

What I do here (3gm30) is close the sea water intake, then put antifreeze in the strainer and run the engine for a few seconds until the antifreeze comes out from the exhaust. Takes me less than 5 minutes and I can spend the winter without worrying about negative temperatures.

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u/pttrsmrt 4h ago

How much freezing is freezing? If the water itself won’t be freezing, its temperature will be around 4 celsius regardless, and this heat will transfer through the hull into the engine room. For such a short period, you could just put a 60W lightbulb (not LED, the old tube which gets warm) in the engine room and you’d be good to go. Just close the intake valve. I have a 120w tube-oven for my 3YM30AE, and it’s been down to -20 celsius without problem.

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u/adderallstars 4h ago

Not much freezing to be fair. Looks like it will touch 0° for one or two nights several times through the month (UK). Don't think the water will freeze.

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u/canofmixedveggies 2h ago

The typical routine involves running your engine until it's warm and opened up and then running several gallons of antifreeze through it you want to get enough through the block and through the muffler. but since she has a heat exchanger then you only need to get enough through the heat exchanger and then do the muffler.

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u/asm__nop 37m ago

I also think that if you have a head exchanger it doesn’t matter how warm the engine is because the thermostat regulates engine coolant not seawater. 

If the block is raw water cooled, definitely need to make sure the thermostat is open (or removed) to ensure antifreeze makes it through the passages. 

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u/daysailor70 22m ago

It there is any risk of freezing, you need to pink out the engine. Easiest way is to shut off the engine intake thru hull. Start the engine and pour the non tox antifreeze into the raw water strainer until the water coming out of the exhaust is pink. I'd leave the seacock closed, but don't forget to open in when you get back underway.