Winterising raw water circuit

[eddystone]

I'm new to indirect cooled engines. Previously I just used to close the raw water inlet, open the top of the strainer start the the engine and pour in antifreeze mixture long enough to circulate around the engine, provided the thermostat was open. Now I'm wondering, as the fresh water bit is protected by anti-freeze, what do do about the rest; I would think the heat exchanger is most at risk.
Up until now I haven't bothered as; a) the night time air temperature down on the Tamar has barely gone below zero; b) its brackish water; c) there's lots of tidal movement; d) the temperature inside the engine box is a couple of degrees higher than outside. However, even in the balmy south west, freezing conditions are possible as was the case last February.

 

[Balticfly]

Do something similar. Put the inlet hose into fresh water and run through the engine (from a bucket or two) then run an antifreeze/coolant mix till you see it coming out pink or whatever. Then close your hoses. Better to have coolant sitting in the engine over winter than salt or brackish water.

 

[Rafiki]

Dont forget the calorifier if you have one. That will have fersh water in it and should be drained down to prevent freezing and splitting.

 

[ctva]

I'm new to indirect cooled engines. Previously I just used to close the raw water inlet, open the top of the strainer start the the engine and pour in antifreeze mixture long enough to circulate around the engine, provided the thermostat was open. Now I'm wondering, as the fresh water bit is protected by anti-freeze, what do do about the rest; I would think the heat exchanger is most at risk.
Up until now I haven't bothered as; a) the night time air temperature down on the Tamar has barely gone below zero; b) its brackish water; c) there's lots of tidal movement; d) the temperature inside the engine box is a couple of degrees higher than outside. However, even in the balmy south west, freezing conditions are possible as was the case last February.

The process is no different with either direct or indirect raw water cooling. Just make sure the engine is up to temp to allow the coolant to circulate in all parts of the engine.

 

[prv]

Just make sure the engine is up to temp to allow the coolant to circulate in all parts of the engine.

That part’s not necessary - the thermostat is in the fresh side, which is already filled throughout with coolant mix having an antifreeze function. He just needs to get his temporary antifreeze into all of the raw-water side, which isn’t very long (typically just pump, heat exchanger, exhaust elbow) and doesn’t open or close with temperature.

Pete

 

[Dull Spark]

If you drain the heat exchanger and remove the raw water impeller, then the only seawater left in the system is the stuff in the box downstream of the engine exhaust. That should have room for expansion in a freeze, so is there a need for an antifreeze flush?

 

[RichardS]

If you drain the heat exchanger and remove the raw water impeller, then the only seawater left in the system is the stuff in the box downstream of the engine exhaust. That should have room for expansion in a freeze, so is there a need for an antifreeze flush?

It's a very good point which we have discussed on several precious occasions. However, it seems to be one of those issues which polarises into two different viewpoints which sometimes coalesce over the anti-corrosive benefits of an antifreeze flush.

Richard

 

[peteK]

Never bothered.

 

[ctva]

That part’s not necessary - the thermostat is in the fresh side, which is already filled throughout with coolant mix having an antifreeze function. He just needs to get his temporary antifreeze into all of the raw-water side, which isn’t very long (typically just pump, heat exchanger, exhaust elbow) and doesn’t open or close with temperature.

Pete

Cheers, every day a school day.

 

[Pavalijo]

I shut the seawater intake, removed the lid on the raw water strainer - first mate turned engine on, I poured antifreeze into the strainer and first mate shouted when the antifreeze appeared and turned off the engine. I then opened the intake seacock to drop out any seawater before the strainer.

And yes - drain down the calorifier as well as you can - I then put rags and old towels around the connections and relief valve to insulate them in case any water remained there. I also removed the water pump and took that home with me.

That was before we hit the Spanish Rias - the yard assures me that the temperature will not drop below 5c in Ria Arousa. Haven't seen it get near that yet!

 

[BabaYaga]

If you drain the heat exchanger ?

Fully draining this is sometimes difficult. Anti freeze=peace of mind.

 

[jwilson]

Also remove any shower spray fitting on a transom shower - first thing to freeze and crack. If really expecting prolonged cold drain down fresh water, run pumps till empty and leave taps open. I don't usually go that far, prefer to leave a small oil-filled electric heater onboard on a thermostat.