Winterising raw water cooled engines

[Scotty_Tradewind]

V

Not quite sure what you are trying to achieve here, Scotty. I would treat the coolant side first, change antifreeze, top it up, whatever, then do the seawater side. In most cases I see little benefit in putting antifreeze into the seawater side, I would prefer to drain it. If there is a significant ferrous content to the heat exchanger it might benefit from the corrosion inhibitor but in most modern engines there is nothing in there to corrode. IIRC you have a Bukh? In which case it could be useful but for my Yanmar there is only rubber, plastic and stainless steel in the seawater system, so no advantages.

A Bukh it is.

S

 

[ghostlymoron]

I asked this question a while ago and decided to just take the drain plug out over winter. No messing about with antifreeze.

 

[mihtjel]

A 'warm' engine will not have an open thermostat, it opens at around 60+ degrees.

Surely, a properly working thermostat opens slowly over a range of temperatures, 40-60C or similar, and is fully open at 60C - but also partly open way before that. That's at least the way I've been taught they work?

So while you might not get full flow through your engine, and should probably recirculate your antifreeze a few times, some of it will still pass through the engine.

Method I used most recently: Run the engine on fresh water for a while (rather a long while, as it turned out) to warm up, then run about 6-10 litres of antifreeze mix through it, and let it sit in the hose going to the pump. Same method has been used on several engines in the same yard, for several years - and we do have cold winters in Denmark, and have not had major epidemics of engines suffering freeze damage.

 

[vyv_cox]

Surely, a properly working thermostat opens slowly over a range of temperatures, 40-60C or similar, and is fully open at 60C - but also partly open way before that. That's at least the way I've been taught they work?

I confess I have not tested one from a raw water cooled engine but ones from cars do not behave as you describe. Opening occurs only a few degrees from the marked temperature, sometimes opening with a distinct 'pop'.

 

[mihtjel]

I confess I have not tested one from a raw water cooled engine but ones from cars do not behave as you describe. Opening occurs only a few degrees from the marked temperature, sometimes opening with a distinct 'pop'.

Hmm. Might be different for marine engines. Yanmar 1/2/3GM10/... thermostats are specified as follows:

Raw water opening temperature 42C +/- 2C, full open temperature 52C +/- 2C
Fresh water opening temperature 71C +/- 1.5C, full open temperature 85C (but also specified to open fully from 71C across 10C variation)

Pages 7-12 and 8-14 in the service manual for 1/2/3GM10/20/30 (and 3HM35)

 

[vyv_cox]

Hmm. Might be different for marine engines. Yanmar 1/2/3GM10/... thermostats are specified as follows:

Raw water opening temperature 42C +/- 2C, full open temperature 52C +/- 2C
Fresh water opening temperature 71C +/- 1.5C, full open temperature 85C (but also specified to open fully from 71C across 10C variation)

Pages 7-12 and 8-14 in the service manual for 1/2/3GM10/20/30 (and 3HM35)

My workshop manual for the same engines says the thermostat should commence to open at the temperature marked upon it. It should then be fully open 14 degrees C above that. It gives the procedure for testing, which is the one I have used for 50 years or more.

 

[VicS]

My workshop manual for the same engines says the thermostat should commence to open at the temperature marked upon it. It should then be fully open 14 degrees C above that. It gives the procedure for testing, which is the one I have used for 50 years or more.

Absolutely. AFAIK thermostats are always marked with the temperature at which they just begin to open. They may also be marked with the temperature at which they are fully open.

Heating too rapidly when testing can give a falsely high value. It can also be difficult to see the point at which they just begin to open.

 

[eddystone]

Well, that's the bypass corrosion and freeze protected then!

Yes that's what i thought later - at least the water round the engine is salt or brackish - I'll see if i can find an old blanket to put over the engine - just hope nothing has happened in the last month. I was just wondering - if the engine did freeze, would it automatically crack the block writing off the engine, or is there a plug somewhere which would be forced out?Would have thought the head gasket be the first thing to go?

If engineer has replaced water pump might have another go at winterising by taking out the t/stat. Alternatively, if the water pump isn't on the engine i.e. can't run it, if i took t/stat out and poured some anti-freeze through its seating would that permeate into block?