Engine Anodes and Fresh Water

[alan_d]

Following on from the discussions about winterising directly-cooled engines, how is my engine anode likely to respond to being surrounded by fresh water and antifreeze?

I know that a period of time in fresh water stops zinc hull and shaft anodes from working, but what about the pencil anode in my Bukh DV20? Provided I use enough antifreeze I should not have to worry about corrosion over the winter, but what about next season? Should I change the anode in the springtime even though there is plenty of metal left, or would scraping/sanding it do? Or am I worrying about nothing?

 

[Twister_Ken]

I suspect you are worrying about nothing.

Whenever I've changed my Bukh anode it has been dry. Neither does water pour out of the block when it is removed. Placed at the top of the engine I don't think it is permanently underwater, just when the engine is running and water is flowing around it.

 

[alan_d]

I suspect you are worrying about nothing.

Thanks TK, that's the sort of answer I like.

I was expecting something more along the lines of:

• It is vital that you replace the anode every three months regardless.
• I've replaced my anodes with ones turned out of iroko and they're fine.
• What are you doing with a directly-cooled engine anyway, dont you know that it will rot away internally while you watch?
• Don't use antifreeze, you will poison the Earth.

 

[Twister_Ken]

Of course, I didn't mention the presence of eels living in the engine block, because I didn't want to worry you.

 

[wotayottie]

Simply take the anode out and leave it out if you arent running the engine.

Our boat lives in fresh water so I can vouch for the fact that zinc anodes do become ineffective with a hard white crust if you leave them in fresh. So we use aluminium anodes.

 

[samwise]

Thanks TK, that's the sort of answer I like.

I was expecting something more along the lines of:

• It is vital that you replace the anode every three months regardless.
• I've replaced my anodes with ones turned out of iroko and they're fine.
• What are you doing with a directly-cooled engine anyway, dont you know that it will rot away internally while you watch?
• Don't use antifreeze, you will poison the Earth.

Never use Iroko anodes in a cast iron block. Mahogany is the only answer!

 

[alan_d]

Simply take the anode out and leave it out if you arent running the engine.

Yes, that makes sense. It is unlikely to do any good over the winter because if I've put enough antifreeze in it will not be necessary, if I haven't put enough antifreeze in it will become passivated and do nothing, and anyway it will probably be high and dry as Twister_Ken suggests.

 

[alan_d]

Whenever I've changed my Bukh anode it has been dry. Neither does water pour out of the block when it is removed. Placed at the top of the engine I don't think it is permanently underwater, just when the engine is running and water is flowing around it.

Update
I have just run antifreeze through the raw-water system. I then removed the impeller, after which I took the anode out, and as I did so about half a pint of antifreeze solution ran out. In my engine, at least, it does seems as though the anode would normally remain immersed.

 

[Bronze Age Man]

Any of you have a good picture of the anode nut location, not sure about mine. The manual picture is useless & one pic on line too vauge.