Dealing with a rusty raw water cooled engine

[seaangler23]

There was no lime scale it was rust build up, I need to adapt some anodes to fit it next

 

[johnalison]

It used to be part of my winter lay-up in the last seawater-cooled engine I had to run the engine through with inhibiting oil, using antifreeze with it for the last flush. It was supposed to coat the passages, for the winter anyway.

 

[NormanS]

That is certainly not a pretty sight

Hydrochloric acid may well clean it up but Id be afraid of overdoing it and ending up with a load of leaks

BTW not all brick cleaners are hydrochloric acid based. you will have to consult the labelling or the safety documentation to be sure.

I think if the engine was originally fitted with anodes I would move making some new ones up the list of priorities. Remember though any old zinc will not do. Get some bar of the correct specification or you will be wasting your time and effort.

Information please, VicS. I had just assumed that zinc anodes were made from zinc. What's the correct specification? I ask because I make my own prop anodes.

 

[vyv_cox]

Information please, VicS. I had just assumed that zinc anodes were made from zinc. What's the correct specification? I ask because I make my own prop anodes.

The information is contained in this link http://www.boatzincs.com/use_milspec_a18001k.html which although commercial includes the standard it relates to. Very small amounts of iron in the zinc will almost totally prevent it from working, definitely a problem for DIY recovery of old anodes.

 

[NormanS]

Thanks for that. I see that your link talks about the danger of a layer of white encrustation on the anode, preventing it from doing its job. Strangely, my (bought) pear shaped anode seems to get this worse than my (home-made) Autoprop anode. Maybe I'm doing something right or maybe it's something to do with the more stationary life style of the pear anode. Interesting though.

 

[vyv_cox]

Thanks for that. I see that your link talks about the danger of a layer of white encrustation on the anode, preventing it from doing its job. Strangely, my (bought) pear shaped anode seems to get this worse than my (home-made) Autoprop anode. Maybe I'm doing something right or maybe it's something to do with the more stationary life style of the pear anode. Interesting though.

I have always thought that the white layer (zinc hydroxide?) on anodes, and chain, is more to do with the water quality than anything else. When we kept the boat in fresh water the hydroxide accumulation on anodes was quite considerable, whereas in only seawater it is not too bad. Chain definitely accumulates less if it is kept as dry as possible on a pallet or hanging off the cradle than in the anchor locker all winter. This pic illustrates it well. It shows the galvanised cradle under my boat, with the position of a rope that was tied on it all winter clearly marked in white. Presumably the rope was wet far more often than the rest of it, plus access of air to it was more limited.