BUKH DV10 zinc anode sheared.

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Nicholas123

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Is this a common problem?
I am left with about a inch & a quarter stuck in the hole & think it would be wise to leave it there for fear of bits breaking off & blocking the water jacket but would be interested to hear of other peoples experiences.
It would appear that the previous owner used a 1/2" one when the original was 12mm.
 
Most users seem to knock them in so a new one can be fitted. You might be successful with an Easi-out but you will probably push it inside trying. Trouble with leaving it in the hole is that little water can get to it so it won't be doing much.
 
I have never been able to understand quite what the tiny pencil anode is supposed to protect? ..... the entire massive cast-iron block? .... in which case it must certainly contradict the usual 'theory' that the anode needs to be able to 'see' the metal it is protecting? I do not accept the argument that 'it wears away, so must me doing some good' .... hardly surprising given the massive amount of steel surrounding it.
 
vyv_cox said:
Most users seem to knock them in so a new one can be fitted. You might be successful with an Easi-out but you will probably push it inside trying. Trouble with leaving it in the hole is that little water can get to it so it won't be doing much.
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It is about an inch & a half long & if you pushed it in (you might be able to do this as judging by the spare one I have inherited it only seems to wear at the tip) but if you did that you would loose contact with the retaining nut to which the thing is tethered & that would also sever electrical contact.......you would also only be able to inch it forward very slowly over a period as it wears down & I can see that taking possibly years to clear the whole inch & a half.(I'd be worried about bits dropping off & blocking the main artery/water way).
The one that is broken off in there looks to be to big which is why it jammed & sheared off & very little water looks like it got behind it anyway.
I have considered drilling & tapping a new thread & then extracting it using a washer across the entrance & an extra long screw to withdraw it but as the boat is in Belgium I don't want to take any unnecessary risks that may hold up my progress.Winter is coming on! Also as Vic mentions it is hard to see the thing did a very remarkable job in the first place.
I might tinker with it when I get back.Thanks for your advice.
 
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I always used to knock the remains through into the water jacket and fit a new anode.

What I now do is to reduce the diameter of the new anode by a couple of millimetres (I use a lathe but you could do it with a file).
 
parsifal said:
I always used to knock the remains through into the water jacket and fit a new anode.

What I now do is to reduce the diameter of the new anode by a couple of millimetres (I use a lathe but you could do it with a file).
Click to expand...

I reckon there must be 1 1/4" of very solid anode to be knocked through into how big a water way beyond it? Looks like a risky business to me.
 
Mine was extremely well held in place with corrosion, so I was able to drill it out with progressively larger drill sizes meaning it was effectively removed as shavings. I agree that having the whole thing loose in there may not be a good idea.
I've heard of older Bukhs and Volvos with sea-water cooling where the anodes eat away very quickly and thoroughly. I think this is when they're working correctly.
My theory was that when the engine is ashore or un-used for a long period, the white corrosion that grows around the anode due to being exposed to oxygen is non-conductive, so the anode is effectively insulated from the metal it around thus doesn't work as an anode any more. It's most important that the anode has a good electrical connection with the brass plug that it mounts on.
In fact this small anode does protect the mass of iron around it, if it's working correctly, it all depends on how quickly it's eating away. Think of the relatively few small anodes on the outside of the hull of a steel-hulled workboat, and the ratio in the engine is actually quite large.
These pencil anodes when fitted in the heat-exchangers of large Volvo-Penta marine diesels eat away very quickly so I'm fairly sure that when they get corroded stuck in place in small engines it means that they haven't been working properly. BUT it's just my theory and I may be wrong.
Hope this is in some way helpful anyway.
R
 
Having had the head off and cylinder liners out of my DV20 - there is plenty of room inside the water jacket for the old anode to drop to the bottom and quietly waste away if you just push it in. It would be good if you can extract the short length of stud that holds it to the brass screw-in cap, though. All the water in/outs are via the cylinder head so nothing to get blocked - unless you turn the engine upside-down!

Neil
 
I would knock it in without worry also.

Last year, I drained the engine water on a weekly basis, & rummaged around the inside of the drain hole with a paperclip. It was unbelievable the amount of used anode bits I managed to pick out over the season, 20-30 years worth i reckon (it would appear everything eventually makes its way to the bottom drain hole). I was able break up the bigger pieces with a small screwdriver.

You think the waterways are clear, until you drain again after a few hours running. Keep doing it, and you'll eventually get everything out.

(all this debris could have caused some localised heating, but I can't know that for sure - temp. guage was never out of the blue).
 
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neil_s said:
Having had the head off and cylinder liners out of my DV20 - there is plenty of room inside the water jacket for the old anode to drop to the bottom and quietly waste away if you just push it in. It would be good if you can extract the short length of stud that holds it to the brass screw-in cap, though. All the water in/outs are via the cylinder head so nothing to get blocked - unless you turn the engine upside-down!

Neil
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Agree absolutely for a dv20. There is a lot of space around the liners, the debris from the old one can happily sit at the bottom and although it will not do much good without positive contact it will slowly wear away. I am pretty certain the position of the dv10 equivlent is much the same so there is no water passage to block.
 
parsifal said:
If there was 1-1/4" of very solid anode left after one year's use it wouldn't be functioning as an anode, would it? :rolleyes:
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I don't know for sure that the one sheared off in the hole is 1 1/4" long but in a box of bits that came with the boat is one that would imply that is the case.The spare one in the box only has slight wearing away right at the tip so why the owner considered replacing it God only knows!
Like I said previously the one in the box measures 12mm while the one that has broken off in there is 1/2". That in itself is enough I should think to ensure that it broke off & I doubt it ever worked properly with a good flow of water round it if that is the way it is designed to work.Anybody know the correct diameter anode?

Thanks for all your advice,some good practical experience to go by.(I have been able to get the stainless steel screw out that came with the broken off lump & now feel that there is less pressure on me to come up with a radical solution).:)
 
joyfull said:
Where is the water drain plug for DV20. Is it worth draining?
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There isn’t one. If you are winterising just flush with fresh water, run the engine for a good 20mins with fresh water running into the strainer to warm it up and make sure the thermostat opens. Then run through a 50/50 mix of water and antifreeze. Stop before all the antifreeze has gone out. That’s it.
 
pvb said:
Vyv Cox seems to think there is, he mentions it in this article on fitting a calorifier to the engine - http://coxeng.co.uk/engine/calorifier-installation/
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I was going to say in the previous answer that there may be in a calorifier ‘add on’ but decided not to as the OP didn’t mention that. When I rebuilt my DV20 I don’t recall any water drain although it was 7 years ago!
 
The BUKH Parts Manual shows it in the starboard side of the engine block on the DV20.

On the DV10 it is on the port side, in a rather awkward place between the dipstick and the lift-pump.
 
The BUKH Parts Manual shows a drain cock instead of a brass plug and I have considered fitting one to make draining easier but I suppose a brass drain cock would be liable to seizing and would need rodding through.
 
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