Descaling Bukh 20 with Rydlyme

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davidmh

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I want to descale the engine over the winter and plane to do by circulating the mixture through the block with a small pump in a bucket, returned the mixture to the bucket. I have read that this can be done. I know I need to remove the anode from the block before I start. I will also need to remove the thermostat. On the Bukh the thermostat is mounted on a housing on top of the block and seals with a rubber O ring fitted around the thermostat.
1. If I take the O ring off the thermostat and then fit just the seal into the housing will it seal . Have any of the Bukh owners done this, maybe you have done if you have had a thermostat fail shut and have needed to run the engine.
2. I need a small pump for the Rydlyme, I will have mains power, I feel a low volume pump would be adequate as it simply needs to keep the mixture circulating. Any suggestions on a pump, Lidl, Aldi. Machine mart?
3. Would it be any benefit to use warm/hot water.
4. How long would you run the pump for?
Look forward to the forum comments
David MH
 
I have done it on a Bukh DV20. I used a small, cheap, 12v submersible water pump from the chandlers- like a tube shaped thing. I just fitted some simple hosepipe to it which conveniently fitted the tube coming off the T on the front of the engine. The diluted ridlyme was in the bucket and circulated merrily for half and hour or so (I can’t swear to how long, this was in 2018) until it stopped fizzing.
FCB72F3C-3F8C-45EF-8F15-2BEE50F26661.jpeg
 
You are correct that you only need low volume pump ... and the pump that Charlie Boy used is ideal ....

But you say its raw water cooled - re-routing water - How will you cool the exhaust if water usually exits that way ?
 
Charlie Boy said:
Having dismantled this engine a few years ago I can tell you that the build up of crap inside is quite spectacular. Mine is raw water, the heat exchanger version may be better of course.
Click to expand...
That's interesting because when I changed the liner of my 1982-installed raw-water cooled BUKH DV10 (which I have owned since 1997) a few years ago there was no scaling; just some light surface rust. Also the engine does not overheat.

One thing I did find inside was a little collection of the remains of zinc anodes, which had obviously failed to come out with the brass anode-holder and been punched through!
 
One aspect of Raw Water cooled engines .........

Various engine manuals such as Perkins advise against running raw engine cooling at same temperature as indirect. The reason being that the raw water can deposit salts in the channels which indirect will not do - particularly that you usually have Glycol / Additive in indirect as well.
I actually took the Thermostat out of my Perkins when I had it fitted so raw water cools her more than indirect (which she was originally). The Heat exchanger collapsed inside - so removed it.
Such as Perkins advise to control engine temp by use of the seawater intake valve for raw systems ... me ? I have it full open and I know I will have no salt deposits !!
Each winter I close valve - open top - remove gauze filter and when engine running ... pour 10ltrs of Antifreeze in the top of the seavalve body ... pipe on exhaust to large bin to collect it after passing through ...
 
PS, with hindsight and looking at the set up I have there, I’d have clamped the textile covered pipe that leads from the T to the front of the thermostat thereby forcing the Ridlyme through the block rather than taking the easy route straight to the ‘stat.
 
Charlie Boy said:
I have done it on a Bukh DV20. I used a small, cheap, 12v submersible water pump from the chandlers- like a tube shaped thing. I just fitted some simple hosepipe to it which conveniently fitted the tube coming off the T on the front of the engine. The diluted ridlyme was in the bucket and circulated merrily for half and hour or so (I can’t swear to how long, this was in 2018) until it stopped fizzing.
View attachment 137064
Click to expand...
remove the thermostsat and block the bypass hose then its all going through the block.
 
Refueler said:
One aspect of Raw Water cooled engines .........

Various engine manuals such as Perkins advise against running raw engine cooling at same temperature as indirect. The reason being that the raw water can deposit salts in the channels which indirect will not do - particularly that you usually have Glycol / Additive in indirect as well.
I actually took the Thermostat out of my Perkins when I had it fitted so raw water cools her more than indirect (which she was originally). The Heat exchanger collapsed inside - so removed it.
Such as Perkins advise to control engine temp by use of the seawater intake valve for raw systems ... me ? I have it full open and I know I will have no salt deposits !!
Each winter I close valve - open top - remove gauze filter and when engine running ... pour 10ltrs of Antifreeze in the top of the seavalve body ... pipe on exhaust to large bin to collect it after passing through ...
Click to expand...
Removing the thermostat may have the opposite effect than was intended. On the Bukh and other engines the thermostat has a dual function, opening the flow into the engine and closing off the bypass. Removing the thermostat allows all water to bypass the engine, which will overheat.
 
vyv_cox said:
Removing the thermostat may have the opposite effect than was intended. On the Bukh and other engines the thermostat has a dual function, opening the flow into the engine and closing off the bypass. Removing the thermostat allows all water to bypass the engine, which will overheat.
Click to expand...
when i bought my cobra 850 someone had removed the thermostat and this caused the engine to overheat . Being a total novice to boats it took a lot of google and research to realise how important a thermostat is in a bukh. Im not sure if it would run ok without the thermostat if the bypass pipe was pinched so i bought a new one. Now it runs fine and never overheats.
 
Thanks for all your replies. Charlie Boy's photo is what i had in mind. Charlie Boy is the pump you show one normally sold for boat freshwater systems? I will not have the engine running when I do the descaling. I will just leave it circulating with the Rydlyme in it and then flush out with fresh water. The reason I want to remove the thermostat and pinch the bypass tube is so that all the rydlyme circulates throughout the block. With a cold engine the Buhk thermostat is closed and all the water goes through the bypass to the exhaust, as the temperature rises the thermostat opens and and allows cold water into the block and at the same time restricts the flow of the bypass water. The question is how do I seal the thermostat housing top cover without the thermostat? I thought I could use the thermostat O ring to seal it. Anyone done this.
David MH
 
Refueler said:
But you say its raw water cooled - re-routing water - How will you cool the exhaust if water usually exits that way ?
Click to expand...

The engine is not run during the flushing.

Refueler said:
One aspect of Raw Water cooled engines .........

Various engine manuals such as Perkins advise against running raw engine cooling at same temperature as indirect. The reason being that the raw water can deposit salts in the channels which indirect will not do
Click to expand...

The issue is that if you run a raw water engine at 'ideal' temperature for the engine efficiency the salts will be deposited very rapidly from seawater. Hence raw water (direct) cooled engines are run cooler than freshwater (indirect) cooled ones, at a slight cost in e.g. fuel consumption. (Bukh manual advises indirect cooling if you do more than 500 hours per annum.)

Bukh has two different thermostats for direct or indirect cooled engines, which open at different temperatures. ( I imagine other engine suppliers do likewise.) It is important to have the correct one for the type of cooling you have. The direct cooled DV10 & 20 engines should be run at 50-75 degrees C (DV10/20 Owners Manual), while the indirect are run at IIRC 70-95 degrees C. (DV36 Owners Manual specifies 50-70 for direct cooling, 70-90 for indirect.)

Even a direct cooled engine run at the correct temperature will, especially one run in seawater, gradually build up salts deposits and collect sand and shell etc. fragments. Eventually this will cause the engine to run at excessive temperatures (above that specified), which will in turn accelerate scaling, even if all other elements of the cooling system are good, . That is what the acid flushing is intended to correct.
 
On removing my stat ( dv 24 ) , to check if it was correct I found it embossed with the number 60. Mine is also raw water cooled I assume this 60 indicates the correct stat , however it only starts to open at 70 degrees ( pan of boiling water check ) . May be the stat is out of calibration, as my dual display ( raw and fresh water ) temp gauge still hangs in the red zone too long . So looks like an acid flush for me also .
 
wingcommander said:
On removing my stat ( dv 24 ) , to check if it was correct I found it embossed with the number 60. Mine is also raw water cooled I assume this 60 indicates the correct stat , however it only starts to open at 70 degrees ( pan of boiling water check ) . May be the stat is out of calibration, as my dual display ( raw and fresh water ) temp gauge still hangs in the red zone too long . So looks like an acid flush for me also .
Click to expand...

The thermostat should just start to open at 60°C. If it starts to open at 70°C it's time to replace.
 
davidmh said:
I want to descale the engine over the winter and plane to do by circulating the mixture through the block with a small pump in a bucket, returned the mixture to the bucket. I have read that this can be done. I know I need to remove the anode from the block before I start. I will also need to remove the thermostat. On the Bukh the thermostat is mounted on a housing on top of the block and seals with a rubber O ring fitted around the thermostat.
1. If I take the O ring off the thermostat and then fit just the seal into the housing will it seal . Have any of the Bukh owners done this, maybe you have done if you have had a thermostat fail shut and have needed to run the engine.
2. I need a small pump for the Rydlyme, I will have mains power, I feel a low volume pump would be adequate as it simply needs to keep the mixture circulating. Any suggestions on a pump, Lidl, Aldi. Machine mart?
3. Would it be any benefit to use warm/hot water.
4. How long would you run the pump for?
Look forward to the forum comments
David MH
Click to expand...
Just about to circulate descaler through my DV24 (Wessex Proflush). Wondering if it is really necessary to remove the anode? Last time I checked the anode was a bit scaled too. Is it likely to magically melt in the descaler do you think?

Thanks
 
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