Just so if any one thinks of fitting a VDO temp gage to there Buhk Diesel with a twin terminal sender you will have a failure problem as for some reason
( depth this can be over come with a spacer ) but ever after making a space they will still fail. Even a Buhk spares seller in the UK told me this when I was researching the sender. What some of the local Walker H28s have done is fit a signal terminal VDO sender in the Buhk engine drain and have no problems since and keeping the original bulk sender ( warning light)in the thermostat housing
Some useless information for Loose Change to store away in his brain archive 
winking at you loose change
At around $80 each its good advice
the Buhk engine block drain thread is 14 mm so buy a 14 mm sender signal terminal not the one below
Select to expand quoteandy59 said..
I'll be doing that HG thanks for the tip
Ill get the part number and put it up if you or any one else have a bukh on board MMMMMMMM sounds like a rooster bukh bukh bukh Brizzy Dave would be interested in that
The signal terminal sensor is around the $30 mark
I use this VDO sensor on my Bukh DV10-LSME and it works fine, it has dual terminals;
Select to expand quotekeensailor said..
I use this VDO sensor on my Bukh DV10-LSME and it works fine, it has dual terminals;
I have the same sender here as your part number its just other walker owners (DV 20)have had trouble with it not working after a short time . A friend of mine has tried three so far all have failed . He used a spacer to keep the depth shallow but still had trouble and made sure there was clearance .
I inquired in the UK about this sensor and was told by the Bukh spares part seller they also had trouble . He said they wont last. All these were fitted in a Bukh DV 20.
I wonder if there's a different part number for the DV 10 Thermostat housing than the DV 20. Ill check my spare parts book see what I can find of there is a difference
You would have a different thermostat housing than the DV 20 Ids say I have not removed the housing yet been to busy but might try this week see what I can work out .
Its some thing to do with the combination of the thermostat housing and the sensor I feel on the DV 20.
You cant just screw the sensor in to the DV 20 you have to use a 12 to 14 mm spacer to give it clearance that's all I know at the moment .
I have been through a number of these on a Bukh DV20in an H28. It appears that the tube making up the sender splits along the solder join that runs the length of the brass probe. I have established that is not due to a tight fit or bottoming out but believe it may be electrolytic.
Nevertheless the sender can be repaired by placing it fresh water for a few days then drying it with a heat gun. If you use hot water you can see the split - air bubbles come out! I sweat solder over the split and give it a thin coat of expoxy paint. Usually good for a season.
The split and egress of sea water does not appear to effect the functioning of the alarm switch (96C) which in my case wired to the motor loom and alarm light but also to cockpit alarm light and buzzer.
However sea water does effect the thermistor output. Mine is wired to a VDO dial and when water starts to seep in the apparent temperature of the engine creeps up from normal (about 60C) eventually going off scale!
But as pointed out above they can be repaired and you can check the function using thermistor characteristic curves (Temp vs Resistance) on VDO web site using a multimeter and hot water. It amazes me that VDO are so silent about this as this appears to reasonably common problem if you look on the internet.
I am not professor on electrolysis but the first thing that came to mind ,paint the sensor with anti foul 
another comes to mind not sure if it would work heat shrink the probe < D,K, is no professor
Tried that and learnt by experience! If the thick paint or heat shrink comes of as a sheet it plays havoc with thermostat and down stream parts of the water cooling system.
Select to expand quoteJabberwock said..
Tried that and learnt by experience! If the thick paint or heat shrink comes of as a sheet it plays havoc with thermostat and down stream parts of the water cooling system.
That crossed my mind also mine raw water cool so its only the exhaust water and thermostat.
Thanks for the info thats why my senders still in the packet it came it.
Buit as I said other bukh owners have fitted a single terminal sender for the VDO gauge in the block drain and have had success
you just need a 14 mm single terminal sensor for the gauge
Jabberwock
I wonder what would happen if you made an earth wire off the side of the sender unit.
perhaps the senders are not earthing through there threaded surfaces to the thermostat housing( visualize the thermostat gasket as well as an insulator) and creating electrolysis problem.
I once saw an apprentice fitting a earth wire in an incorrect location on a Isusu truck while fitting a air condtioner causing massive eletrolisis in a mater of two weeks totally destroyed a new radiator in that time
The sender is earthed through the motor and the two terminals are for the alarm and temperature output. If the motor is not earthed or the sender is isolated (ie put in a plastic fitting or in a part of the rubber tubing) then it will not work unless you earthed as you suggested. I don't think that earthing the sender in any other way will make any difference to the electrolytic activity that is going on in the cooling system.
The electrolytic activity is pretty strong as I get through a pencil motor anode within 8-9 months! Warm sea water and a mixture of metals!
It is interesting that the Bukh replacement sender has a red paint coating on the probe (see below and www.frenchmarine.com/product/Bukh-552J0918-Temperature-Sender-2073-3). Also the price! Double what you pay in Oz for a sender from VDO. Suspect that Bukh have worked out that the probe needs protection!
Select to expand quoteJabberwock said..
The sender is earthed through the motor and the two terminals are for the alarm and temperature output. If the motor is not earthed or the sender is isolated (ie put in a plastic fitting or in a part of the rubber tubing) then it will not work unless you earthed as you suggested. I don't think that earthing the sender in any other way will make any difference to the electrolytic activity that is going on in the cooling system.
The electrolytic activity is pretty strong as I get through a pencil motor anode within 8-9 months! Warm sea water and a mixture of metals!
It is interesting that the Bukh replacement sender has a red paint coating on the probe (see below and www.frenchmarine.com/product/Bukh-552J0918-Temperature-Sender-2073-3). Also the price! Double what you pay in Oz for a sender from VDO. Suspect that Bukh have worked out that the probe needs protection!
WE are doing some high corrosive protection at work at the moment on a some machines, Ill ask a few question from a few companies we use .
In a previous post the person with a DV10 had no electrolysis problem with his twin terminal sensor.
It sounds like you hit the nail on the head. It would definitely be a ground issue when using that spacer. By attaching a ground wire between the washer and hex and running it to a good ground point should resolve any issues.
I received the above reply back from VDO today
I'm not sure if you are using a spacer between the Hex and the sender probe? But that what I will have to do fitting my VDO sensor as its to long.
I have it here so I might as well try it cant return it
But I still like the idea of some sort of electrolysis protection for the sender probe
I do not use a spacer. The sender is screwed into the thermostat housing. If you can get the housing off it is worth considering milling out the indentation for the sender so that your sender fits. That is what I did. There was already enough space but I took a little more off to make sure.
When I took delivery of the boat there was problems with the engine over heating. Found that it was the thermostat that had collapsed blocking the flow of cooling water. The thermostat was eaten away probably due to electrolysis since the pencil anode was completely missing! I routinely change the anode for new one every 6 months.
Select to expand quoteJabberwock said..
I do not use a spacer. The sender is screwed into the thermostat housing. If you can get the housing off it is worth considering milling out the indentation for the sender so that your sender fits. That is what I did. There was already enough space but I took a little more off to make sure.
When I took delivery of the boat there was problems with the engine over heating. Found that it was the thermostat that had collapsed blocking the flow of cooling water. The thermostat was eaten away probably due to electrolysis since the pencil anode was completely missing! I routinely change the anode for new one every 6 months.
Ill remove it a mill it down thats a good idea thought there might not be enough room to do thats I just have not removed the thermostat housing except when I first bought the boat and ran vinegar through it nearly 12 months ago.
Thanks for the tip Jabberwock
I ran my engine up today with forward thrust again the pier Im on was not real happy with the amount of water coming out the exhaust so I wanted to remove the thermostat tomorrow and test it so.
I have a 6 bolt flanged water pump and I want to buy the up graded 4 bolt which pumps more water volume .Mines a early Buhk around 1977 I guess
Ive also bought a speed seal kit to suit a four bolt water pump buit I also want to find out mre on the cooling pipes that enter the block as mine are a smaller diameter Maybe 10 mm pipe I believe the four bolt engines use 1/2 barbs plu the piping going to and from the block appear to be different than mine
www.speedseal.com/SpeedsealLife/SpeedsealLife.html
Jabberwock
I wanted to ask you about what you know of up grading my Bukh DV 20 water pump.
At the moment aI have a 6 bolt thrust flanged pump and Ive bought a speed seal kit for the motor and want to up grade the pump to at least the 4 bolt flanges pump . I have read you can fit the DV24 water pump which had roller bearings rather than the bushes which the DV20 has.
The other thing Id like to do is up grade the out let hose barb and also the inlet to the motor which also has the out let going to the thermostat housing to a larger hose size . Hopefully increasing the water flow out the exhaust which is pitiful on the 6 bolt flange pumps
Have you any ideas on that subject ?
My boat has a four screw Johnson pump (F35B-9) and it sounds likes yours has the older pump. I have no experience of changing pumps. However I have serviced mine - easy to remove. Part of routine maintenance replaced the bushes/oil seals and O-ring. If the DV 24 pump is a bolt on cannot see any problems. You can check detailed drawings on Johnson pump web site and compare them with your model. I have replaced all the tubing associated with the cooling system as a matter of routine maintenance and installed a Vetus syphon breaker. I have also been through the system and found scale build up in the Y tube (diverter) especially the part that goes into the block, the top of the thermostat where the by-pass water mixes with the water coming from the block through the thermostat and the injector into the exhaust. The latter two were really restricting the flow of water.
I was worried about the amount of water coming out of the cooling system especially on cool days when the exhaust has a tendency to steam. Using a bucket to catch the water coming out of the exhaust I measure a rate of about 8 litres/minute at three quarter max revs. Max output is quoted as 11 litres/minute at max revs. Seemed enough so I stopped worrying! Bukh's are also know to steam especially on cool days.
Looking back at our previous posts it is possible that your motor was older than mine. Mine was rebuilt in 2005. I noticed in the copy of the work shop manual I have for DV20 states that it is not possible to use a dual temperature sender as the older thermostat housing does not have enough space.
Select to expand quoteJabberwock said..
My boat has a four screw Johnson pump (F35B-9) and it sounds likes yours has the older pump. I have no experience of changing pumps. However I have serviced mine - easy to remove. Part of routine maintenance replaced the bushes/oil seals and O-ring. If the DV 24 pump is a bolt on cannot see any problems. You can check detailed drawings on Johnson pump web site and compare them with your model. I have replaced all the tubing associated with the cooling system as a matter of routine maintenance and installed a Vetus syphon breaker. I have also been through the system and found scale build up in the Y tube (diverter) especially the part that goes into the block, the top of the thermostat where the by-pass water mixes with the water coming from the block through the thermostat and the injector into the exhaust. The latter two were really restricting the flow of water.
I was worried about the amount of water coming out of the cooling system especially on cool days when the exhaust has a tendency to steam. Using a bucket to catch the water coming out of the exhaust I measure a rate of about 8 litres/minute at three quarter max revs. Max output is quoted as 11 litres/minute at max revs. Seemed enough so I stopped worrying! Bukh's are also know to steam especially on cool days.
Looking back at our previous posts it is possible that your motor was older than mine. Mine was rebuilt in 2005. I noticed in the copy of the work shop manual I have for DV20 states that it is not possible to use a dual temperature sender as the older thermostat housing does not have enough space.
When I ran my motor on Saturday I was not happy with the flow or the out put from the exhaust water. So Sunday I pulled the pump thrust plate off and looked around in the out let side of the pump in the barb hose piece I found it partial blocked by a piece of calcium restricting the flow. Once I tremoved this and reassembles I found much better water flow from the exhaust .( read some where 17 liters it ,may have been the DV24) .
The only thing that concerns me is the genuine Bukh water pump has bronze seals where as the Johnston one does not .
The difference between the DV24 pump is two main things the water volume is more plus it also runs two metric bearing not bronze bushes as in the DV20 pumps
I found a place in Australia that sells the Johnston pump $395 but not much info
www.google.com.au/search?q=F35B-9+-10-35157&client=ubuntu&hs=0RK&channel=fs&tbm=isch&tbo=u&source=univ&sa=X&ei=WcDhVNO-K9Po8AWm2IIw&ved=0CB4QsAQ&biw=2560&bih=913
The Y diverted that goes into the block also Id like to change out to a later model with bigger hose barbs . Ay some stage soon Ill collect all the parts I need and go through the cooling system and make sure every thing is clear and clean. After I find out a bit more info I think Ill buy a genuine Bukh DV24 piump and up grade my Y diverter pipe also .
So it looks like Ill have to find a late model thermostat housing to be able to fit the twin terminal temp sender.
