BUKH DV20 WATER PUMP

[alan54j]

after 18mths on the hard we returned our boat to the water. the raw water pump wont work, new impellar .. no difference. it seemed to work a week before launch with using the filter but after priming no joy..
our conclusion is the impellar housing is worn !
anybody got any other suggestions ?
thanks

 

[jerryat]

Asssuming the drive chain isn't broken i.e. the pump shaft is turning the impeller, then I suspect that you are right, and that the face plate has worn enough prevent proper priming and function.

If so, this might be the time to switch to a Speedseal, as I did a couple of years ago and have been very pleased with.

The other (unlikely) possibility is that the metal insert in the impeller has detached from the impeller itself and is just turning. Easy enough to check by removing the face plate and tuning the engine over.

Please let us know what the final solution is.

 

[Poignard]

First thing is to determine if the problem is with the plumbing, the pump or the drive to the pump.

Things to check are:-

Seacock open[!]
Inlet strainer clear
Pipework not blocked
No air leaks in suction side
Impellor ok and still bonded to its bronze sleeve
Cross screw that transmits drive from shaft to impellor ok
Is the impellor being turned by the engine ?[turn engine over with cover removed to see it]

A fairly common problem with these engines is that the pump seals have failed, allowing water to pass along the shaft into the engine chain case and corrode the steel cross pin that transmits the drive to the pump shaft. That eventually corrodes through and you lose drive to the pump. Clues that this might have occurred would be water leaking out around the pump body and getting sprayed around by the flywheel.

ps the front covers do, of course, wear but it can't have worn any more whilst the boat was laid up and you say it was working when laid up.

 

[James_Calvert]

Is the inside of the face plate worn? If so, try replacing it back to front - it worked for me.

 

[nightjar]

Check the cam for wear by removing the impellor. The cam should have a "polished" surface all across its face where the impellor has been in contact. Look for any dull areas which demonstrate poor contact as a result of cam wear. Cam is held in place by one screw and is easy to replace. Also worth reversing face plate if it shows wear.

 

[alan54j]

well chaps the solution was very simple. everybody was on the right lines, the impella was turning when hand cranked.
but after speaking to TW marine (bukh dealer ) a man thare called william who i have had dealings before discussed the problem with me over the mobile while on the engine
is the pump spindle worn and/or any play there was slight
is the front cover worn ! if so reverse the front cover after lightly vasaline everything. i reversed the cover primed the pump and tightened everything up and whala it poured water out of the exhaust. so the 50 quid i gave the local mechanic to solve the problem and he said get a new impella housing was money down the drain !!
thanks

 

[jerryat]

Glad it's all sorted and thanks for letting us know.

However, I've always been a bit puzzled by the recommendation to 'reverse the cover plate - except in an emergency situation. I can't remember whether it would be on the 'impeller contact area exactly, but I thought the plate was stamped with the makers name/type etc and would have thought this might have damaged the impeller.

Anyone tried the 'reverse plate' long term?

 

[PeterGibbs]

Worn face plate? - apply emery/power weel, not abrasive brush, to reduce ridging and enable impeller to prime. There is enough metal there for this to be done several times in the life of the plate.

Check impeller blades all there and still have their rounded ends intact. Any defects - replace.

Check water passthrough by detatching output end of pump and starting engine (run only a few secords to prove the system)

Water issuing from back of pump? The seal in the back of the pump needs replacing.

Whilst working on the pump housing, check the circlip in the middle of the drive shaft. It is there to throw off any water moving inwards from the pump towards the engine. If water passes this point it will enter the oil system and do damage bigtime! Replace circlip - you will need reverse pliers to do this (jaws open out as you squeeze) Rusty circlip says water is loose in the area!

Bukh water pumps need a little more attention than other types but are simple, hardworking, open to quick inspection to ensure proper working, and problems easy to rectify.

PWG

 

[peasea]

If you replace the pump shaft seals be sure to fit Bukh original seals because they are fitted with phos. bronze springs.Any other will soon break down and seawater can enter the sump. The circlip thrower is a must.
Make sure that all the impellor vanes are facing the right way in the housing by turning the engine over by the starting handle with the front cover of the pump removed.

peasea

 

[James_Calvert]

Worked for me for several years now. Impellor undamaged. Can't read too much of the stamped lettering any more. Only issue is that I've not got a quick fix when that side of the faceplate gets too worn as well. I gather that Bukh UK will supply a new plate (can't remember the price) for the pump so I really ought to get a spare one, or reface the old working surface as PeterGibbs suggests.