Engine Advice - Bukh DV 10

[spiller]

Briefly, just had the head off to replace a bent pushrod (valve seized in seat). Successful repair. However, the thermostat housing was found to be very corroded to the extent that the bolt holes had been eaten into.

All works fine except that the water pump does not prime itself but a short oral "suck" on this gets it going!

I think this is caused by the porosity of the thermostat housing which allows the water to drain back through the pump????

Made contact with Norman at Bukh in Poole, but they are closed until Jan 10.

Any opinion/advice on the following would be gratefully received:-

I plan to clean up the thermostat housing (acid solution?) and fill the corrosion enough to re-isolate the bolt holes, which should/might eliminate the air ingress and hopefully maintain a head of water.

There are "epoxy/metal" fillers available which should do the job. Any recommendations?

On the other hand, it may be nothing to do with the above, but the impeller is new, the pump is recent and both worked perfectly prior to the recent problem!!????

 

[Poignard]

Devcon

When I was an engineer in the MN a product called Devcon was always carried on board for emergency repairs to castings etc.

http://www.itw-devcon.co.uk/

You could ring their technical department and seek advice as to which of their current product range would be best.

Other companies probably make equivalent products but Devcon seemed to be the one most favoured at that time.

 

[chewi]

Surely a priming problem is an air leak either at or upstream of the water pump?
It can't be downstream of the pump unless its blocked, and if so it wouldn't respond to the help you give it.

Check your hose and check the faceplate seals against the impeller. eg clean off the face gasket and refit. use a straight edge and feelers across the pump body to ensure no leakage clearance.

 

[neil_s]

Also check the pump shaft bearing - wobble in the shaft knocks out the seals and lets air into the pump, as well as water into the chain case!

Neil

 

[neil_s]

Also check the pump shaft bearing - wobble in the shaft knocks out the seals and lets air into the pump, as well as water into the chain case!

Neil

 

[Bilgediver]

porosity in thermostat housing which allows the water to drain back through the pump????

As the water system itself is open to atmosphere at the exhaust end any way an airleak at the thermostat housing is of no consequence . It is not unusual for pumps to be behaving perfectly then after a wee overhaul fail to prime.

It is more likely to be a worn casing , worn back plate or old impeller. It will be a good idea to Devcon the casing however I doubt this will affect the problem you reported.

 

[Poignard]

It will be a good idea to Devcon the casing however I doubt this will affect the problem you reported.

Yes that's quite right.

I didn't mean to suggest that repairing the casting would solve the pump priming problem. That's a seperate issue.

The pump should self-prime and pump water even if there is nothing at all connected to its outlet.

An overhaul of the pump would be a good idea; including shaft seal renewal because if water creeps along the driveshaft and into the engine you may end up with a bigger bill!

 

[boatmike]

Briefly, just had the head off to replace a bent pushrod (valve seized in seat). Successful repair. However, the thermostat housing was found to be very corroded to the extent that the bolt holes had been eaten into.

All works fine except that the water pump does not prime itself but a short oral "suck" on this gets it going!

I think this is caused by the porosity of the thermostat housing which allows the water to drain back through the pump????

Made contact with Norman at Bukh in Poole, but they are closed until Jan 10.

Any opinion/advice on the following would be gratefully received:-

I plan to clean up the thermostat housing (acid solution?) and fill the corrosion enough to re-isolate the bolt holes, which should/might eliminate the air ingress and hopefully maintain a head of water.

There are "epoxy/metal" fillers available which should do the job. Any recommendations?

On the other hand, it may be nothing to do with the above, but the impeller is new, the pump is recent and both worked perfectly prior to the recent problem!!????

I agree with others that the problem is probably upstream. With a good installation the engine pump should self prime, but if the pipe run is not good or there is a leak in that (do you have a filter or anything else that could leak between the seacock and engine letting air in?) you could be sucking air or there could be an airlock. If the thermostat housing were leaking it would show up as water coming out under pressure when running not air getting in surely?

 

[SimonJ]

BUKH 10 issues

Both your problems are fairly common with BUKH's unfortunately.
The thermostat bodies do corrode over the years; you may be able to do a temporary short term fix with some form of chemical metal (it has worked for me) but a replacement will be needed fairly soon. BUKH will supply correct length bolts, gasket and housing. Raw (salt) water cooling inevitably brings on heavy corrosion eventually. The block anode may not have been replaced as often as needed. Worth checking now.
Pump effectiveness degrades mostly because the surface plate wears. It is possible to 'rub out' the wear marks using various decreasingly finer grades of emery then crocus paper etc. The right thickness joint is also important. As commented elsewhere shaft wear can also occur. If you need to replace any part of the pump better to fit a good, complete replacement. A better pump that fits is the bearing type as used on the BUKH 24 (& other engines); GOOGLE around a bit and you will find a replacement for about £100 (but more expensive from BUKH Poole!) . These pumps are not then susceptible to the other classic BUKH 10/20 fault of allowing water to get to the sump via undetected failed seals and all that that entails. So, well worth fitting the BUKH 24 pump. Possibly with a stuck valve, water ingress might have happened in the past?

 

[footsoldier]

There are "epoxy/metal" fillers available which should do the job. Any recommendations?

There is a good American product "J B Weld" which is resistant to pressure/heat/oil etc., - they claim it can even be used to repair cylinder blocks - and it has been highly recommended on here in the past. It's available on-line, - think I got mine from an EBay shop.

 

[Mistroma]

I've used JB Weld and it performed very well.

I had a similar problem with my old DV20 and believe that air was coming in through the pump seal. I think that the pump failed to prime because of wear on the inner surface behind the impeller.

I seem to remember that there was a firm offering to machine the relevant parts flat again. However, I fixed the problem by polishing as mentioned previously (wear wasn't too bad). I replaced the seals as well (& kept spares as they were cheap when purcahsed from BSL).

I saw someone mention that getting water from the pump into oil was a common fault on DV20. Actually, the pump on my DV20 (circa 1980) had 2 seals (water & oil) on the shaft. The tube covering the shaft had several Judas holes in it. If either seal leaked then water or oil dripped out. Check that these holes have not been covered in paint. As long as they are open you will get plenty of warning if either seal fails.

I picked up some spare parts a few years ago from my local boatyard. They had a DV20 and a DV10 lying around. If you are interested, I could drop in and see if they are still sitting there. However, they might be closed for Hols. soon so it could take a while.