Rebuilding Bukh DV24 raw water pump, again!

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cat007

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Hey all

It's coming up on summer here in New Zealand and when doing my pre-summer checks I've noticed my engines raw water pump is leaking water quite badly.

This is about the 3rd time it's done it - maybe 4th even.

Last time I replaced the shaft for fear it was worn and chewing out the seals - this time I'm not sure why this is happening. Perhaps the seals I'm using aren't up to scratch? I've been buying the pairs of seals and bearings (sealed bearings) from a local bearing distributer.

I have been put off for buying them from my local marine engine supplier as they are, no kidding, 4 times the price....

Has anyone else had issues with their Bukh's raw water pump causing constant rebuilds? Perhaps my brass housing is warped somehow?

I really don't want to spend the $13 per seal and $30 per bearing, only to have it fail again in a couple of months....
 
Make sure that the springs in the seals are 316 stainless or the salt water will take them out pretty quickly. You should be able to get them from bearing suppliers.
 
rhumlady said:
Make sure that the springs in the seals are 316 stainless or the salt water will take them out pretty quickly. You should be able to get them from bearing suppliers.
Click to expand...

Thanks for that. I will double check that the springs are 316SS.

If the water gets past the seals, shouldn't the sealed bearings stop the water too? And although they're sealed bearings, is there a chance that salt water will get inside them? I noticed the shaft is quite stiff to turn even without the impeller on the end.
 
cat007 said:
Thanks for that. I will double check that the springs are 316SS.
If the water gets past the seals, shouldn't the sealed bearings stop the water too?
Click to expand...
No
cat007 said:
And although they're sealed bearings, is there a chance that salt water will get inside them?
Click to expand...
Yes
cat007 said:
I noticed the shaft is quite stiff to turn even without the impeller on the end.
Click to expand...
Knackered bearings?
 
Yeah - I thought the bearings wouldn't allow water into them - but yeah if they do then it makes sense that the bearings a shot.

Just to confirm - the spring on the seals should face the liquid being sealed? i.e. the spring side towards the water and on the other one, the spring side towards the engine oil?
 
cat007 said:
Yeah - I thought the bearings wouldn't allow water into them - but yeah if they do then it makes sense that the bearings a shot.

Just to confirm - the spring on the seals should face the liquid being sealed? i.e. the spring side towards the water and on the other one, the spring side towards the engine oil?
Click to expand...
Yep, you got it in one.
 
Ok so I've just taken my pump apart.

The stainless shaft that I made from what I thought was "good quality" stainless - is totally destroyed. The RUBBER seals have eaten away at it to the point that in some parts it's just over 1mm smaller than the rest. So I guess it wasn't as good quality as I thought....

Guess that's why it was leaking like a sieve.

Now I'm tossing up whether I buy an OEM part for +$75 - or make another shaft from (hopefully) better sourced stainless bar....
 
Perhaps the worst situation for lip seals is high back-pressure, which causes them to do exactly what yours has. OK, your shaft material may not have quite been up to the job but it is probably not a million miles different in surface hardness than the genuine article. The water injection point on a Bukh, hidden behind the flywheel, needs regular cleaning to clear the salt encrustations that progressively block the holes in it. When these block the pressure developed by the pump is enough to destroy seals in short order.
 
Thanks for that. I'll take the flange off where the water feed goes into the block and make sure it's clean and unobstructed. Could be a blockage as you suggest.

I plan on doing a decent flush using a bilge pump a my power source.

I was going to do what I've done before, fresh water flush for about half an hour, recirculate white vinegar for about an hour, fresh water flush for 10 minutes, white vinegar for another half hour then fresh water rinse for another 10 minutes. From what I've read this is a pretty good flushing/cleaning solution....??

Cheers
Hunt
 
Hi all,

So my water pump issues are back again, this time with a vengeance - I haven't even used it yet!

Anyway - I thought before firing the engine up I'll turn it over by hand and make sure the water pump is turning etc - lucky I checked as the shaft of the pump wasn't turning.

I took the pump out and noticed the water pump drive had wear marks on it - as it the water pump shaft wasn't able to turn, whilst the drive on the engine side was - wearing groves in the drive.

The only way I can think of this to happen is from a pump shaft that's slightly too short and not coming in enough contact with the drive. I can't understand how this could be as the shaft is OEM and the pump was snuggly bolted up to the drive housing. There is no excessive wear on the front plate.

Perhaps something has happened on the engine side, causing the drive to be recessed back slightly? Is the drive serviceable? Specifically if I wanted to replace the drive that the shaft is powered off?

I was thinking an easy way to 'fix' it, would be to make another shaft that's 5-10mm longer so it slots into the drive....
 
Hi - thanks for the reply

No the pin on the new impeller is fine - it's the pump shaft that's not turning. I don't have any pics sorry.

Extracted this from the workshop manual - it appears that part 20, a small pin, is what has has worn due to the shaft (for some reason) not being slotted into the drive housing as far as it should.

It looks like a total p.i.t.a. to get to and replace?

 
You say the shaft is original genuine bukh, then say you machined it yourself, or did you finally buy a bukh one ? You find they are all tucked up in bed in UK at this time. So does pin 20 rotate?
 
Hey

Yeah I tried the original, unmolested bukh shaft and measured the amount it needs to stick out of the back of the pump housing so it has full contact with pin 20, and it appears to be a few mm too short. I thought I had the shaft around the wrong way. The slots in the shaft are different depths and thicknesses. I assumed the shorter slot went to pin 20 and the deeper but narrower slot to the impeller?

Yeah pin 20 rotates fine. There is a very small amount of in and out movement of the assembly/gear thing that pin 20 is attached to, but it's only about 1mm....
 
I've taken the whole 'raised hand start' housing off the engine and am trying to remove pin 20 which appears be held in place by the inner race of the bearing (part number 24). I'm guessing as this is a bearing race, it's most likely pressed on? There is a little wear on the inner race, so it probably needs replacing anyway.
 
Part number 24 is called the "lnner collar", LR 20x25x12.5
Part number 24A is a Needle Bush (roller), IK 2512
 
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