MD21B Raw water shaft pump seals

Ariadne

Ariadne

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The Mrs kids and boat are in Grenada. Me? I'm in S
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I think the VP part number is 827247, but can anybody please tell me sizes of the seal? I know I can get the numbers off the existing seals, but as I'm at anchor I don't want to rip the seals out and not be able to replace them immediately just in case we need to move sharpish. I know I should have a spare set onboard, I do but I can't find them!

Another question for the engineers, I had new shafts made, the faces skimmed and fitted new bushes, basically rebuilt the pump. Why has the inner seal collapsed after 275 hours, or is that about right for the seals life? Should I be looking at replacing them at 200 hours or do I have another problem?

Cheers all
 
Ariadne said:
Right, I'll go and look for S/S seals then. They should last longer then 270 hours at a guess?

Could this be why the VP original parts cost quite a bit more, they have S/S springs? The the ones I'm bought in the hydraulic shop, were only €3.00 each!
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The VP ones may have S/S springs, or they may just be higher spec. It wouldn't be unreasonable to expect seals on an average boat pump to last for nearer 1000 hours. You may have difficulty sourcing seals locally with S/S springs, in which case it's probably better to go for a decent brand rather than a cheap & cheerful anonymous item. Do you perhaps think the finish on the new shaft wasn't right?
 
The small Yanmar water pump seals (12 mm) have brass or bronze springs. Mine failed in Nidri, where I was adised that Volvo ones are exactly the same size but have stainless springs. Marine Power stock some others, stainless steel springs but much cheaper than the Volvo ones.
 
I've been following up on the same size seal for the raw water pump on a Nanni 4.150. The actual pump is a Johnson F5B-9000 series pump which seems a common usage item, espeially on Volvos. I found a link on the Moody owners forum, http://www.moa.myzen.co.uk/discus/messages/5/26308.html?1353276275, where they dont believe that an SS spring is viable but had had good results replacing the spring with a suitable O ring. It also has a link into the RS site which will also deliver 16x28x7 seals

Edit - mines gone at c.1000 hrs, it looks as if the old seal had a bronze spring (or a rusty mild one)
 
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Do you still have the original seal, if so retrieve the spring and test it with a magnet (stainless and bronze springs are not magnetic) you could also test the spring from a local supplier in the same way.
 
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