Seawater Pump Leak - D1-30

[Sootydog]

Last year I had a water leak from the rear of the seawater pump assembly on a D1-30 engine.

It was traced to the sealing ring behind the impeller (rubber seal fitted with steel spring like retainer).

The seal was changed and all was fine.

This year, it has started leaking again, not excessively but enough to be annoying.  What am I doing wrong or is this to be expected?  I have a spare that I will fit at the winter haul out but I want to get it right this time.

[Yngmar]

Did you inspect the shaft? The shafts tend to wear where the seal rides on them, and once they do, the seal won't seal no more. You can either replace the shaft, sleeve it or sometimes seat the seal differently so it rides on a different part of the shaft.

Example picture from image search: http://avtokomtg.com/images/articles/iznos_vala_nasosa/iznos-vala-nasosa.jpg

[Sootydog]

Yngmar,
            The shaft showed little sign of wear.  I was thinking that the seal may have "dried" over last winter.  Should some sort of lubricant be needed?  From memory the seal was quite a tight fit and i pressed it home using a long socket.  It was sealing fine for a whole season then failed early this season.
If I've got this right, there is a spinning shaft trying to seal onto a rubber seal with only water as a lubricant. Or am I missing something?

[Salty]

Yngmar,
...... It was sealing fine for a whole season then failed early this season.
....................or am I missing something?

Possibly, ........what sort of quantity of water are you talking about ?

I had a a similarly leaking water pump, though while it didn't seem to be leaking very much, the quantity of water I had to pump out suggested a fairly significant leak. Nevertheless I replaced the seal on it, but while that cured the pump leak, it didn't stop the water I had to pump out. Looking further revealed that the Volvo silencer stainless steel endplate had corroded through, and was leaking raw cooling water into the bilge. It was a new silencer that actually fixed the leak.

[Sootydog]

Salty,
   I can see the water dripping from the general area of the pump.   I would estimate about a cup full every hour - max.  Looks exactly like the last time it was leaking.  I was hoping it was a duff gasket on the impeller cover, but checked, and no.