Johnson sea water pump leak

sarabande

sarabande

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A steady drip from the back of the pump on Yanmar 3cyl, so I took the whole assembly off yesterday. It's marked as an F4B 903 and the Johnson site refers to this model as a flange mounted pump, whereas mine is definitely a belt-driven one.

The part reference guide seems to identify the F4B -9 as being obsolete, which is a bit uncomforting. Additionally some parts of the sailing web seems to be less than delighted with the repair kits, citing recurrent leaks.

I believe the leak to be coming from the seal at the back, but as the engine has only done about 250 hours, I am wondering about changing to a Jabsco with a Speedseal.


Any views/advice on refurbing the Johnson, or changing to Jabsco, please ?
 
It's easy enough to put a new seal on a Johnson or Jabsco pump. You don't have to use official parts but can get them from any bearing stockist using the id marks off the old one. Make sure the new one has a stainless spring or it'll rot to nothing very quickly.
If your pump is difficult to access, a Speedseal conversion is worthwhile.
 
sarabande said:
A steady drip from the back of the pump on Yanmar 3cyl, so I took the whole assembly off yesterday. It's marked as an F4B 903 and the Johnson site refers to this model as a flange mounted pump, whereas mine is definitely a belt-driven one.

The part reference guide seems to identify the F4B -9 as being obsolete, which is a bit uncomforting. Additionally some parts of the sailing web seems to be less than delighted with the repair kits, citing recurrent leaks.

I believe the leak to be coming from the seal at the back, but as the engine has only done about 250 hours, I am wondering about changing to a Jabsco with a Speedseal.


Any views/advice on refurbing the Johnson, or changing to Jabsco, please ?
Click to expand...

If that's a YM series engine, my 3YM30s have a Johnson clockwise rotation F4B-903 / Part 128990-42500.

I've had no problem with obtaining parts for this model and have also fitted a Speedseal Life.

I can see no advantage in changing the pump.

Richard
 
As others have said, parts are available widely. When the seal failed on my Johnson pump on a 3GM30F, I replaced it with a Volvo one that has a stainless spring instead of the brass one on the Yanmar. I have bought spare seals, impellers etc from Marine-power, who carry a stock of them. Last season I had new seals and bearings installed in it in Greece (I could not press the old bearings out) and bought a new pump as a spare, perfectly straightforward.
 
Some feedback on Marine Power and ASAP

Out of 7 parts I want to replace/renew, Marine Power have 6, and the last one, a polycarbonate seal, is due in 10 working days time.

ASAP were not really any better, with both O rings on back order expected in a week.


I ended up after two hours chasing round on the doggan bone, with Aquafax 01 582568 700, who have all the parts, and they are in th epost :) And just over a fiver difference between all three. FWIW.
 
Having taken the pump to pieces, I've found the culprit. :)

The water seal between the back of the impeller and the pulley had a garter spring which has corroded to ions.

DSC_07541_zps1ppmzniy.jpg


Clearly, it was ordinary steel, but the new one will be stainless.

Disappointingly the recorded engine hours since new are 255 only, but something like 9 years since the new engine went in, during which time there will have been many thousands of hours when the spring was static in salt water in a complicated soup of bronze, stainless, and mild steel. It's a wonder it has survived so long, I suppose.
 
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