Refurbing a raw water pump - which way round do the lip seals go?

[Tarka1]

I'm in the process of refurbing an old Jabsco pump and have got to the stage where I need fit the new seals. The trouble is I can't remember which way round they go. They are lip seals with the circular spring pressing the seal on to the shaft. When refitting the seal next to the impellor should the spring be on the impellor side (wet) or the other way round?
Hope this makes sense.....

 

[neale]

When I changed one recently the seal went in spring to water.

 

[vyv_cox]

Think first principles. The seal prevents water at pressure from leaking out. Pressure inside the seal forces the lip outwards to make the seal. If the pressure was on the non-spring side it would force the lip inwards = leak. So the spring goes inside the high pressure side, i.e. in the water.

Usually the outer seal goes the same way, so that if water passes the inboard one when it has worn or been damaged, the leaking water comes through the vent hole in the casing. If the pump is mounted on the crankcase with its inner end driven by the camshaft, the outer pump seal is intended to prevent leaking water from getting in the oil. Make sure that the seals are fitted such that the vent is clear.

 

[scottie]

Usually the outer seal goes the same way
Dont think so more!!
likely one is to stop oil leaking out to telltail hole and the other is to stop water going the other way

 

[jerryat]

[ QUOTE ]
Usually the outer seal goes the same way
Dont think so more!!
likely one is to stop oil leaking out to telltail hole and the other is to stop water going the other way

[/ QUOTE ]

I agree. I have always fitted them 'back to back' for exactly the reason you state. It is the correct way. One 'faces' the oil, the other 'faces' the water. If either fail, the tell tail hole indicates which has failed.

 

[Tarka1]

Thanks everyone - I've now found instructions on the Jabsco site which confirm that the lip should face the impeller.

 

[Avocet]

If you didn't buy genuine lip seals, make sure you got ones with either stainless or bronze garter sprngs inside the lips.

 

[vyv_cox]

There's no pressure on the oil side (well, not in my crankcase) The outer seal, as I said, prevents water from going into the oil.

I know of a number of Bukhs that have seized due to water passing both seals and getting into the crankcase. The Bukh installed on my boat when I bought it leaked considerable volumes through the bleed vent and quite a bit into the oil. The outer seal was fitted with the spring to the oil side, where it was doing nearly nothing to stop the water flow.

 

[jerryat]

Well my Bukh manual clearly shows the lip seal facing the oil on one side and the raw water on the other! This is for the standard Johnson pumps that are fitted.

Have always installed them this way (as advised also by Bukh) and never had a problem. Whatever the condition of the engine, there is always a slight crankcase pressure, alleviated to some extent on Bukh engines by the inclusion of a vacuum valve.

Incidentally, and with reference to another poster, a terrific tip given to me some years ago by a chap at BSS was to remove the usual ms spring and replace it with an 'O' ring. Indeed when we were buying spare water pump seals prior to shoving off cruising a few years ago, they actually fitted the 'O' rings for me there and then!

The chap also pointed out that if you were 'caught short' with a leaking seal and no spares, 'simply' remove the offending seal, fit a slightly smaller 'O' ring and replace the seal. It was only a temporary 'get you home' fix, but it DOES work because I used this method on a friend's boat when we had a weeping pump in Brittany. Worked beautifully!