Water pump shaft seal = maintenance item ?

RobbieW

RobbieW

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Specifically the shaft seals on engine raw water pumps. I have learned, the hard way, that simply ignoring these can be expensive - especially when the pump is buried inside a casing. So what do you do to ensure maximum life from the seal and how often do you do it ?
 
There's nothing you can do to maintain the seals. You should check for leakage by observing the weep hole in the pump casing. If you spot or feel water from the hole, check the shaft for wear and replace the rubber seals. If the shaft is worn, replace the shaft as well or the seals won't work for long.
I'm struggling to remove my Johnson pump at the moment (flange mounted) due to difficult access so can't check them at the moment.
 
ghostlymoron said:
There's nothing you can do to maintain the seals. You should check for leakage by observing the weep hole in the pump casing. If you spot or feel water from the hole, check the shaft for wear and replace the rubber seals. If the shaft is worn, replace the shaft as well or the seals won't work for long.
I'm struggling to remove my Johnson pump at the moment (flange mounted) due to difficult access so can't check them at the moment.
Click to expand...

Not as straight forward as that.
Part of my daily engine checks are to feel underneath the pump for dampness or drips. Ours - even at 20 years old (Volvo/Jabsco) was fine.

BUT

On a motor from One port to another - with a rising gale forecast - the temperature started rising on the water. On looking - water was coming out from the vent underneath the pump at high pressure.

We continued at reduced revs - the engine cooling was ok - and less water spewed out, but it was still at the rate of about 10 litres every 5 minutes, requiring constant hand pumping of the engine bilge to prevent salt water entering the rest of the boat.

Once in the new harbour, we changed the pump, which I had luckily bought as a full working replacement a couple of days before!

The change over took 20 minutes - but circlip pliers were required - kindly loaned by the boat next door.

Cause of the problem: There is a plate at the back of the pump impeller housing that is located by a lug to keep it in place. This lug had disappeared and the plate was spinning freely. Quite how this damaged the lip seal so badly, I don't know as it could not touch it.

So be warned - just check for drips is not a sure check.
 
A cause of premature failure of water pump seals is back pressure. Various causes including debris in the heat exchanger on indirectly cooled engines and salting up of the injection point into the engine on raw water cooled, a particular problem with Bukhs. An additional problem is that the lip of the seal may press hard into the shaft, wearing a groove in it. Occasional checking for good flow into the engine is worthwhile. With a raw water cooled engine the flow may be good before the thermostat opens when the water goes through the bypass but poor later on when the engine is warm.
 
RobbieW said:
Specifically the shaft seals on engine raw water pumps. I have learned, the hard way, that simply ignoring these can be expensive - especially when the pump is buried inside a casing. So what do you do to ensure maximum life from the seal and how often do you do it ?
Click to expand...

I was told years ago by a VP main dealer in Pwllheli to take out the impellor, get a cotton bud and clean out the lips of the seal then fill with VP blue grease used in the prop shaft Volvo Seals. It works for me. Never changed one in either of my Benes.
S
 
vyv_cox said:
A cause of premature failure of water pump seals is back pressure. Various causes including debris in the heat exchanger on indirectly cooled engines and salting up of the injection point into the engine on raw water cooled, a particular problem with Bukhs. An additional problem is that the lip of the seal may press hard into the shaft, wearing a groove in it. Occasional checking for good flow into the engine is worthwhile. With a raw water cooled engine the flow may be good before the thermostat opens when the water goes through the bypass but poor later on when the engine is warm.
Click to expand...

Thanks Vyv; my installation is a genset that has an external water cooled inverter. There are several metres of tubing feeding cooling water around until it exits through the genset motor; I suspect that contributes to a higher than usual back pressure in this system.
 
skipper_stu said:
I was told years ago by a VP main dealer in Pwllheli to take out the impellor, get a cotton bud and clean out the lips of the seal then fill with VP blue grease used in the prop shaft Volvo Seals. It works for me. Never changed one in either of my Benes.
S
Click to expand...

Thanks for the tip; I'm guessing that any waterproof grease (thats compatible with the seal material) would help, given I have no other use for VP Blue on the boat :)
 
I certainly agree that the raw-water pump seal (and bearings) are a planned maintenance issue.

I understand that I'm unbelievably lucky in having had engines designed for marine use, so it's about a 4'-10' job to change raw-water pumps on all the Yanmars I've owned.

So I always carry a spare which has been fully overhauled and swap the pumps rather than groping to change impellers or be swinged by those who produce proprietary faceplates.

My experience with the Johnson pump is that an impeller does 400-600 hours and the seal (and probably the bearing) about 800 hours. With the Jabsco, impellers lasted half the time but bearings and seals were similar. Bearing, spacer and seal kit cost about £16 from the local Johnson agent, impellers about the same - price for the new pump was £169 with another £56 demanded by Yanmar for their apology for a pulley. I was able to buy SKF alternative bearings and seals in Crete for about €12. Only trouble the seal spring was not stainless steel.

So I don't change the impeller in situ - I take off the raw water pump and fully re-condition it and keep it in reserve for the next time.
 
You should be so lucky. I've been trying to get my pump off for 2 days now and its still not shifted. Cant get a socket on it nor a decent spanner. Most inaccessible, I doubt if it has been off since the boat was built in 1971.I can change the impeller with difficulty in about 30min. So the option of a quick switch of pumps is not an option for me.
charles_reed said:
I certainly agree that the raw-water pump seal (and bearings) are a planned maintenance issue.

I understand that I'm unbelievably lucky in having had engines designed for marine use, so it's about a 4'-10' job to change raw-water pumps on all the Yanmars I've owned.

So I always carry a spare which has been fully overhauled and swap the pumps rather than groping to change impellers or be swinged by those who produce proprietary faceplates.

My experience with the Johnson pump is that an impeller does 400-600 hours and the seal (and probably the bearing) about 800 hours. With the Jabsco, impellers lasted half the time but bearings and seals were similar. Bearing, spacer and seal kit cost about £16 from the local Johnson agent, impellers about the same - price for the new pump was £169 with another £56 demanded by Yanmar for their apology for a pulley. I was able to buy SKF alternative bearings and seals in Crete for about €12. Only trouble the seal spring was not stainless steel.

So I don't change the impeller in situ - I take off the raw water pump and fully re-condition it and keep it in reserve for the next time.
Click to expand...
 
I have had two pump failures (water leak from tell tale hole) in 8 years. Both cases were because the tiny circular spring on the shaft seal had rotted, even though they are supposed to be S/S. I can only think that the small diameter wire this shaft seal spring is made from is not really fit for long immersion in salt water. The trick of applying water pump grease to the shaft seal spring must help slow the corrosion. I can't remember where I read it, but isn't it possible to remove the seal spring and replace it with an "O" ring of the correct dimensions?
 
ksutton said:
I have had two pump failures (water leak from tell tale hole) in 8 years. Both cases were because the tiny circular spring on the shaft seal had rotted, even though they are supposed to be S/S. I can only think that the small diameter wire this shaft seal spring is made from is not really fit for long immersion in salt water. The trick of applying water pump grease to the shaft seal spring must help slow the corrosion. I can't remember where I read it, but isn't it possible to remove the seal spring and replace it with an "O" ring of the correct dimensions?
Click to expand...

Yet mine lasted 20 years and 4000 hours..... Perhaps as you say the modern lip seal is substandard - better watch out on my new pump!
 
ksutton said:
I have had two pump failures (water leak from tell tale hole) in 8 years. Both cases were because the tiny circular spring on the shaft seal had rotted, even though they are supposed to be S/S. I can only think that the small diameter wire this shaft seal spring is made from is not really fit for long immersion in salt water. The trick of applying water pump grease to the shaft seal spring must help slow the corrosion. I can't remember where I read it, but isn't it possible to remove the seal spring and replace it with an "O" ring of the correct dimensions?
Click to expand...

When ever I replace any lip seal on my boat I remove the spring from the new seal and test it with a magnet. If it sticks I take the old seal spring and fit it to the new seal.

Interesting point about using and O-ring must remember that.

You can always specify a seal with a stainless steel or copper spring at some seal suppliers.
 
Rogershaw said:
When ever I replace any lip seal on my boat I remove the spring from the new seal and test it with a magnet. If it sticks I take the old seal spring and fit it to the new seal.

Interesting point about using and O-ring must remember that.

You can always specify a seal with a stainless steel or copper spring at some seal suppliers.
Click to expand...

This is one case in which it is worth buying Volvo rather than Yanmar. The spring in the Yanmar seal for 1/2 inch shafts is a copper alloy, the seal in the Volvo equivalent has exactly the same dimensions but the spring is stainless steel that lasts a lot longer. Marine Power will sell you one with a stainless steel spring at a third of the price of a Volvo one, so the best of both worlds.
 
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