MD2B Water pump lip seal failure- again!

[Akestor]

It's a Johnson pump without bearings, the impeller shaft goes through the oil and water seals directly on the camshaft edge. The water seal lasted 90 hours only and luckily there is no oil contamination as i spotted the leak at the weep hole soon enough, and hope the oil seal is still ok. As i had another failure last spring with water getting into the crankcase i am checking the pump very often. I am sure i am installing the seals correctly but with the absence of bearing, it seems that all the shaft movement is loaded on the seals making them fail quickly.
I think this is a very weak link and the engine can fail when i need it...
-Would a new pump with a ball bearing holding the shaft last more hours before seals replacement?
-What about installing a belt-driven pump on the front of the engine? I would have peace of mind knowing that the sea won't get in the crankcase...

 

[VicS]

There are several pumps shown in the parts catalogue All have 2 ball bearings
The seals should be fitted with the spring sides facing away from each other
If the shaft is not running in bearings of some sort, only supported the seals, they are not going to last long

Something amiss there... like some cowboy mechanic took the old bearings out and forgot to fit the new ones.

 

[DinghyMan]

There are several pumps shown in the parts catalogue All have 2 ball bearings
The seals should be fitted with the spring sides facing away from each other
If the shaft is not running in bearings of some sort, only supported the seals, they are not going to last long

Something amiss there... like some cowboy mechanic took the old bearings out and forgot to fit the new ones.

There are also some diagrams around showing early pumps with no bearings: e.g. Water pump kit for Volvo Penta D1A MD1B AQD2B D2A MD2 MD2A MD2B MD6A 807368 833415

Seems a bit like deliberate built in obsolescence; when the pump body wears over time then the shaft starts to run out and will then eat seals

If the bearing area is worn it could probably be machined & sleeved or a bush or bearing fitted

 

[Akestor]

There are several pumps shown in the parts catalogue All have 2 ball bearings
The seals should be fitted with the spring sides facing away from each other
If the shaft is not running in bearings of some sort, only supported the seals, they are not going to last long

Something amiss there... like some cowboy mechanic took the old bearings out and forgot to fit the new ones.

Hi Vic! In the parts catalog, the latest pump models are shown perhaps.?The pump in the engine is looking very much like this one from the old MD2B manual, seems these where problematic ancient pumps without bearings that were replaced?

 

[vyv_cox]

These pumps had plain bearings of leaded bronze or maybe copper lead. Provided they are lubricated they are perfectly good, similar to the main and big end bearings in the engine.

 

[Akestor]

There are also some diagrams around showing early pumps with no bearings: e.g. Water pump kit for Volvo Penta D1A MD1B AQD2B D2A MD2 MD2A MD2B MD6A 807368 833415

Seems a bit like deliberate built in obsolescence; when the pump body wears over time then the shaft starts to run out and will then eat seals

If the bearing area is worn it could probably be machined & sleeved or a bush or bearing fitted

That's exactly the kit for my pump. That's a nice shop, I've bought things from them, good communication also.

thanks for the info, the neck of the pump where the shaft goes through has probably be worn and is oversized. Looks like it's a more expensive repair than a new pump though!

 

[Plum]

That's exactly the kit for my pump. That's a nice shop, I've bought things from them, good communication also.

thanks for the info, the neck of the pump where the shaft goes through has probably be worn and is oversized. Looks like it's a more expensive repair than a new pump though!

Some of the plain bearing Johnson pumps have a seperate pressed in bush that can be replaced but on others the shaft runs directly in the housing. Drawing below shows the type,may not be yours. Either way, the ones I have seen have no lubrication of the shaft, other than the seawater, as the first lip seal is beyond the shaft bearing. Not good for a long life. If you can't get a replacement pump that has lubricated ball race bearings and you have to re-bush or replace with the existing type I would fit a grease nipple.

www.solocoastalsailing.co.uk

 

[Akestor]

Some of the plain bearing Johnson pumps have a seperate pressed in bush that can be replaced but on others the shaft runs directly in the housing. Drawing below shows the type,may not be yours. Either way, the ones I have seen have no lubrication of the shaft, other than the seawater, as the first lip seal is beyond the shaft bearing. Not good for a long life. If you can't get a replacement pump that has lubricated ball race bearings and you have to re-bush or replace with the existing type I would fit a grease nipple.

www.solocoastalsailing.co.uk

These pumps had plain bearings of leaded bronze or maybe copper lead. Provided they are lubricated they are perfectly good, similar to the main and big end bearings in the engine.

Mine is definitely the one without a bushing, shaft runs directly in the housing. I will uninstall the pump and go around the industrial repair zone behind the port of Piraeus and ask if they can machine it a little bit and press in a bushing from copper lead, or bronze lead
Thanks, everyone!

 

[neil_s]

My Bukh engine has a pump like that in Plum's drawing above. I have similar problems with the seals. Over the last Winter I have pressed out the worn plain bearing, replaced it with sintered bronze bushes - easily available from simplybearings - and fitted a grease nipple. All OK so far!

 

[Bilgediver]

There are several pumps shown in the parts catalogue All have 2 ball bearings
The seals should be fitted with the spring sides facing away from each other
If the shaft is not running in bearings of some sort, only supported the seals, they are not going to last long

Something amiss there... like some cowboy mechanic took the old bearings out and forgot to fit the new ones.

Unfortunately the MD2B water pumps as originally fitted had plain bearings. The seals usually fail for one of two reasons. Badly worn or grooved shafts in way of the lip seal or worn bearings allowing shaft movement. The bearing at the impeller end will wear more rapidly if the boat operates in muddy or sandy water. I have dealt with grooved shafts when putting on my tight welshman hat by replacing the normal lip seal which has the lip on the impellor end of the seal with a double lip seal which then utilises the unworn part of the shaft as well. Once the plain bearing behind the impeller wears then it needs to be rebushed or a new pump fitted. There were later pumps as Vic mentions which had a larger body and fitted with ball bearings.

 

[TernVI]

When pumps start eating seals, it's often because the shaft is worn or corroded.
It's worth checking there is no ridge or groove on the shaft where the seal runs.
Sometimes you can avoid buying a new shaft by polishing out the groove or moving the seal slightly along the shaft.
It's been known for people to fit the seal the 'wrong' way around to move the lip along the shaft a little.

 

[Akestor]

My Bukh engine has a pump like that in Plum's drawing above. I have similar problems with the seals. Over the last Winter I have pressed out the worn plain bearing, replaced it with sintered bronze bushes - easily available from simplybearings - and fitted a grease nipple. All OK so far!

Do you remember the clearance between the shaft and the new bushing? don't they overheat since they are 2 metals touching?

Here is a video i made showing the pump housing and the play of the shaft and now it's obvious why lip seals wear out so fast. The shaft is 1/2" and the pump ID around 0.5mm larger around that is too much! The housing acts as bearing and there is no extra bushing. Either this is worn out, or this is a smaller shaft but this sounds impossible..weird thing is that the narrow channel of the pump doesn't look like it's worn out. It's a nice and smooth cylindrical shape.
2 scenarios...
1) should the machine shop cast bronze inside the pump and re-drill?
2) drill a larger hole and fit in a bushing?

 

[Plum]

Do you remember the clearance between the shaft and the new bushing? don't they overheat since they are 2 metals touching?

Here is a video i made showing the pump housing and the play of the shaft and now it's obvious why lip seals wear out so fast. The shaft is 1/2" and the pump ID around 0.5mm larger around that is too much! The housing acts as bearing and there is no extra bushing. Either this is worn out, or this is a smaller shaft but this sounds impossible..weird thing is that the narrow channel of the pump doesn't look like it's worn out. It's a nice and smooth cylindrical shape.
2 scenarios...
1) should the machine shop cast bronze inside the pump and re-drill?
2) drill a larger hole and fit in a bushing?

No, it won't overheat as the bearing is water lubricated. Is you shaft worn? Is the shaft worn where the lip seals lay? If the shaft is not right it needs replacing. It can be re/ground but then you will need non-standard seals. Any decent machine shop will bush the housing for you and if you wish, add a grease nipple. It should not cost much more to get them to make an extra bush for next time.

www.solocoastalsailing.co.uk

 

[Akestor]

No, it won't overheat as the bearing is water lubricated. Is you shaft worn? Is the shaft worn where the lip seals lay? If the shaft is not right it needs replacing. It can be re/ground but then you will need non-standard seals. Any decent machine shop will bush the housing for you and if you wish, add a grease nipple. It should not cost much more to get them to make an extra bush for next time.

www.solocoastalsailing.co.uk

The shaft is in great condition no worn at all! I hope there is enough thickness in the pump walls to be machined so a bush can fit in there!

 

[scottie]

I suspect that johnson pumps which are in effect jabsco copies are metric and jabsco imperial easy to misidentify which is which over 60 years

 

[neil_s]

Yes - you have the Johnson 1/4 inch pump as fitted to early Bukh engines - mine is the F35B (3/8 inch) from later motors that has a replaceable pressed in bronze bush. I would suggest it's quite possible to bore out the worn journal and press in a bush - Your local machine shop should be able to do this. As an aside, on an earlier boat, I had a Jabsco pump with the two ball races and that was no better. It was a constant battle to keep water out of the bearings and keep them lubricated.

I have a pump just like yours on the bench in my shed - It came with the boat in an old box of odd spares - I keep thinking about preparing it as a spare for my own engine!

 

[TernVI]

I wonder if a polymer bush would be appropriate?

 

[neil_s]

Another thought - it's unlikely that your journal has worn concentrically because of the pressure exerted on one side of the bore by the swash plate in the pump chamber. Drilling out the bore will not be satisfactory because it will be off centre. Your machine shop will have to set up the pump in a lathe so that they can bore concentrically with the pump chamber. For the bush - Simplybearings do oil filled sintered bronze bushes - they don't do the exact length you need, so you would have to select a couple of appropriate sizes to make up the length needed. They don't seem to fare too well salt water lubricated but a grease nipple allows a quick shot of Ramonol a couple of times a season and this seems to have worked for my pump over the last season.

 

[Akestor]

Another thought - it's unlikely that your journal has worn concentrically because of the pressure exerted on one side of the bore by the swash plate in the pump chamber. Drilling out the bore will not be satisfactory because it will be off centre. Your machine shop will have to set up the pump in a lathe so that they can bore concentrically with the pump chamber. For the bush - Simplybearings do oil filled sintered bronze bushes - they don't do the exact length you need, so you would have to select a couple of appropriate sizes to make up the length needed. They don't seem to fare too well salt water lubricated but a grease nipple allows a quick shot of Ramonol a couple of times a season and this seems to have worked for my pump over the last season.

Great info
I went to a machine shop today and the guys sent me to another shop that does this kind of jobs specifically. The industrial zone in Piraeus has all kinds of repairs any boat or big ship needs. I let the pump to him and said he will bore it and add a phosphor bronze bushing and let a slight clearance for water lubrication. It's all he can do as there is no room to add ball bearings. Said it can last for 2-3 years. I didn't ask for a grease nipple as this could add to cost, i think i can drill this myself later! I will contact and update him to take special care on doing the enlargement concentrically.

I wonder if a polymer bush would be appropriate?

That's a good question- with added grooves for water lubrication and no clearance, tight shaft fitting.

 

[Akestor]

Yes - you have the Johnson 1/4 inch pump as fitted to early Bukh engines - mine is the F35B (3/8 inch) from later motors that has a replaceable pressed in bronze bush. I would suggest it's quite possible to bore out the worn journal and press in a bush - Your local machine shop should be able to do this. As an aside, on an earlier boat, I had a Jabsco pump with the two ball races and that was no better. It was a constant battle to keep water out of the bearings and keep them lubricated.

I have a pump just like yours on the bench in my shed - It came with the boat in an old box of odd spares - I keep thinking about preparing it as a spare for my own engine!

Maybe with a belt driven pump, we might get away with this headache! lol!