Raw Water Pump Shaft

[Oil Gypsy]

I am servicing my raw water pump, was going to replace all bearings and seals. After stripping the pump down I've found two small score marks on the shaft where the impeller side lip seal sits. They dont seem to be major indents but when I press heavily and scrape my finger nail over them you can feel the ridges. There aren't any major burrs on the edge of the scores.

Never having seen this before I'm wondering how much wear is acceptable and if the shaft is still usable, to get a new shaft is going to take two to three weeks (50 year old pump) and the cost of a new pump is prohibitive.

 

[diver dave]

I would use 220, 400, then 600 wet on it.

 

[jleonard]

I'd assemble as is and see if it leaks. I had one similar and it never leaked with a new seal.
A little very light wet sanding wouldn't hurt.

 

[C lectric]

Agree about the sanding but go even finer as close to the current finish as possible. Consider a Dremel tool with the polishing wheels and some 1,000 grit polish. Maybe some valve lapping compound if available fine enough.

Also consider using a Speedi Sleeve, SS. Bought for the shaft size it is a thin sleeve that is tapped over the damaged area on the shaft. It does need to be Loctited into place but does not need gobs of Loctite.

Available from bearing supply shops. Tell them what the application is and ask about a seal that is just a hair larger ID to accomodate the sleeve.
Take the shaft with you.

I did finally replace the RWP shaft but not because of some minor lip seal wear on the shaft, rather the drive splines were worn enough that the hub of the impellor was trying to ride over the splines.

 

[Lepke]

Crocus cloth, maybe. It's about 1000 grit. The shaft needs to be smooth otherwise it will eat the new seal. Sand paper is too coarse.

The are 2 ways to fix the shaft. There are sleeves that slide over the shaft and give a new surface for the seal to rub against. Or hard chrome the area and polish it down to near the original size. Probably more expensive than a new shaft, but used a lot in commercial fishing on hydraulic motors where the ss shaft gets crevice corrosion when exposed to salt water.
The sleeves should be available on line or a a bearing supply. Search for "shaft repair sleeve" on ebay. Maybe shaft repair collar.

 

[kchace]

Even McMaster has them.

 

[Bmarler]

if you can spin it up in a lathe you can polish it and retain it's concentricity even if it's a bit undersize. if it were mine, i'd polish it and re-assemble. order a replacement shaft, bearings and seal and put those in my spares. that thing could last years, or if unlucky, much less.
not sure how that pump is arranged, but if there's a danger of getting raw water into the engine oil i might think about waiting for the new shaft to arrive and skip the sleeve idea.

 

[ancora]

Shaft savers is the way to go...they are a lot cheaper than replacing the shaft.

 

[Nick F]

Remember that the lip seal that seals against this part of the shaft is a "static" seal - there is no rotation between the lip seal and the shaft. You will probably still have a leak-free seal with the shaft as is.

I agree that some dressing (mild rubbing) with very fine abrasive (crocus cloth) is a good idea.

 

[Bmarler]

Remember that the lip seal that seals against this part of the shaft is a "static" seal - there is no rotation between the lip seal and the shaft. You will probably still have a leak-free seal with the shaft as is.

I agree that some dressing (mild rubbing) with very fine abrasive (crocus cloth) is a good idea.

Is this a mechanical seal instead of a simple lip seal? If that’s the case I probably wouldn’t worry about it.

 

[diver dave]

One of many shaft definitions: : a commonly cylindrical bar used to support rotating pieces or to transmit power

So, a shaft seal is typically called a dynamic seal. Seal is fixed, shaft rotates. After a long while, the seal lip removes some shaft material.

Is an important fact missing? [emoji848]

 

[Nick F]

Is this a mechanical seal instead of a simple lip seal? If that’s the case I probably wouldn’t worry about it.

You can tell by looking at the seal that came out. All the raw water pumps that I have seen have had mechanical seals*. I would be extremely surprised to see a seal that rubs on the shaft.

* in a mechanical seal the sliding (dynamic) seal is done by a pair of highly polished ceramic faces pushed together by a spring. One of these 2 faces is statically sealed to the shaft by an elastomeric ("rubber") seal.

Nick

 

[Bmarler]

You can tell by looking at the seal that came out. All the raw water pumps that I have seen have had mechanical seals*. I would be extremely surprised to see a seal that rubs on the shaft.

* in a mechanical seal the sliding (dynamic) seal is done by a pair of highly polished ceramic faces pushed together by a spring. One of these 2 faces is statically sealed to the shaft by an elastomeric ("rubber") seal.

Nick

i have had raw water pumps with common lip seals. when i looked at the OP's picture and saw the wear on the shaft it made me think it was a simple lip seal. with a mechanical seal it's unlikely to get wear like that unless the portion that rides on the shaft was slipping.
with a pump who's shaft is driven by the engine, there's also the possibility of a simple lip seal for the oil side. is that what we're seeing?
do we know how this pump is configured? that would weigh in my decision of whether or not to run this shaft as-is or repair/replace.

 

[Oil Gypsy]

Hello,

Ive reassembled the pump with new bearings and seals which came as a kit (the seals are standard lip seals), I polished the shaft up to 2000 grit wet & dry, no burrs but you could feel the groove with your finger nail. I have ordered a new shaft but its coming from the States and will take several weeks to arrive.

The pump is a Jabsco 5850 on a Lehman 120, if original its 50 years old. When I stripped it down it had a lip seal on the oil side and an old style brass seal on the water side, where the oil seal sits there was no wear. When I stripped it down there was a rubber seal missing which should have been located behind the water side seal.

The boat has twin engines, given what I found I removed the second pump and stripped it down, although the pump wasn't leaking the shaft is in similar or slightly worse condition with more grooves where the water side seal sits, these grooves are slightly deeper than the first pump (which was leaking). Given the cost of a new shaft Ive decided to try the Speedi-Seal route, unfortunately this is proving to be quite difficult as there are none available locally, if I buy online the cost of shipping is as much or more than the seal itself, strangely shipping from Europe appears to be cheaper than from either Canada or the US. Ive only been looking for a day if anyone knows of a local supplier Please let me know.

 

[C lectric]

Maybe you have tried them already but
Wolff Marine
will likely be able to help if anyone nearby can.

Give them a phone call. John is the pump guy. They are in Richmond.

 

[diver dave]

Or, Depco in Clearwater

 

[Oil Gypsy]

To finish this story off..

I purchased SKF Speedi sleeves from Rock Auto, they had the most competitive price and fastest (and cheapest) shipping. I installed the seal without problem, the top edge of the sleeve was about 2-3 mm from the impeller shaft grooves, the installation was an amazingly simple process.

I also had a spare pump on the boat that has been sitting in to bowels of the V-Berth since we became owners. After I had finished the first pump I stripped the spare one as well, the shaft was in much worse condition deeply scored and pitted where the seal sits, (unfortunatly I lost the pictures of it). With this one I ground out the worst and filled the groove with JB Marine Weld, smoothing it down after it had cured and polishing the shaft with 1500 W&D. I used my second Speedi Sleeve to cover the repaired section of the shaft. It seems no different from the first shaft I repaired.

This pump will be kept as a spare (a get me home pump - if needed). Just waiting for new bearings and seals to arrive.