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Old 08-24-2019, 11:55 PM   #1
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Oxidation on Raw Water Pump

About 6 years ago, I had the raw water pumps on my Perkins 6.635 engines replaced. I now have about 300 total hours on the engines.

During my recent cruise, I noted there is now prominent oxidation (copper petina) on the exterior of the raw water pumps, but they are working well. Movement of raw water through the cooling system has been fine and they are not leaking. The seal cap is intact.

Should I do anything with this oxidation? Should I strip this petina off? What would work for this?


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Old 08-25-2019, 01:47 AM   #2
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I would look at whether the pumps needs new seals. Are the pumps new or rebuilt? It looks like the heaviest concentration of corrosion both on the pump body and the nearby steel is near the weep holes; inside you can see the slinger oring that will throw any leaking raw water, and explain the corrosion. In fact it even looks damp in there to me... Is it possible they are just starting to seep some raw water and haven't yet started to noticeably leak? It might be time for a new minor kit (ie new water seal) for that pump...

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Not sure if this is your exact pump or not, but found the below drawing as one style used on the Perkins - the clamp style Jabsco that looks at least very close. It appears there is a combined three piece water seal in there between the impeller and the slinger.

Here is the site I found that drawing from, it is for a Jabsco 9990-21, which is the current edition of the 9990-41 evidently. I've never had one of the clamp mount style, but these pumps are all very similar in nature.

https://www.pumpvendor.com/Jabsco_9990-21_parts.html

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Old 08-25-2019, 05:46 AM   #3
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I agree with the PP that the corrosion is probably being caused by the seal leaking. I see evaporated sea water residue in the pic as well as the patina. Fix the seal but don't worry about the patina. The pump body is bronze and bronze statues develop a heavy patina that adds to their appeal and they last for centuries.



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Old 08-25-2019, 05:50 AM   #4
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Yes, it appears as though the raw water pump seal is leaking. Depending on the pump model, you may need to disassemble the pump to replace the seal.

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Old 08-25-2019, 08:40 PM   #5
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Quote:
Originally Posted by fractalphreak View Post
Are the pumps new or rebuilt?
According to my paperwork, the pumps were Jabsco 99990-41 installed by Suldans Boat Works, Port Orchard, WA. They were purchased from Fishermans Supply. I can't tell if the vendor to Fishermans's shipped rebuilts or new pumps.

I already have impeller replacement kits on board, but will order the Minor seal kits as well.

https://www.pumpvendor.com/Jabsco_9990-21MNK.html

Looks like I just need to unbolt the pump from the mount and replace the seals, replace the impellers, and clean up the mess. Let me know if there are any "tricks of the trade" to be aware of....

Thanks..
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Old 08-25-2019, 10:28 PM   #6
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Just replaced my raw water pump on the genset and rebuilt the old one to keep as a spare. I was completely ignorant on the way in. I replaced seals and bearings (I wanted to replace the corroded shaft also but they wanted $110 for a 2 inch by 1/4" diameter piece of stainless!!! - cleaned it up and buffed it to shiny instead).

There are lots of Youtube videos of raw water pump rebuilds - you may not find one with your exact model pump, but the process is virtually the same for all. Lots of tips for pressing out the bearings, etc. Also find the exploded diagram for it online.

I just watched ALL of them and then went on in. I guess I won't know if I was successful until I need the spare!!
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Old 08-26-2019, 09:05 PM   #7
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Hopefully someone who has rebuilt these exact pumps can provide some exact insight or quirks.

My past experiences with raw water pumps is make sure the bearings and their seals are not compromised - sometimes the leaking (or just starting to weep) water seal is the symptom of the shaft wobbling from other issues - like worn bearings.

Hopefully you are catching it in time and no seawater has made it to the bearings. It looks like your particular pump design does a decent job of separating the bearings from raw water - it has the slinger o-ring plus another seal protecting the bearings.

My last boat had OMC gas V-8's with Sherwood G46 pumps in them, and each time I noted a seal was shot it cost me the bearings too (read- major kit) because they weren't independently sealed in that pump. My first sign of the seal wearing was weeping seawater from the weep hole, and by then it was too late for the bearings!

This is reminding me that there are some spare parts that I would be more comfortable having on hand and a minor and major kit are two of them...
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