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angus99

Guru
Joined
Feb 19, 2012
Messages
2,764
Location
US
Vessel Name
Stella Maris
Vessel Make
Defever 44
We have an older Westerbeke 12.5 WMD generator aboard Stella Maris. It’s developed a leak in the raw water pump which seems to be coming from somewhere near the forward-most part of the shaft—not the impeller cover. It’s still pumping plenty of water and I can rig a funnel and bucket which will handle the leak for hours—perhaps days—so it’s not overly large. Can someone with modest mechanical skills rebuild a pump like this or is it better to send it to a shop or replace it?
 
Is it belt driven or direct drive?

Rebuilding a raw water pump isn’t difficult. However, the correct parts are required and the ability to determine whether the shaft is damaged or worn as to whether a new front water seal will solve the problem. Depending on the design, you may also get salt water in the bearings, necessitating their replacement (should be done anyway). My point is that a leak is one issue that you may be able to live with short term. All bets are off if there's salt water getting in the bearings.

I always have replacement pumps available ready to go. For some pumps, a rebuild kit is reasonable price wise. For others, it can be half the price of the pump. It you have a damaged or worn shaft, buy a new pump.

Ted
 
It’s leaking at the shaft seal. They have kits to rebuild the pump. Not that hard, but it’s a gamble if you don’t buy the new shaft, which when added up, comes close to just buying a new pump. The old shaft can develop wear at the contact area of the seal. You generally can’t see the wear. You find out after you rebuild the pump and reinstall and after running for awhile, it develops a minute drip-very frustrating. I suppose it will depend on how easy it is to remove the pump and the cost difference. Im wondering if anyone has had success buffing the shaft at the wear point without getting it out of tolerance.
 
It’s leaking at the shaft seal. They have kits to rebuild the pump. Not that hard, but it’s a gamble if you don’t buy the new shaft, which when added up, comes close to just buying a new pump. The old shaft can develop wear at the contact area of the seal. You generally can’t see the wear. You find out after you rebuild the pump and reinstall and after running for awhile, it develops a minute drip-very frustrating. I suppose it will depend on how easy it is to remove the pump and the cost difference. Im wondering if anyone has had success buffing the shaft at the wear point without getting it out of tolerance.
There are several ways the seal is done to the shaft. IMO, the nicest involves a disc that seals to the shaft with orings. The actual seal is ceramic going against the disc. Wish I could remember which engine that pump seal was on.

Ted
 
I have the same 12.5 BTDB. I've never bothered doing my own rebuild. Last Year a new pump from DEPCO was less than $400 and $73 plus shipping to have them rebuild old pump including new impeller. If the pump is worn to the point of rebuild being unreasonable they will call you. It's what they do and they do it well and at a reasonable price. I use them to source and rebuild all my pumps. My contact is Kevin Holland in Service Dept. (727) 446-1656.
 
There are several ways the seal is done to the shaft. IMO, the nicest involves a disc that seals to the shaft with orings. The actual seal is ceramic going against the disc. Wish I could remember which engine that pump seal was on.

Ted
The shaft spins, so it has to touch something. It will (over time) wear at the point of contact. The new seal will not be able to work on the damaged shaft. That’s why dripless shaft seals has you move the seal on the shaft (PSS).
 
The shaft spins, so it has to touch something. It will (over time) wear at the point of contact. The new seal will not be able to work on the damaged shaft. That’s why dripless shaft seals has you move the seal on the shaft (PSS).
As on the PSS shaft seal, the disc is sealed to the shaft with orings. The disc and the shaft turn as one, so no wear. With the pump seal I mentioned, both the ceramic seal and the disc are part of the replacement seal kit. Believe it's the raw water pump on the 4045 John Deere.

Ted
 
As on the PSS shaft seal, the disc is sealed to the shaft with orings. The disc and the shaft turn as one, so no wear. With the pump seal I mentioned, both the ceramic seal and the disc are part of the replacement seal kit. Believe it's the raw water pump on the 4045 John Deere.

Ted
I see. Great design. I might be thinking of my tides marine with the lip seal instead of the PSS shaft seal (previous boat). Thanks for the clarification.
 
Thanks, guys. I thought of Depco after I posted. That seems the safest way to go.
 
On our 12.5 replacing the pump was the cure, with a spare then kept onboard. As best I could see a failed inner seal could put some water in the oil so a rebuild was not contemplated.
 
If the pump is in good condition and the shaft is good, a rebuild is an economical way to have a reliable back up. That’s why I don’t rebuild ‘em myself. I could do the rebuild, but don’t have the knowledge base/experience to know when that’s not the right choice.

As an aside , my JD 6068’s Johnson pumps have a known design flaw leading to (fortunately) an oil seal leak sometimes as early as 50 hrs on a new pump. Depco has been a marvelous asset for me - rebuilding/replacing my Johnson pumps when the oil leak starts, they have pioneered a few fixes to extend the life of the oil seals to 400-800 hrs so far. Hopefully the latest iteration of those pumps (I believe Gen IV or V) will permanently eliminate the issue.
 
I'll second the Depco recommendation. I had a similar problem, just couldn't keep shaft seals from leaking, was getting less than 400 hrs. I finally removed the pump, bolted on a cover plate, installed an electric pump near the heat exchanger. The pump was powered by the output of the genset, and was controlled by a NC relay that paralleled the preheat hold in relay in order to prevent the motor from starting until the preheat switch was released, thereby allowing the genset to build speed and output voltage. No more impellers, shaft seal leaks, and my pump maintenance just disappeared. It just worked. An occasional relay failure, but that would have happened despite the pump being installed. Ate a capacitor until I determined that the pump was starting while the voltage was ramping up. The delay provided by the preheat switch was an elegant solution and never lost another cap. Used an all stainless pump from Depco, they helped with recommending a pump that closely matched the pump curve on the OEM seawater pump. I never regretted ditching the engine driven pump.
 
Well, my pump is on the way to Depco. I will post whether it can be salvaged or if I need to pursue a fix like Steve’s.

Thanks, all.
 
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