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Sail 4900
Last seen: 4 months 1 week ago
Joined: 12/6/16
Posts: 6
Sherwood Raw Water Seal Question

Quick questions about the water seal on the Sherwood G908 raw water pump.  About a year ago I replaced the raw water impeller but noticed slight leakage at the pump housing weap hole recenlty.  After pulling it apart I noticed these small holes/indents in the attached photo at the rasied circular sealing surface which I had mounted against the steel plate surface and towards the engine.  Didn't know the impeller was directional and perhaps it's not but it seems these holes offer a pretty clear path for water to get past and into the area between the impeller and bearing housing.  So the questions are: 1.  Is the raised circular rubber part of the impeller the primary water seal or is it the spring tensioned rubber washer and ceramic glide bearing that are behind the impeller and over the shaft?   2.  Is the impeller directional in relation to the small indents in the attached photo?

Thanks,
Mike Shea 
Vento Caldo 2098

Haro's picture
Haro
Last seen: 4 days 6 hours ago
Joined: 11/7/14
Posts: 269

I do not believe the impeller is directional, it certainly is not the cause of water at the weep holes. Many owners are disappointed at the poor performance of Sherwood and have switched to Orberdorfer. At this point I would recommend removing the pump from the engine and cleaning the shaft and the seal rubber surfaces inside with paper towel and water. After drying apply lana-coat to shaf surface and the rubber surfaces of seals and reassemble the pump and reinstall
You will find no water at the weepholes.
If it continues to leak consider Orberdorfer.
See my link on my signature for content on this with photos.

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Ray Taylor
Last seen: 3 hours 39 sec ago
Joined: 9/11/19
Posts: 19

I know this goes against popular opinion but I’ve personally had pretty good luck with the Sherwood G908 and feel that it’s a good design.   The weakness is that the internal water seal will begin to leak in time.   Westerbeke recommends overhaul at 1000 hours. IMHO stay within this and you’ll be ok.    

I’ve overhauled about 6 of these pumps for myself and others but am far from an expert.   As stated the impeller will go in either way.  The raised lip on the impeller seals the impeller to the pump face and brass wear plate for efficient pumping.   

The water drip you see is water passing through the internal seal, which is either worn or damaged.    The drain holes in the pump body are designed to prevent water from entering the bearings.   The pump body drains prevents pump pressure forcing raw water into the bearings.   In time the bearings will fail.  

Again in my opinion, leakage from this area should be addressed quickly to prevent bearing damage.    

The photo attached are a water side seal prior to being pressed on the shaft.  The other photo is a pump and parts during a rebuild.   Note this pump had 1068 hours at the time of rebuild with no leaks or other problems. 

 

Attachments
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Ray & Janice Taylor
"Mizu"
Hood River, Ore.
#2113 2002 TM
 
Sail 4900
Last seen: 4 months 1 week ago
Joined: 12/6/16
Posts: 6

Thanks for the info.  Did you heat the bearing housing to get them out and in?

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Ray Taylor
Last seen: 3 hours 39 sec ago
Joined: 9/11/19
Posts: 19

No heat is required. The water side seal is 2 parts held together by a spring.  One side is pressed into the bearing housing and the other bonds to the pump shaft.   They squish together forming a seal between the bearing housing and the pump.   
If you change the seal you should also change out the bearings.   I suspect they have already been damaged and they are not expensive.     The entire rebuild kit from Westerbeke is $150 ish.   New oil seal, new water seal asembly, new wear plate, impeller, screws, and gaskets.    If you choose to overhaul your pump, let me know and I'll walk you through the process.   I agree that the Oberdorfer is a fine pump, simpler in design and a cost effective solution.

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Ray & Janice Taylor
"Mizu"
Hood River, Ore.
#2113 2002 TM
 
Sail 4900
Last seen: 4 months 1 week ago
Joined: 12/6/16
Posts: 6

How did you get the bearings out of the casting?  I susect heat will help but I don't want to pound them out.

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Ray Taylor
Last seen: 3 hours 39 sec ago
Joined: 9/11/19
Posts: 19

The short answer is that I don’t heat the bearing housing.   Just remove the circle clips and press the bearings out.   The bearings will come out with the pump shaft.  You can heat the bearing housing if you want but it’s not necessary.   It’s important not to put pressure on the pump shaft.  Use some sort of bushing (most use sockets) that pushes on the shoulder of the bearings (not the end of the pump shaft).   Since the bearings will be replaced no need to be gentle.   

I use a hydraulic press to remove and insert the bearings.  It takes a fair amount of force to move the bearings but they push right out.      You could probably do the work with a large vise and probably even a hammer.    

The photo shows the bearing removed from the housing attached to the pump shaft.   Leading to the next challenge.  There is a circle clip between the bearings.   This clip needs to upset or removed before the shaft can be pressed out.  

Attachments
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Ray & Janice Taylor
"Mizu"
Hood River, Ore.
#2113 2002 TM
 
two-rocks
Last seen: 4 hours 58 min ago
Joined: 8/11/17
Posts: 67

The sherwood is a bad design. Way too many parts. Way overpriced. Replacing the impeller is a pain and there is no need for such nonsence. Go Oberdorfer.

 

LeslieTroyer's picture
LeslieTroyer
Last seen: 8 hours 4 min ago
Joined: 3/13/16
Posts: 507

Leaking from the weep hole is an indication that the water seals are worn out and you need to replace the bearings and seals (nothing to do with the impeller).  

 

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Les & Trish Troyer
Mahalo 
Everett, WA
1983 C-36 Hull #0094
C-36 MK 1 Technical Editor. 

Commodore

 

vainise
Last seen: 3 months 3 weeks ago
Joined: 4/4/10
Posts: 1

I own a catalina 36MKII with Sherwood water pump. The problem was that during winter the sealing device dried up and ceramic ring stick withe grafite ring. Consequence substantial leakage with bearings corrosino and engine washed by salt water.
I made a bronze ring which fits the inside of the pump and with a cavity to fit 2 regular sealing on the inner part. I selected sealings in Viton with inner spring in SS. I glued the bronze housing of  the sealings to the pump shell , using a 2 part epoxy glue. The modified pump lasted 10 yaers , before replacing the viton seals.  Problem solved. 
I apologise for my english .
Boat lying in Sardinia Italy

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