I’ll need to see what I have, but I believe the pump on my Westerbeke 40 is the 
brass plate version you described.  A significant problem with my pump is 
inadequate suction.  We have looked repeatedly to see if impeller pieces were 
sucked into the system (found a couple).  The suction is so weak that I need to 
do the funnel-from-on-high routine to get the system working after spring 
launch.  I also sometimes need to do the funnel routine after being heeled over 
and bouncing around in bad weather.  I would welcome a more powerful pump. 

From: Dennis C. via CnC-List 
Sent: Thursday, March 29, 2018 1:01 PM
To: CnClist 
Cc: Dennis C. 
Subject: Stus-List Universal / Westerbeke Sherwood raw water pump upgrade

For those of us who have Universal or Westerbeke diesels that use the Sherwood 
G908 clamp mount raw water pump, here's some news.  (The Westerbeke number is 
sometimes 42175.) 

Changing the impeller on the Sherwood is a bit of a pain because the bolts come 
in from behind.  You can either remove the pump by removing the two clamps, or 
remove the pump case by removing the 3 bolts and lifting the case off.  Then 
you have to make sure the o-ring is properly seated upon reassembly.

Another issue with the Sherwood is that it often leaks.  Unlike many pumps that 
have a shaft seal, the Sherwood impeller seals against a brass wear plate on 
the back of the pump.  If the wear plate, which is fairly thin, bows outward or 
has excessive wear, the pump will leak raw water.  In a salt water environment, 
this tends to have a deleterious effect on the engine front.

I replaced the thin wear plate on my Sherwood with a thicker stainless wear 
plate that I found on eBay.  That helped reduce a nagging leak.


Although I don't need it yet, I found a drop in replacement, Oberdorfer 
N202M-908.  This pump is a more traditional design with shaft seals.  Access to 
the impeller is from the front by removing the cover plate.

The Oberdorfer N202M pump has been around for many years and is a standard 
marine engine raw water pump.  A version is used on the good old Atomic 4. It 
fits many marine diesels by being available in several models.  The differences 
are in the mounts for attaching it to the engine.  Some resourceful boat owners 
have modified Oberdorfer N202M-16's to fit the clamp mount configuration.  
Oberdorfer now offers the clamp mount as the 908 model.


I found one thread on a Catalina owners site which questioned the pumping 
capacity of the Oberdorfer on an M-35 engine.  I was not able to find the 
capacities of the two pumps but found many posts from boatowners who were using 
the Oberdorfer N202 series pumps on various Westerbekes and Universals 
successfully.

The other good news is the Oberdorfer is a fraction of the cost of the Sherwood.

I'm considering replacing the Sherwood with the Oberdorfer even though the 
Sherwood is doing fine....right now.

Dennis C.
Touche' 35-1 #83
Mandeville, LA


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