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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