Raw Water Pump Failure
After 700 Engine hours the raw water pump on the Cummins started leaking. The leak was not immediately apparent. However the effect was quite noticeable as corrosion was visible on the port side front engine mount. Tightening the bolts on the impeller plate and hose connections did not solve the problem. A little research on the web indicated the problem might be the design of the shaft seals on the Sherwood raw water pump. Once the pump was removed it was immediately apparent that the shaft seals were the source of the problem. The Sherwood pump p/n P2701 apparently has demonstrated repeated reliability problems. The pump has been revised numerous times and has been replaced by p/n P2708 which lists for $875. A little further web searching revealed a wide range of pricing on this pump. I was able to find the pump for $577. Old pump removal and installation of the new pump was easier than expected and took less then an hour and a half. Access is excellent and nothing is too challenging. Given the wide range of pricing I would not be too surprised if the pump can be found for less.
BoatStore.com. Sherwood P2708X Pump-Cummins Qsb. SKU. 762-P2708X. Price. $577.86
I plan to get the old pump rebuilt with the newer seal design if possible for a spare. If there are any recommendations please don't hesitate to update this thread.
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Replace Sherwood Pump with SeaMax SMX-QSB model
LeTour-
I have a leaking raw water pump on my 5.9QSB 230HP (NP39001) and after reading your post I decided to do more research. In short I discovered in two blogs and on www.boatdiesel.com (excellent resource) that even the most recent Sherwood pump redesign is not reliable. Seaboard Marine in Oxnard CA rebuilds hundreds of these pumps every year and they fail constantly on fishing boats at sea.
So Seaboard Marine have come up with a replacment pump that is expensive but has been shown to be a super reliable retrofit that does not leak or catostrophically fail (shafts break or back plate is punctured etc) as the Sherwoods are famous to do. This is a Cummins issue and not related to NP Yachts. I paid $825 for a new drop in replacment pump, spare impleller, impeller puller, S&H by UPS. WWW.SBMAR.COM is the website, part number is SMX-QSB. Do your own research - but I am not going to have engine failure on a single screw boat!! We lived with a faulty 3 cylinder diesel on our sailboat and will not have that hassle again. All the best.
DaveV