Changing the Raw Water Pump


Dirona is powered by twin Cummins Diamond 270B.  These are turbo charged, jacket water aftercooled Cummins B-Series engines rated at 270 HP.  They each depend upon a Cummins part number 3866493 raw water pump which is a Sherwood P1730X.  These pumps are about $750 from Cummins which is simply nuts or about $580 from a Sherwood dealer.  I've purchased one as low as $450 in the heat of the dot com craze but that price is no longer available (apparently companies actually have to make money to stay in business).  Tony Athens at Seaboard Marine sells them for $525 with the gasket.

I had a new raw water pump installed on my starboard engine under warrantee at about 150 hours due to leaking oil. At about 1150 hours (2.5 years), the port side started leaking oil. At 1200 hours the starboard side again started leaking oil and, this time a fair amount of raw water as well.   I've been ignoring the oil drip on the port side since the leak is very minor but the raw water leak is nasty in that it sprays salt water mixed with oil around the bilges so I changed it today.  And, I've been warned that pumps leaking raw water are prone to some nasty failure modes including bearing failure which, on failure, can damage the engine timing gears as well. 

My pumps are close to impossible to remove without first removing the engine mount so I put a hydraulic jack under the engine and lifted it slightly, removed the engine mount, and then removed and replaced the pump. Previously, I had wasted over an hour failing to get it off whereas this afternoon, with the engine mount off, it was pretty easy to change. The whole operation took 2 hours and 15 min to get it back running. I then spent another 45 min cleaning up, painting the pump, and cleaning up the bilges from the raw water leak. First removing the engine mount seemed to work well.

The pump prior to removal.  I had wrapped an oil diaper around it to keep the salt water spray under control.












Note how removing the engine mount allows much better access to the pump.  I used a hydraulic jack under the front of the engine oil sump to support the engine while the mount was off.  Be careful to get the mount in exactly the same location and adjustment or you'll need to re-align the prop shaft as part of this job.

Here's the old pump.  Since both the oil seal and the raw water seal are leaking, the pump was throwing off a slurry of raw water mixed with oil when running so it needed to be changed.  The raw water is likely beginning to make a mess of the pump bearings.












Here's the new pump installed.  I've circled the lower pump mounting bolt in the left photo.  That's the difficult one to access without first removing the engine mount.












The pumps back on the engine, cleaned up and painted.












As it turns out, the pump impeller is also in the process of failing with one broken impeller blade and a couple of others with cracks.  This impeller has only 1 year and 350 hours on it which is surprisingly low to be showing this sort of wear.  I normally change every year so it was due but, after a year, they normally aren't in bad shape.

I checked the port-side impeller since it was last changed at the same time and it's in excellent condition so it would appear that this impeller failure was either a statistical anomaly or contributed to by the other problems with which this pump has been operating.



Cummins builds excellent engines and these two continue to serve me well but, generally, the water pump is a weak link.  In my opinion the Sherwood P1730X simply don't have the service life needed in this type of application although they do pump a large volume of water so I do have plenty of reserve cooling in this 270HP application.

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Copyright 2012 Jennifer and James Hamilton