Replacing the Raw Water Pump on  a Cummins engine

The Cummins 330/370 engines use a Sherwood 1730X pump for the raw water cooling. It’s a popular pump, and parts are easy to obtain, but it is not very highly regarded in the marine diesel world. The pumps have a reputation of having the shaft failing. Mine lasted 3 years and 850 hrs before the seal started to leak.

Leaks in a water pump are pretty easy to spot if you know where to look.  There are a series of slots cut in the front of the pump (the items circled in red in Figure 1). By design, when the seal leaks water will drip out of these slots.

Figure 1: Old water pump in place

If you notice water leaking from any of these slots you should replace the water pump ASAP. The back part of the pump has raw water, and the front part has oil. The seal keeps the water and oil separated. Bad things will happen if they mix.

If you voyage to Alaska , or anywhere remote for that matter, I highly recommend carrying a spare pump. I got mine from Tony Athens at Seaboard Marine (http://www.sbmar.com/)  who now manufactures a better replacement version. Figure 2 shows a replacement water pump.

Figure 2: Replacement Water Pump

In order to replace the pump, the first thing you need to do of course is to remove the old pump.  You may notice a slight problem (or to use the euphemism of my last company: a slight “opportunity for improvement”) when you go to do that. The pump is bolted to the engine by 2 15mm bolts (in the yellow circles in Figure 1).  It is impossible to remove the bottom bolt, or the pump itself for that matter, with the port engine mount in place.

You will need a small hydraulic bottle jack, or something similar, to support the corner of the engine while the mount is removed. The entire engine weighs around 1200lb, so a 1 ton 8in bottle jack has an adequate safety margin.

Figure 3: Engine supported by bottle jack, engine mount removed. New water pump has been installed.

Figure 3 shows the engine supported by a jack on the front of the oil pan. Once the jack is in place, the front port engine mount can be removed. I removed the three 15mm bolts holding the mount to the engine, and the two 19mm vertical nut/bolts holding the mount to the engine bed. Do not undo the large alignment nuts on the top of the mount. This is critical to help to ensure that you don't change the overall alignment of the engine when the mount is replaced. In addition, I marked the original location of the mount so I was sure it went back in exactly the same position (these are the blue lines in the foreground).

Once the engine mount is out of the way, you can undo the two bolts (shown circled in yellow in Figure 1) that hold the water pump in place. Now the only things holding the pump in are the large water hoses. Removing large water hoses is always a challenge.  These hoses are attached to 90 degree inlet and outlet adaptor pipes.  I ended up leaving the pipes attached to the hoses and instead unbolted the adaptor pipes from the pump in order to remove the pump.  

To install the new pump, first attach the inlet and outlet adaptor pipes to the new pump making sure that the o-rings seat properly. Once the pipes are attached, you can bolt it to the engine. 

 It took me around 3 hrs to to do this job, so be prepared for a long afternoon or a corresponding boatyard bill.

 I would like to express my thanks (again) to Jim Shates of “Annie’s Song” AT34 #47, our Sister vessel. Jim had this pump replaced under warranty, and talked me through this procedure when I did mine.

 Jeremy Bell.  AT34 #48 “Tardis”

PS What’s wrong with this photo ???

This is a picture of the old pump and impellor. It looks like I was about to lose 1 or maybe 2 vanes.