Seawater Pump R&R


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Removal and Replacement of Seawater Pump

Boat: Pacific Dragon II
Make/Model: 2002 Performance Cruising Gemini 105mc
Engine: Westerbeke 30B - 27hp Diesel
Pump Model:  33636 original
Replacement Pump: 48080 (kit number 37431)

After reading on the forums that there were some problems with the seawater pump on the 30B that could result in breakage of the drive gear, I decided to check mine.  From what I had read the seals on the shaft both are known to fail and let water into the bearing with then locks up and breaks the drive gear, which apparently requires the engine to be removed to repair.  I checked my pump with the engine running and sure enough water was dripping from the air gap between the two seals indicating failure of the water seal. 

Fortunately, after removal I discovered that the oil seal was still intact and did not allow any water to enter the bearing.  I order a replacement pump online from I also ordered the replacement seals for the old pump and was surprised by the note on the pump diagram on the site. Based on the note, Westerbeke is well aware of the problems since they issued the following service advisory on the original pump:

"This pump is covered by the following service advisory. Previously both seals on this pump (water and oil side) where specified as 33043. Because of the potential for water seal leaks, the specification has changed. Westerbeke still recommends the use of 33043 as the oil side seal, but has changed the recommendation for the water side seal. The water side seal should now be a 48013. You will also need a spacer, part number 38678 that will fit between the water and oil seal with its flat surface against the water seal."

(This note has been recently added to the site since I did not see it when I ordered the replacement seals for the pump in early April, 2006.  Fortunately, I have not bother to replace the seals in the original pump yet so I will order the new seal which is over $15 compared to the original $4 seal used previously.  Interestingly, I could not find the same service advisory on the Westerbeke website. Also, I did not include the link directly to the diagram since strangely the note does not appear by linking directly to the page, probably due to the long URL used by their site navigation.) 

Here is a picture of the old pump after I removed it.  If you pump has the problem you will see water dripping from the air gap which is supposed to prevent water from reaching the bearing in case of failure which it did in my case.  Note: There is a rubber o-rig on the shaft that acts as a throw-off when the shaft is spinning for water to help prevent the water reaching the oil seal on the opposite side of the air gap.
(Click on Picture to see larger image.)

Here is a picture of the impeller after opening the cover.  Notice the shape of the impeller compartment on the old pump is not round.  This makes it much easier to get to the hard to reach inside nuts that secure the pump to the engine.

(Click on Picture to see larger image.)


 Here a picture of the new pump with the cover open.  Notice the round shape of the pump and the nice o-ring replacing the paper gasket.  The downside to the new pump is the difficulty of getting to the inside mounting nuts.
(Click on Picture to see larger image.)

Here is the cover of the new pump where you can clearly see the pump part number which is 48080; however the replacement kit is 37431 which includes both pipe fittings (the 90 degree elbow included in the kit happens to be too small to fit the existing hoses.) 

(Click on Picture to see larger image.)

What should have been a straight forward job to replace the pump turned into a real challenge.  First of all the replacement pump comes with a much smaller elbow than what is needed for the existing hoses.  So I was forced to remove the old elbow for the old pump to get the new one operational which required two trips to the hardware store to find tools to get the bugger off.  If you know that you will be taken the elbow off the old pump, I recommend that you have a vice handy to hold it while you turn it with a big pipe wrench. 

Here is a picture of the side of the engine with the pump off.  You can see how little space there is to get to the studs on the inside of the pump; needed special tools to tighten the nuts and lots of patients. I found an small inexpensive ACE 1/4 inch drive socket set that did the trick.
(Click on Picture to see larger image.)

To top it off, one of the four studs insisted on coming out instead of the nut coming off of it (notice in the bottom of the picture above.)  The paint they apply on the engine was acting like thread lock and despite my best efforts I was forced to use it like a bolt which turned out to be actually easier than trying to get the washers and nuts on the stud.

Anyway to make a long story short, be patient with the installation and be prepared to make several trips down to the hardware store as you encounter new obstacles that require special tools. 

Once you get the new pump in place you will need to prime it.  Fortunately the fresh water flush connection on the thru hull provides an easy way to do this.  Since I was working alone I used two garden hoses with a plastic shutoff valve in the middle next to me at the engine so I could control the water flow without having to move.  With the top hose off of the water pump I ran the water just until it started to come out of the top of the pump.  Now attach the top hose to the pump, turn on the water and start the engine.  Water will start flowing almost immediately out the stern.  After letting it flush all the air out of the system for a few minutes you can switch the thru hull to the seawater position a verify that water continues to flow out the back. Note: I am planning to add a connection from the on board pressure water system to allow the system to be easily primed while out at sea after an impeller change.  

I later ordered another 1" elbow part number 36612 to put in the old pump so I have a complete spare replacement pump.

In conclusion, I recommend that all Westerbeke 30B owners check their pump for leaks.  If it is leaking you should either replace the pump or repair it by installing new seals and you may as well change the bearings while your at it.  The experience will certainly prepare you in the event that you have to replace or rebuild the pump at sea. Although expensive, buying the replacement and installing it will minimize the down time on the engine and leaves you with a spare after repairing the old pump.  Just be sure that you have the right size elbow for the water hose connection if you do purchase the new pump kit.


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This site was last updated 09/01/03