The Configuration
 

     The Raw Water Pump on Mikhaya is configured differently than possibly you will find on your boat.  The credit to this design goes to the previous owner.  Basically the impeller and pulley belt housing has been turned around so the belt is in the rear and the impeller access is to the front.  The reason for the change was to provide access for inspection and changing of the impeller, as you will see.  Thumb screws are used to secure the impeller plate cover on.  The top picture shows a white line drawn to the original configuration of the raw water pump on the Westerbeke engine.  You can see the belt is in the front.  The bottom two pictures show the modification on Mikhaya.

Checking the Impeller

    

Start off by turning the Raw Water intake thru hull to the OFF position.  Pictures 1 & 2 show the thru hull valve and the outside intake on Mikhaya.      In picture 3, you see the pump assembly disassembled.  I DID NOT HAVE TO REMOVE THIS ASSEMBLY ON Mikhaya.  I was changing the belt at the same time so that's why you see it disconnected.  If you have the original configuration you might have to disassemble the pump to get at the impeller, which has a rear access point.      Remove the cover on the pump by removing the six(6) thumb screws show in picture 4.  Note the way the rubber wheels are turned to rotate CW.      Remove the impeller wheel by using a pair of nettle-nose-pliers.  Work the wheel back and forth slowly.  It is held in with the pressure of the center staff and the cover only.  In picture 5 you can see the impeller wheel removed and the interior of the pump. (Picture taken before engine rebuild.)  When you inspect the rubber wheel you want to look for any missing "fins," cuts and general rubber ware.  Replace this wheel if you see any damaged rubber at all. (My impeller kit was Jabsco 18673-0001 that fits on a Jabsco Pump model 2620-0001.)  Don't forget to replace your spare kit, assuming that you had one to begin with.      (Picture 6) After placing the wheel back on the shaft, clean the cover plate and replace the rubber gasket supplied with the impeller kit.  Give the cover a light coat of white marine grease.  Line up the cover with pump housing and replace the thumb-screws.  Make sure you have a good tight seal.      Turn the Raw Water thru hull valve back on.  Ready the engine for running and fire it up.  Check the seal for leaks and that you have a good pulsing flow of water out the stern of the boat.

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Some Thoughts
    * Be sure to check for bits of rubber in the pump out hose.

      * You can establish a reference for the water flow by holding a gallon bucker over the stern exhaust while the engine is is running at some fixed RPM.  This will provide a GPH reference.

        (Previous owner measured this before my engine rebuild at:

        1000 RPM - 1 gal - 21 sec

        1500 RPM - 1 gal - 16 sec

     * If your engine is getting too hot at idle and your raw water pump is working properly, you might have barnacles growing on the intake screen.  Dive and scrape.

     * I check my impeller about every 6 months.

     * Don't let the raw water pump run dry.  It will heat up and destroy the rubber impeller.