• Crusader Marine Engine Replacing A Raw Water Impeller - Sherwood Pump


    In most cases it is much easier to remove the pump from the engine. the engine below is connected to a V-drive so it sits in the boat backwards with the front of the engine facing the stern. The pump is located below the oil cooler.

    Attachment 511

    This is a view from the front of the engine.

    Attachment 512

    Removal requires two hose clamps to be disconnected and two bolts located on the bottom of the pump mounting bracket to be removed. You cannot see these two bolts without the aid of a mirror.

    View of pump from the front.

    Attachment 515

    Remove the four bolts in the impeller cover plate as shown in the picture below. Once the bolts are removed tap lightly on the cover plate to loosen the seal on the old gasket. Slide a regular screwdriver under the cover and carefully slide the cover plate off.
    Attachment 514

    With the coverplate removed the impeller is exposed. Note the condition of the vanes on the impeller, if any are missing they must be recovered to prevent blockage of the oil cooler and other engine water passages. They are typically in the pump discharge hose or the oil cooler inlet.
    Attachment 516

    Prior to removing the impeller note the direction the vanes are curled. In the picture above the vanes are curled to the right, that means the pump rotates counter clockwise from this view. When you insert the new impeller you will have to curl the vanes in the same direction as the original impeller.

    With the old impeller removed clean out any debris found in the impeller chamber. Remove all residue and old gasket material from the pump housing and the cover plate. You should notice the impeller shaft is "keyed" and you will find a half moon shaped key. Using a marker place a mark on the backside of the pump pulley aligned with the key. This will help in aligning the new impeller during installation.

    To install the new impeller lubricate the impeller chamber with mild dish washing detergent. This will help the impeller slide in the chamber easier. Slide the new impeller onto the shaft aligning the key slot in the impeller with the mark you made on the pulley. The impeller should slide up to but not enter the chamber. The impeller is designed to be slightly larger than the chamber and the chamber also has a slightly flattened area. When the impeller rests on the housing you will have to curl the vanes in the direction you noted above. This may take some time but concentrate on curling the impeller vanes at the flattened area pushing in on the impeller at the same time. The impeller should eventually slide into the chamber approximately 1/4 of an inch.

    The impeller is now resting against the key on the shaft. Check your mark on the pulley and the slot in the impeller and ensure they are aligned. Continue to apply pressure pushing the impeller into the chamber while slightly rotating the pulley back and forth. You should feel the impeller slip onto the key. You will know this by moving the pulley slightly and noting the impeller moves as the shaft is moved.

    Once the impeller is on the key, rotate the pulley in the direction of pump rotation (counter clockwise for the pump in the above picture) while continuing to apply pressure pushing the impeller into the chamber. As you rotate the pulley, the impeller should gradually slide fully into the chamber as shown in the photo below.

    Attachment 517

    To finish the project apply a light coating of gasket sealant on the perimeter of the pump housing using care not to get any of the sealant on the impeller. Install the new gasket and apply a light coat of sealant on the impeller cover. Install the impeller cover and tighten the bolts and you are done!
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    Comments 2 Comments
    1. greenghost39's Avatar
      greenghost39 -
      ive gotten people out of trouble by reversing the impeller and getting a second life out of it ive done it on outboards most of all but the sherwood is much larger pump more meat on it. so out at sea its a trick to get you going and home again. if you don't have a spare
    1. TimG's Avatar
      TimG -
      Never thought of that...
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