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  1. #1

    Default Losing Fresh Water from the pump

    I am losing a gallon+ of water every few hours of operation on one of my two DD 671s. I see a strong drip coming from the water pump, so that is probably the source.

    Can I install a used or rebuilt pump?

    Is the pump replacement a complex job? Could a moderately qualified "mechanic" and boat owner do it himself? There is quite a lot of room between the engines, so it would be a comfortable work environment. (as opposed to oil pan replacement).

    Larry

  2. #2
    Join Date
    May 2015
    Location
    Oregon
    Posts
    72

    Default Re: Losing Fresh Water from the pump

    There are two pumps on each engine, one in front of the blower and one usually on the back of the engine. The blower pump is coolant, the back one is raw water.
    Either could be changeable by someone with some mechanical ability and common tools. I figured it out when I was 13. The front pump should have a coolant drain. The rear pump usually is above the water line and cracking the outlet will let the water drain out the seacock (if it's open). There should be a zinc in the raw water pump and removing that will also let the water out. Good time to replace all engine zincs. I get mine here: http://www.zincwarehouse.com/engine-pencil-zincs.html Much cheaper than marine stores - about $3.
    Depending on how old the engines are, there are two different styles raw water pumps. The old style have mostly been replaced. They commonly leaked and used brass/bronze gears and two shafts. The modern style uses an impeller and has an enclosed single shaft. All the pumps can be rebuilt and there are kits available.
    Most likely, the shaft seal is failing. They fail with age or use. When I buy a boat, one of the first things I do is replace all the shaft shaft seals.
    If I were you, I would buy a service/overhaul manual. They're often on Ebay. Most, if not all of the maintenance can be done by a careful owner.
    If you're near a big city, a bearing supply should have the seals. Also online.
    Ebay often has new/used pumps and is a good place for spares. I have 2 671s and carry spare pumps. If you get a manual, you will see, with some additional tools (drivers), you can rebuild the pumps without power equipment.
    If you have turbo equipped engines (671TI, etc) you need high volume coolant pumps. Use a new o-ring if replacing the coolant pump. Buy new gaskets in any event.

  3. #3
    Join Date
    Nov 2009
    Location
    temecula, ca., usa
    Posts
    2,674

    Default Re: Losing Fresh Water from the pump

    Nothing real complicated about changing the fresh water pump. And, as stated above the shaft seal is probably all that needs to be replaced. However, the part of the shaft that the seal lip rides on can get grooved so that needs to be assessed for wear. The pump being gear driven also uses an oil seal and changing that when the coolant seal is done is good practice. Or just get a rebuilt pump and bolt her on.
    Good luck.

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