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  1. #1
    Join Date
    Jul 2010
    Pearland, TX

    Default Water Pressure Sensor 2005 5.0 L

    Hello All,

    I'm new to this forum. I hope you guys can steer me in the right direction. I have 2005 Mercruiser Alpha 5.0 MPI. I was on the lake and the Low water pressure alarm began sounding twice every couple of minutes. The pressure was showing 0.0psi. (It should be noted that I ran through some shallow water and churned up some mud and silt.) I flushed the engine and cleaned the sensor. I also flushed for a few minutes with the sensor removed from the power steering cooler. The sensor still registered 0psi. I replaced the sensor with a new one and cleaned the connections (which had a slight green corrosion to it). After all that the new sensor registered .7psi in Idle and up to 2psi at 2500rpm. (all this was done with the muffs on). Since the water temp never gets above 158 deg. I've got to think that my impeller is Ok and supplying sufficient water. Any ideas as to what I'm missing or what to check next. Also, shouldn't there be screens on the raw water intake? I feel certain that my last boat did have screens.

    Thanks for any help,


  2. #2
    Join Date
    Sep 2008
    Maryland - USA

    Default Re: Water Pressure Sensor

    The screens that protect the raw water pump are usually called strainers. yes, they should be there. That said, they won't help a bit with mud and silt.

    Your pressures seem a bit low - taken from the scan tool? I'd be inclined to use a gauge to check to values as it is possible you received a bad (or wrong) sensor. You may also want to check pressure in a couple different places.

  3. #3
    Join Date
    Jul 2008
    , sc,

    Default Re: Water Pressure Sensor

    Check the pressure with the boat in the water - it will vary from just the hose and muffs. And if it's the original impeller replace it - 5 years is 2-3 over recommended, especially if you are in silty water.

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