Mercruiser 5.0 MPI WATER PSI QUESTION

Discussion in 'General Maintenance/Repair Questions' started by Madifonzo, Oct 19, 2013.

  1. Madifonzo

    Madifonzo New Member

    716
    Sep 30, 2013
    Boston, Ma
    2005 280
    Zodiac Zoom 310 9.9 Honda
    Twin 5.0 MPI with Bravo III Drives
    I was out today for a little run. I was toggling through the displays on my smartcraft gauges. What I came across was a little strange. Port engine was reading around 30 PSI and the starboard was reading 3-4 PSI. NO alarms were going off or anything. The pressure did not equalize at idle or at cruise speed. My instincts are telling me that a pressure sensor may be faulty or a guage issue. I would assume that if the water pressure was really that low that engine would a lot hotter than the other or possibly over heat but the temps were right where they are normally. Any input would be great. Also can anyone tell me where the pressure sensors are? Shouldn't the alarm be going off for low pressure?

    Not sure if it's relevant but the engines are FWC on the block side only.

    Another "Issue" I noticed today was that the sea temp on smartcraft was reading 100 degrees or more. I am assuming that the sensor should be reading the actual sea temp which is around 60 in my area. Does anyone know where that ses sort is located?

    thanks for any feedback or direction.

    after reading some other forums I am getting the impression that I may be wrong on which engine may have the issue. So with that said what is the running psi of other 5.0's out there?
     
    Last edited: Oct 19, 2013
  2. matthewmiller01

    matthewmiller01 New Member

    May 14, 2008
    Knoxville, TN
    2008 290 Sundancer
    Twin 5.0 MPIs (DTS) w/ Bravo III Drives
    Kohler 5 ECD
  3. tbirdvet

    tbirdvet Active Member

    Sep 24, 2009
    Michigan
    Previous boat: 2008 330 Sundancer
    Vetus Bow Thruster
    Kohler Gen.
    Twin 496 MAG, 375HP Bravo III,
    I had the same issue. It was a faulty sensor.
     
  4. Madifonzo

    Madifonzo New Member

    716
    Sep 30, 2013
    Boston, Ma
    2005 280
    Zodiac Zoom 310 9.9 Honda
    Twin 5.0 MPI with Bravo III Drives
    So am I correct that the engine showing really high psi has the faulty sensor? From what I am reading water psi should be anywhere from 5-17 psi depending in throttle position. I was wondering why the sensor wasn't going off but I guess why would it for pressure too high. If I knew where the sensors were I would just switch them from one engine to another and see of the problem persists.
     
  5. matthewmiller01

    matthewmiller01 New Member

    May 14, 2008
    Knoxville, TN
    2008 290 Sundancer
    Twin 5.0 MPIs (DTS) w/ Bravo III Drives
    Kohler 5 ECD
    The sensor is on the aft end of the engine toward the STBD (left when looking aft) on a rail going athwart ships. Leaning over the engine, you will see the sensor with two wires coming off the top.
     
  6. Madifonzo

    Madifonzo New Member

    716
    Sep 30, 2013
    Boston, Ma
    2005 280
    Zodiac Zoom 310 9.9 Honda
    Twin 5.0 MPI with Bravo III Drives
    Thanks for the info. Can you confirm the proper running psi? I am trying to figure out which engine has the problem. Port engine was running at 30 psi and fluctuated slightly based on throttle. Starboard engine was running at less than 10 and varied based on throttle.
     
  7. jason78

    jason78 Active Member TECHNICAL Contributor

    Sep 3, 2008
    Fort Mill, SC / Lake Wylie
    1997 20 Outrage
    200 Merc Offshore
    If you can include the approximate RPM you are seeing these PSI readings at, it would be helpful.
     
  8. Madifonzo

    Madifonzo New Member

    716
    Sep 30, 2013
    Boston, Ma
    2005 280
    Zodiac Zoom 310 9.9 Honda
    Twin 5.0 MPI with Bravo III Drives
    Went down to the boat today to confirm issue and see if I could locate WP sensors on engine. I ran engines at idle to operating temp. During the warm up the idle was at 600 RPM +/- and the port engine showed 30 PSI while the starboard was at around 1.7 PSI. Brought throttles up to around 1100 RPM. Port engine remained at 30 PSI and the starboard engine increased slightly to around 3 PSI. I was also not able to locate the WP sensors. Engine temps are constant at around 160 degrees, just as it should be.
     
  9. Bucit

    Bucit New Member

    Mar 12, 2010
    St. Petersburg Florida
    2005 280 Sundancer
    2004 SPD-104 Achilles w/ 8hp Yamaha
    Twin 4.3 MPI's with Alpha drives.
    I have a 2005 with the Smartcraft guages and I don't get water pressure on the digital read out (only the analog guages) when I scroll through. I don't get water temp either? I would figure all 2005's with SM gauges should read the same things right?
     
  10. ZZ13

    ZZ13 Well-Known Member GOLD Sponsor

    Nov 25, 2009
    Lady's Island, SC
    2001 400 Sedan Bridge
    Cummins 450 Diamond
    The screens displayed is configurable using the CAL1 selection. There are smartcraft manuals all over the Internet if you don't already have one.
     
  11. matthewmiller01

    matthewmiller01 New Member

    May 14, 2008
    Knoxville, TN
    2008 290 Sundancer
    Twin 5.0 MPIs (DTS) w/ Bravo III Drives
    Kohler 5 ECD
    Unfortunately, I can't. I am still looking for the right answer.

    In my post (linked), I have listed the RPMs and water pressures for each.
     
  12. jason78

    jason78 Active Member TECHNICAL Contributor

    Sep 3, 2008
    Fort Mill, SC / Lake Wylie
    1997 20 Outrage
    200 Merc Offshore
    Well I can definitely tell you 30PSI at idle is too high and abnormal. At idle I am about 1.2-1.7 PSI, heck, even at 4100 I am just under 20 PSI. Either you have some sort of blockage causing an abnormally high pressure in the power steering cooler (location of the sensor) or a bad sensor. My guess would be the latter, especially if it is showing 30.0 flat. That is probably the end high range for that sensor and it has failed at full. One thing you can do is swap the port and starboard sensors and see if the high PSI follows the sensor. If it does, replace the sensor.

    I will try to find you a picture of the PSI sensor.
     
  13. jason78

    jason78 Active Member TECHNICAL Contributor

    Sep 3, 2008
    Fort Mill, SC / Lake Wylie
    1997 20 Outrage
    200 Merc Offshore
    The Sea Temp reading is relayed to the Smartcraft system from the depth transducer located between the stringers in the forward portion of the bilge. There is a widely known problem where the temperature portion of the transducer fails and it reads some crazy high or low reading. That is probably the case here but it could also be caused by bad Smartcraft configuration. The transducer is connected to the Starboard engine so you will need to go to CAL2 in the Port tach and make sure the Sea Temp sensor is turned off or this could cause the issue you are describing. You will also need to do the same on the Starboard tach and make sure that sensor is ON. I will try to find some instructions here and post them. This can also be found in the SC owners guide. You should be able to follow the wire up from the transducer to the top front of the engine where it plugs in to the "DIAGNOSTIC" plug. This should be easy to find. Make sure this is plugged in as well. I have heard where someone scanned the ECM and never plugged the transducer back in. Does the depth work?
     
  14. jason78

    jason78 Active Member TECHNICAL Contributor

    Sep 3, 2008
    Fort Mill, SC / Lake Wylie
    1997 20 Outrage
    200 Merc Offshore

    OK, I knew it was here somewhere. See the picture in post #7 of the thread below. The H20 sensor is circled in RED. Remember, this picture if taken from the back of the engine. This thread also gives some good advice about troubleshooting the H20 sensor.

    http://clubsearay.com/showthread.php/21295-Water-Pressure-sensor
     
    Last edited: Oct 21, 2013
  15. Madifonzo

    Madifonzo New Member

    716
    Sep 30, 2013
    Boston, Ma
    2005 280
    Zodiac Zoom 310 9.9 Honda
    Twin 5.0 MPI with Bravo III Drives
    Thanks. That is very helpful.
     
  16. Bucit

    Bucit New Member

    Mar 12, 2010
    St. Petersburg Florida
    2005 280 Sundancer
    2004 SPD-104 Achilles w/ 8hp Yamaha
    Twin 4.3 MPI's with Alpha drives.
    Thnaks Bill. I have all the manuals for everything that was installed in my boat. I take a look. I noticed this years ago but figured they were all set up differently.
     

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