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Oil Pressure gauge erratic on 350 mag engine-gctid376812

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    Oil Pressure gauge erratic on 350 mag engine-gctid376812

    I have a 2011 350 mag engine with a bravo III. The engine starts up fine, and the oil pressure shows where it suppose to be. Then as I accelerate after reaching 1800 RPM's and continuing the pressure gauge gets erratic and bounces quickly from 40-80, then straight down to zero, back up to 40, then jumps all over the place again. Then it settles to normal, only to do it again at a later time (which could be in a min, or 5 min...no set time). The engine sounds don't change, nor does the temperature or, tach. No alarms are heard...

    Questions..

    1) IF it was low oil pressure, wouldn't the engine sound different?

    2) Would the alarms sound? (Is the alarm system independent from the oil pressure sensors)

    3) Is it the sending unit or gauge? If so, where is the sending unit located on this type of an engine?

    4) Or can it actually be low oil pressure?

    Thanks as always.

    Mike

    #2
    I'll assume your boat is also a 2011 (please put your boat info in your sig).

    First place to look will be the wiring, then the sender. Your alarm should sound if the pressure is as low as the gauge shows.

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      #3
      boat is a 2011 2855

      that's the thing...the pressure reads zero but there is no alarm.

      Comment


        #4
        I belive the alarm uses a different sensor then the gauge for pressure.

        Comment


          #5
          Hi MikACY, Just went through this on my 350 MPI, BAD sending unit, when i went back and grab hold of it i crushed the outter shell, don't know what boat you have, mine 2452 I had to remove the port side exhaust riser to get to it, replace it ASAP because if the rubber diphram inside fails not only will you have oil everywhere you could loose a motor, Hope yours has the brass extension to get a wrench on it otherwise it could be lots of fun backing it out, Thanks Doug

          Comment


            #6
            MikeACY wrote:
            boat is a 2011 2855

            that's the thing...the pressure reads zero but there is no alarm.
            Your engine should still be under warranty. I would just have it diagnosed and fixed by an authorized Mercruiser mechanic.

            Comment


              #7
              DEK wrote:
              Hi MikACY, Just went through this on my 350 MPI, BAD sending unit, when i went back and grab hold of it i crushed the outter shell, don't know what boat you have, mine 2452 I had to remove the port side exhaust riser to get to it, replace it ASAP because if the rubber diphram inside fails not only will you have oil everywhere you could loose a motor, Hope yours has the brass extension to get a wrench on it otherwise it could be lots of fun backing it out, Thanks Doug
              (note to self- DO NOT piss off this man!)


              Comment


                #8
                jwishart wrote:
                Your engine should still be under warranty. I would just have it diagnosed and fixed by an authorized Mercruiser mechanic.
                Winner Winner- We have a Winner!

                Comment


                  #9
                  I had this exact problem last season. It was corroded gauge wire on the pressure sender. Simply disconnected the wire terminal from the sending unit, cleaned everything with a wire brush and applied some dielectric grease. Problem went away.

                  Comment


                    #10
                    Thanks everyone..

                    Yes it is still under warranty, but I wanted to make sure I didn't screw up the engine by running it this way. I was hoping the low pressure alarm had a different sensor then the one for the gauge...apparently it does?? Also I wanted to take a look at the sensor myself to see for future reference. Does anyone know where the sensor is located on my 350 mag MPI? Someone suggested I had to pull a manifold??

                    Mike

                    Comment


                      #11
                      MikeACY wrote:
                      Thanks everyone..

                      Yes it is still under warranty, but I wanted to make sure I didn't screw up the engine by running it this way. I was hoping the low pressure alarm had a different sensor then the one for the gauge...apparently it does?? Also I wanted to take a look at the sensor myself to see for future reference. Does anyone know where the sensor is located on my 350 mag MPI? Someone suggested I had to pull a manifold??

                      Mike
                      DON'T TOUCH ANYTHING!



                      Let the dealer take care of it. Even if the motor was trashed because of a failed sensor, the warranty would cover it. Now, if you go wrenching on the engine, the dealer could successfully argue that you went in and may (operative word) have damaged something- claim denied. Even if your warranty declined, your vessel insurance would cover it (based on the policy language).

                      Take it to them- give it to them, and let them take care of it.

                      You are correct- usually there will be be a sensor for the gauge (dynamic) and a switch for the alarm (on/off).

                      Comment


                        #12
                        I have the same exact problem on my 2011 Bayliner 285 with a 350 Mag and Bravo III outdrive. Let me know what the resolution was if you found one!

                        I am having the dealer look at it, but honestly they need all the help they can get...

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