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Bearing noise or belt slipping?-gctid391601

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    Bearing noise or belt slipping?-gctid391601

    Hello All;

    Just took my 2008 175 (3.0 Liter Mercruiser I/B) out for a lap around the lake to confirm all is well and I could hear an intermittent whining noise - loud enough to hear at planing/medium-cruise speed. I got the boat back to the dock and removed the engine cover. I believe I have narrowed the location down to the alternator. I recorded the sound on my iPhone and am looking for some advice on what it might be. I can't upload an audio file here so I uploaded it to youtube (30 second audio file). Not exactly professional-grade audio recording but is probably better than for me to try to describe it. The iPhone was held close to the front of the alternator to get this recording. The sound is present (intermittently) at all engine speeds.

    http://www.youtube.com/watch?v=tPyOj0jLVCM&feature=plcp

    Any help would be appreciated,

    Thanks

    #2
    Not sure but it sounds like a bearing squeek to me. Belt squeeks tend to be of a higher pitch.

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      #3
      That's kinda what I was thinking too - the belt appears to be correctly tensioned and isn't getting shiny from slipping and the noise does not change with engine speed, which I would expect if it was the belt slipping.

      Now, the next question; impending failure? Should I change the alternator or is some bearing noise acceptable?

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        #4
        I agree, sounds like intermittent bearing noise. I'd change the alternator before running the boat much more.
        1990 2755 - sold
        2005 275 - sold (now boatless)

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          #5
          Change it out, i hear this all the time at work. Eventually it will seize due to overheating and cause more problems.

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            #6
            You can get a mechanic's stethoscope for less than 10 bucks at any auto parts store. That should tell for sure if it's a bearing.

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              #7
              Kåre L wrote:
              You can get a mechanic's stethoscope for less than 10 bucks at any auto parts store. That should tell for sure if it's a bearing.
              Yep, or put one end of a screw driver near the bearing and your ear near the handle of the screwdriver and listen for the sound.

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