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    Speedometer Stopped Working

    My speedo stopped working at the end of last season. Does anyone know how to clean out the tube?

    #2
    Disconnect the tube at the back of the speedometer and blow compressed air into it. This will clear anything in the hose or pitot.
    Gibraltar, Mi.
    1986- 3870- Hino 175's - Just purchased May ,2017
    34' Tollycraft- sold
    88 26' Shamrock/ Diesel
    14' Zodiac Bay Runner

    Comment


      #3
      For a more accurate reading, if you have a smart phone, download one of many free gps based speedo apps.
      Doug
      Hanging Loose
      98 Carver 350 Mariner
      2013-
      KRUSTY KRAB
      2001 305
      5.7 BII
      2006-2013

      Comment


      • Nickdixon
        Nickdixon commented
        Editing a comment
        Works in no current for speed over water and speed over ground. With current, say in a fast moving river or a tide, gps is no good for speed over water.

      #4
      I’d agree with Doug on gps speed. I guess if your in a go fast you may want to know your speed through the water. However the cruiser guys are more interested in the ETA to a specific destination via gps speed. Personally I think the pitot tube speedo is inaccurate for either.
      Dave
      Edmonds, WA
      "THE FIX"
      '93 2556 5.7 Bravo II 2.0:1 18 1/4x19 P
      (.030 over-Vortec top end-part closed cooled)
      The rebuild of my 2556 https://www.baylinerownersclub.org/f...76?view=thread
      Misc. projects thread
      https://www.baylinerownersclub.org/f...56-gctid789773

      Comment


        #5
        For clarification, a typical boat speedometer operates from a pitot tube. Similar to an airspeed indicator on a plane a boat speedometer will indicate the same speed for a given power/loading/trim condition no matter if the boat is going upstream (headwind) or downstream (tailwind). The GPS indicates ground speed and that speed will definitely change according to the speed of the water- slower upstream, faster downstream. Thus if your boat is headed upstream into a 5 kt. current and you power up until the boat speedometer indicates 25 kts the GPS will indicate a 20 kt ground (water) speed. Maintaining the same throttle setting you make a U turn, now headed downstream the boat speedometer will still show 25 kts but the GPS will now indicate a 30 kt ground speed.
        Jim Gandee
        1989 3888
        Hino 175's
        Fire Escape
        Fyrflyer@ca.rr.com

        Comment


          #6
          Thanks Sunbird I will do that today!

          Comment


            #7
            Downsouth,
            I apologise, I should have related this story to you. Not sure what type boat, drive you have but go easy with the compressed air. My buddies speedo stopped working on his dual mercruiser outdrive boat. The pitot is a small hole in the outdrive leg just below the cavitation plate, IIRC. Seems he had hit some wood and that Wood was embedded into the pitot hole. No amount of compressed air was going to clear that. I suggest you check the pitot itself before using compressed air to verify you couldn’t manually clear any obstruction. Should be an easy fix. Good luck!
            Jim Gandee
            1989 3888
            Hino 175's
            Fire Escape
            Fyrflyer@ca.rr.com

            Comment


              #8
              Got it fixed. Turns out there was a hole in the hose on the backside of the motor. There was enough slack to cut out the bad part and reattach the hose. I blew the line out while I had it apart. Thanks guys!

              Comment


                #9
                What side of the motor would that be on? I'm chasing my tail trying to find out why my speedo isn't working either. I think it's fed GPS and since the plotter display is reading speed accurately this might be my boat's problem as well.

                Comment


                • Nickdixon
                  Nickdixon commented
                  Editing a comment
                  I’m sure all of us would prefer that our pitot based speedo worked all the time and if you are doing water sports where a participant is particular about their speed over water because of wake height or other preferences, a pitot based speedo is essential. If your only use is for navigation, the GPS reading on your plotter is what you need. I don’t tow picky wakeboarders, skiers, etc. so I don’t even bother to keep the pitot speedo working since I boat in areas with a lot of debris, which clog the tube up pretty regularly. Now, with no current, there should be no difference in GPS and pitot readings. If you are in a river or an area with significant tidal flows, the difference in readings will be the speed of the current due to either river flow or tidal flow. Currently (no pun intended) my main interest is GPS for navigation but at one time I drove for competitive trick and slalom skiers and the speed over water was critical. In that case only a pitot based speedo was appropriate. In fact we had two speedos and a human with a stopwatch to verify time between buoys.

                #10
                Originally posted by Valhalla View Post
                What side of the motor would that be on? I'm chasing my tail trying to find out why my speedo isn't working either. I think it's fed GPS and since the plotter display is reading speed accurately this might be my boat's problem as well.
                What model & power package? If Mercruiser sterndrive the hose connects to the lower unit dead center & comes through the transom just below the steering arm.
                Dave
                Edmonds, WA
                "THE FIX"
                '93 2556 5.7 Bravo II 2.0:1 18 1/4x19 P
                (.030 over-Vortec top end-part closed cooled)
                The rebuild of my 2556 https://www.baylinerownersclub.org/f...76?view=thread
                Misc. projects thread
                https://www.baylinerownersclub.org/f...56-gctid789773

                Comment


                  #11
                  It's a Mercruiser but I don't know what package it may have. Are you talking about displacement? If so, I believe it is 496 inches. It says HO on the motor. Is that the power package?

                  Comment


                    #12
                    Originally posted by Valhalla View Post
                    It's a Mercruiser but I don't know what package it may have. Are you talking about displacement? If so, I believe it is 496 inches. It says HO on the motor. Is that the power package?
                    Mercruiser, see Nickdixons comment above
                    Dave
                    Edmonds, WA
                    "THE FIX"
                    '93 2556 5.7 Bravo II 2.0:1 18 1/4x19 P
                    (.030 over-Vortec top end-part closed cooled)
                    The rebuild of my 2556 https://www.baylinerownersclub.org/f...76?view=thread
                    Misc. projects thread
                    https://www.baylinerownersclub.org/f...56-gctid789773

                    Comment


                      #13
                      I'm not quite getting it. Is there a pitot static system on a boat? I'm no ECS engineer but I do remember how a Prandtl tube works from school. Where is this pitot port located?

                      Comment


                      • builderdude
                        builderdude commented
                        Editing a comment
                        See link below

                      #14
                      http://www.mariahownersclub.com/foru...wide-open.html
                      Dave
                      Edmonds, WA
                      "THE FIX"
                      '93 2556 5.7 Bravo II 2.0:1 18 1/4x19 P
                      (.030 over-Vortec top end-part closed cooled)
                      The rebuild of my 2556 https://www.baylinerownersclub.org/f...76?view=thread
                      Misc. projects thread
                      https://www.baylinerownersclub.org/f...56-gctid789773

                      Comment


                        #15
                        Thanks - Will have to have my mechanic look at it.

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