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  1. #1

    pro 785 tach not working

    Just bought a 1998 pro 785, I think the mfd was replaced not too long ago, only shows 4.2 hrs. Everything works except the tachometer. it just shows all zeros all the time. I wouldn't worry about it but I can only get the ski up to 49 mph and need to rule out either rpms or pump. Anybody got any pointers on why its not working???

    Its an awesome ski, the power band isn't very smooth, doesn't like going below 30 but it rips pretty hard.


  2. #2
    ph2ocraft's Avatar
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    I think I'd be more interested in the engine compression with 49 MPH and a rough feel, make sure the engine's O.K. first.
    Oh and WELCOME to the Green Hulk Forums!!

  3. #3
    The engine runs and sounds real strong but I'll throw the compression gauge on it tomorrow. It loads up at idle so im sure it needs a tune up. I still need to get the tach fixed though. The pump has been messed with. has a chewed up 5 vane stator on it right now, Not sure of the impeller, I think I might be losing some mph back there though

  4. #4
    100 MILES OF HEAVEN AND I AM SMACK IN THE MIDDLE KEYZBUM's Avatar
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    Yo Daddy
    WELCOME TO THE FORUM
    49 mph??? is that gps or the mfd(dream-o-meter)witch i find works great as a trim/fuel/oil gauge but for mph and rpm forget it
    try a gps and a tiny tack or pet tach for speed and rpm..
    Ya got to love the 3 speeds of a pro ----just above idle --oh crap hold on---and my cheeks are starting to flap around
    enjoy this place, people and info here are the best
    1 more thing got any pics
    mattman

  5. #5
    Actually, in my experience, the tachs on the Pro MFDs are pretting accurate, as are the speedos. I know this isn't true of most skis, but with all 4 Pros I've owned, the accuracy has been pretty good.

  6. #6
    Guess this isn't a real common problem?

  7. #7
    ph2ocraft's Avatar
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    When you accelerate do the exhaust valves move?
    If not, maybe the CDI is bad and not throwing a tach and exhaust valve signal??

  8. #8
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by wrenchdaddy View Post
    Just bought a 1998 Pro 785, I think the MFD was replaced not too long ago, only shows 4.2 hrs. Everything works except the tachometer. it just shows all zeros all the time. I wouldn't worry about it but I can only get the ski up to 49 mph and need to rule out either rpms or pump. Anybody got any pointers on why its not working???

    Its an awesome ski, the power band isn't very smooth, doesn't like going below 30 but it rips pretty hard.
    Welcome to the Green Hulk!

    Those MFD displays are known to self reset the engine hours. Typically associated with the battery being removed, or dead, for a long time, or a bouncy electrical contact while the battery was being hooked up.

    It sounds like the yellow wire from the electrical stator is not connected to the MFD (or the MFD is bad). The Yellow wire also provides the alternator current for battery charging, via the LR voltage regulator. Check the battery charging voltage with a multi-meter (at the battery posts), and check the routing of the Yellow wire to the MFD. Check for corrosion and poor contacts at the MFD connector.

    You can try an MFD reset.

    If you have not done so already, download the 1992-1998 Service manual, and the Pro785 supplement.

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