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  1. #1
    Join Date
    Jan 2013
    Location
    Juneau WI
    Posts
    17

    Default Bouncing Tach problems

    Have a 1999 Moomba outback LS with a tachometer that is bouncing. I get up to 38 miles an hour and the tachometer starts to bounce around 4200-4300 RPMs. The Bouncing as a range from 4200 to 4700 RPMs. My boat used to do 42 43 mph in no longer does that I feel because of the bouncing tachometer is causing the rev limiter to engage. When tachometer starts to bounce I still have almost 2 inches of throttle left but get no response.
    Any ideas would be greatly appreciated thanks in advance

  2. #2
    Join Date
    May 2009
    Location
    North End Lake Lanier GA
    Posts
    8,155

    Default

    You need a new Tach.
    Not much you can do to stop the bouncing.

    As long as the engine isn't surging the tach should stay steady.


    Sent from my iPhone using Tapatalk
    Malo <--- Means--Evil or Mean One. This explains a lot.
    2013 Mojo 2.5 Skylon Tower. Bestia < Beast >
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  3. #3
    Join Date
    Jan 2013
    Location
    Juneau WI
    Posts
    17

    Default

    Pulled tach out didn't fix speed problem.
    Carb run great up to 38 then dogs
    Anyone help?

  4. #4
    Join Date
    Mar 2003
    Location
    Springfield Missouri
    Posts
    3,391

    Default

    My tach has been doing that for years. I tap the glass until I get the rpm I expect. For real. It is a tach and hour meter and that is it. I suspect your throttle linkage.
    1998 Mobius
    310 HP PCM
    SOLD

  5. #5

    Default

    Check for a new Tach.

  6. #6

    Default

    Your tach doesn't stop the motor from reving up it just reads it.so this won't be your issue. It sounds like a fuel air spark issue possibly, has it thrown any codes? Have you replaced the distributor cap, fuel filter and air filter recently?
    2018 Supra SL550
    2017 Supra SE450

  7. #7
    Join Date
    Jan 2013
    Location
    Juneau WI
    Posts
    17

    Default

    Just put a Acme 475 prop on my boat and got back to 44 mph.
    Also found out after taking the prop I had on my boat back to the shop that worked on the prop that they never worked on that prop.
    Meaning the place that did my carb work switched my prop. causing the tack and speed issue.
    The place that does props stamps the props with a work number. I always said that they switch my prop but could never prove it till now.
    Really if you hit something with a boat you are working on own up to it and fix the problem.
    They have lost my Business forever not to mention my friends Business.

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