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  1. #1
    Registered dhlaw's Avatar
    My Boats:
    2001 Top Gun T/S, 2002 Gladiator
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    Feb 2003
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    New Smyrna Beach, Florida
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    Gaffrig tach question

    I have twin gaffrig tachs and one of them occasionally will jump around (the needle). What would cause this and where should I start to look for the problem?

  2. #2
    Were doomed! Charter Member Wally's Avatar
    My Boats:
    Chris Craft Stinger 222
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    Chicago, IL
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    Some of the older tachs get interference from other electrical sources that may be too close.... I know that Gaffrig has a small circuit board that you can get from them that gets bolted to the back of the tach for this....Give them a call....i may even have one or two sitting around here someplace...i'll check later tonight.
    -Wally


    The dollar decides how far you can go....

    AOL IM: bigblockwally

  3. #3
    Registered User boatinbill's Avatar
    My Boats:
    '99, Formula, 27' Fastech
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    Feb 2002
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    Belleville, IL
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    Hope this will help, I have been told of a problem with grounding can cause this. I have a '99 Formula with an HP500EFI, supposedly they painted the block and then put the distributor on. This caused a grounding problem at teh distributor that only shows up on the tach (boat runs fine), doing exactly what you indicated, jumping around (200-500rpm) occassionaly.

  4. #4
    Were doomed! Charter Member Wally's Avatar
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    Chris Craft Stinger 222
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    I found one filter if ya want it....
    -Wally


    The dollar decides how far you can go....

    AOL IM: bigblockwally

  5. #5
    Registered
    Join Date
    Jan 2001
    Location
    ST. Louis, MO, USA
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    1,658
    Bouncing tachs are usually due to secondary ignition problems. Moisture, bad cap/rotor, bad plugs or wires. You will occasionally see a bouncing tach before noticable engine problems.
    Do the simple stuff first, ie plugs and wires.
    Gary


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