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Gaffrig tach question

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Old 03-26-2003, 10:50 AM
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Default 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?
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Old 03-26-2003, 10:57 AM
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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.
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Old 03-26-2003, 11:02 AM
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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.
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Old 03-27-2003, 09:02 AM
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I found one filter if ya want it....
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Old 03-27-2003, 09:08 AM
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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.
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