Tach issues!

[TheOtherOne]

Alrighty, I'm back with some more tach issues. I have a 1969 Mercury 80HP. The engine runs great, and the tach worked fine about 5 years ago. It died during this time while it just sat, covered up.<br /><br />My grandfather gave me a tach you just clip to the coil. Trying that, I did get a signal. There's a start. I found the wireing for the engine, so I connected it to the positive being sent to the tach, and just gound it. It worked again, but it was rather weak. It only showed 100RPMs(yes, 2 00, not 1000)<br /><br />I went back to the tach, removed the wires and connected that one my grandfather loaned me. Once again, really low. I tried the old tach and realized it pegged all the way back. I figured the wires could of been reversed. I fliped then around, then just cutting the switch on sent the neddle to 7,000.<br /><br />I'm lost!