ignition problem with my 455

[1975 sanger 455]

i just put a new tach and plugs in my boat and now it doesnt want to get any spark. i did gap the plugs to spec .060. when i re-wired the tach however i ran new line and left the old line in place. does that line need to be connected to anything in order for the distributor/ coil to be activated?

[DelawareDave]

.060 gap? Are you running HEI? There should be a tach terminal on the dist cap of an HEI, and a terminal for a 12 volt hot wire from the ign switch. The wire should go directly to the tach terminal on the gauge. The gauge also has a positive (12v) and a negative terminal that must be hooked up.
If you have a regular ignition coil, the tach wire would go to the negative side of the coil.