Maybe the boat originally had a special tach that ran off that line. You
bought a generic one.

"Joey916" wrote in message
oups.com...
Ah, hell with it. I just wired in the negative side of the coil to the
gray wire and fired it up. Works like a champ. I still think the Ign
Mod is bad, but they want $275 for one. I guess when it goes bad I'll
install a better ign system and be done with it.