New Tachometer not working
 

I just installed my new dash and have all my gauges hooked up except for my 2 temp gauges. I had an OMC 4 wire tach for my Johnson 225 oceanrunner. I replaced this with a Faria unit and adjusted the pul/rev setting to 6, the same as the OMC tach. I wired up the new tach and after the ignition is turned on the tach needle just slowly climbs whether the motor is running or not. Ive tried switching around the signal wires as a shot in the dark, same result... Anyone seen this before?

black to ground, purple to ignition, grey to signal, if you have a light blue, it goes to the light

my ignition wires consist of 2 black, 2 purple, one grey... I've wired everything up they way IT SHOULD BE, no go. the tach still does the same thing! wtf!? a little lost here. on the bright side all my other gauges work great and the new wiring job looks like an MIT senior thesis project! whats going on???

i have hooked the tach directly at the engine, bypass the wiring harness, to eliminate some varibles. if it works , then the problem is in the wiring, if not, either sending unit or tach itself.

check to see if your engine is charging while running, the tach takes a signal off the voltage regulator, if the tach isn't working, I check the charging system