Tach wiring

[kendallgriffin]

My multifunction tach LCD went out on my 2000 150vmax 2 stroke. Friend gave me tach he had lying around that worked fine. My original tach was the one in ordinal pic. Hooked up new tach and doesn't turn on. New tach had same wires but also an extra purple and black. Don't know why it won't power up

[rodbolt17]

Yamaha does not use purple as any wire color or function.
is this gimmie freebie an actual Yamaha tach?

[kendallgriffin]

Sorry' I am color blind. It appears to be purple or lavender. May be a blue color for all I know. It does say yamaha in it. The wires are in two groups. The colors I mentioned in the picture attached and the two other wires are black and that blue/purple color