my tacho not working stuck at 7000+ rpm

[vcreation]

I got a 95 Yamaha 70 hp, it has the traditional tacho.

when I put my key in, tacho shows 0 rpm (in both on and off position)
but as soon as the engine starts, it jumps to over 7000-rpm and stays there. no matter what happens the tacho is at 7000+ rpm if the engine is running.

PS. the engine runs completely fine not over-revving.

I've replaced the CDI and done the wiring and still the same, could be something short-circuit or something ?

[99yam40]

why was CDI replaced?
I thought the tach signal for that motor is from charging system.

I think you have a problem with tach

Have no idea what tach you have but here is something from Faria on tach problems http://faria-instruments.com/site_ma...achometers.pdf

[robert graham]

Check the wiring and terminals on back of tachometer for corrosion, loose or improper connections....