what sends the analog tack signal on a mefi system? lost signal on grey wire.

Its not an analog signal (its on/off signal, sort of digital) but it would come from the ECM. How it get there depends on which motor (serial number)

its a crusader mefi 4 i believe. It has no distributor individual coils 8.1 has same old style engine plug as merc can't get a signal when testing grey wire at engine plug. tack just stopped one day. has computer that plug in the front not the sides. any help would be appreciated

MEFI's

Crusader 8.1 uses MEFI 4.
its a digital signal from the ecm to the boat harness in the gray wire. Disconnect the gray wire from the tach and test the wire in the boat harness and on the engine harness.