Tachometer fault 60efi 4 stroke bigfoot

[Matan]

My tachometer has stopped working. But yesterday during a good run it came back and worked for a while. Then stopped again. Like perhaps a loose sender? Where is the sender? I would like to check the connections.

[boats.net]

Check for key on voltage between purple and black wire at tach, should be 12 volts with key on. Gray wire is signal wire from voltage regulator, need a peak reading voltmeter to test voltage when engine is running, voltage should increase as rpm's increase.