2001 150 2 stroke tach problems

[Thirsty Turtle]

So this issue started when I purchased this boat last year. Has a Faria tachometer and would intermittently drop out to zero but the engine would stay running the same. The seller said it has done this for years and has never affected the running of the engine. I dealt with it all last season and have put over a hundred hours on it with no issues. I decided to put a new tachometer in it and noticed a connector was loose under the dash so I changed it and it seemed to fix the problem and did not change the tachometer out but it started dropping out again. Well today I finally decided to put in the new tach and turns it out that was not the problem. I used the green wire out of the harness for the signal and 12 volt and ground. All hooked up the same way and still not working. I did notice with the old tach when it stopped working if I played with the trim switch it would kick on and work. The motor is putting out plenty of voltage when running so I don’t think it is a rectifier issue. Any help would be greatly appreciated. Also it is set on 5 on the back of the tach for 12 poles

 

[99yam40]

bad connection somewhere
might be on the negative/ground side also

the heavy current draw of the T&T motor makes a connection for a little while

 

[Thirsty Turtle]

I will check the voltage with the motor running tomorrow. Checked today with engine off and showed 12.7 volts both on the positive and negative sides of the tach. I checked all the fuses under the cowling and they are good. Pulled the main connector apart and no corrosion was seen. I guess next step is to trace the green wire from the gauge to the power head??