Tach ?

[5150abf]

Can't get a tach to work on my motor,1981 Evunrude 50.
Jumped the leads directly to the motor(grey sender and ground wire).
The tach will power on, the needle raises and it will move to @ 1000-1500 while you are on the starter but when the engine starts then it drops back to O.
I have read somehting about the rectifier being involved but the battery will charge at @14 volts so it is good.
Any thoughts?

 

[V1 Rotate]

Re: Tach ?

put the black wire directly to the battery negative and try it there. That believe it or not fixed my tach doing the same thing as yours is doing.

 

[HighTrim]

Re: Tach ?

If your tach doesnt work test the rectifier.

To test the rectifier.....

Place meter in Hi ohms position

1. Disconnect rectifier lead from terminal block. Connect one ohmmeter lead to either yellow or yellow grey rectifier lead, and other meter lead to ground. Note reading

2. Reverse leads, and note reading. Infinite or very high reading in both checks indicates diode open. zero reading in both checks indicates diode is shorted. Normal diode will show a reading in one direction and no reading in other.

3. Repeat with other rectifier yellow lead.

4. Repeat test, connect meter between rectifier yellow lead and rect red/purple lead. Between yellow/gray stripe rectifier lead and rect red/purple lead.