Tach not working on my 125 Mercury

[BOAT DOCTOR]

This motor is nothing but problems. First it lost fire couldn't figure it out so said f it and bought almost a whole new electrical system. Stator, rectifier,and regulator brand new side box and main harness and guage harness coming from box all new turn key motor runs great battery charging all is good then my tach stops working so bought a new tach still does not read any rpms the tach needle will zero out when key is on but still reads nothing don't have any idea where to go next could somebody maybe point me in a direction i would greatly appreciated thanks

 

[Georgesalmon]

What year motor? The tach signal comes from the stator. On many motors the stator wires are yellow and the tach signal comes from one of those wires where they are connected to the AC side of the rectifier. If all the electrical was replaced maybe that wire was not connected. We know the stator is good as you say it is charging the battery. The wire is usually gray or on some older motors it can be tan.

 

[gm280]

I agree with George above. You could even have a problemed wire from the engine to the tach. So you have to check the connection at the engine side, but also at the tach end and even make certain the wire is good from those two places.

And one other thing. In the future, instead of just buy all new everything, why not troubleshoot the problem and replace just the defective part. Buying new does not fix things some times, as you presently see. Learn some basic troubleshooting techniques and save a lot of money for other things. In fact I would start by swapping out teh ignition parts with the old ones to see what was the problem. Then you will also verify the old good parts for furture needs if needed. JMHO!

 

[BOAT DOCTOR]

Don't no the year but serial number is 0g050539 If that would help the stator has 2 yellow wires running to a rectifier mounted on carbs and from there to a another 3 post rectifier by switchbox also has another two yellow wires coming from stator to the three post rectifier don't no if it is wired right on the 3 post rectifier any one no where to find a wiring diagram

 

[BOAT DOCTOR]

Got the tach reading but it bounces like a basket ball what could be some causes of that situation ran a ground from the batt to the guage didn't make no difference any help I would appreciate thanks