No voltage jump while running, tach not working 81 Johnson 90

[smoedog]

I have a 81 Johnson 90 I just put on my pontoon. Everything runs good. Only real issue is my tachometer does not work, and im not getting a voltage jump from my battery while running.

First off about the voltage. Reading straight off the battery without the motor running. I get 12.8v With the motor idling I get 12.9v. Voltage does not go up with increase of RPM.

Second my tachometer does not work. I had a force 50 on this pontoon and replaced it with this Johnson. The tach has not worked since. No I have not messed with the settings dial on back as I do not know the correct setting. But I have checked continuity from the back of the tach to the grey wire on my terminal board which is fed by the rectifier.

Now I am leaning towards a bad rectifier and am planning on replacing it with a 25a bridge rectifier. Before I do this, is there anything else I should check?

 

[durban]

the tach is gov-end by the pulses from the sensors in the trigger your charging issue i would suspect a faulty rectifier cdi has got info to check it between the 3 wires .

 

[smoedog]

According to this wiring diagram and how my boat is wired up, the tach pickup taps off the rectifier.

http://www.maxrules.com/graphics/omc/wiring/80_81_V4.jpg

So I dunno. How is one to go about testing the rectifier or make sure its getting propper AC voltage.

 

[emdsapmgr]

The fact that the tach does not work and that the voltage does not increase after running for a while indicates that the rectifier is shot. Just replace it. A new one should fix both problems.