Dead Tach and  How to Test
 

I had the trouble where the battery cables got crossed, yesterday I started the 82 merc 150 and had no tach and 12.8 V max output, today I replaced the recifer and it's still the same but the starter didn't disengage end up disconnectimg the battery, jiggled the key switch it's ok now but I still have the same original problem

Re: Dead Tach and Not Charging 82 Merc 150
 

Blu, so the tach was workin' B4 the wires got crossed?...hope it didn't fry :P ... I don't know SQUAT about Mercs (and not much about anything else), but sounds like your alternator ain't pumpin' the juice it oughtta :-/...good luck w/ it and let us know how she go ;) ....

Re: Dead Tach and Not Charging 82 Merc 150
 

I have a Garmin fish finder and it has a volt meter on it, does yours?? Some GPS have them also.

This might tell you if you are charging. I pump 13.8 V from the Yamaha

Re: Dead Tach and Not Charging 82 Merc 150
 

Getting the same voltage on the Lowrance too, the tach was working after the cross..........

Re: Dead Tach and Not Charging 82 Merc 150
 

This may sound stupid but....when the motor is running knock on the glass with your knuckles (you may of tried already). My old boat's tach sometimes would take a little rap to get it goin.

Re: Dead Tach and Not Charging 82 Merc 150
 

Is that 12.8v at idle? That's about what my guage reads until you give a little throttle.

Re: Dead Tach and Not Charging 82 Merc 150
 

I finaly found the Merc sevice manual and got the multitester out I did the stator test it passed but the new rectifer is bad .....back to the dealer

Re: Dead Tach and Not Charging 82 Merc 150
 

That sucks, but you've got it figured out. Sounds like you might need a new key switch too pretty soon.

Re: Dead Tach and  How to Test
 

It never ends I replaced the rectifer and it still was not charging , ran the test from the service manual and THE NEW ONE WAS A FACTORY DUD! The dealer replace the unit with a new new one and now it puts out 13.5 volts at 1500 RPM BUT THE TACH IS STILL DEAD , it was working prior to the old rectifer dying. How do I test the tach with a multimeter?

Re: Dead Tach and  How to Test
 

I found this for checking the tach. *Mine is garbage, I have correct voltage everywhere but it still does not work. *http://ww2.tflx.com/pdf/obtach%7E1.pdf * * *