Dead Tach and How to Test

[Blu_Lunch]

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

[reelapeelin]

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 ;) ....

[macojoe]

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

[Blu_Lunch]

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

[TheTinMan]

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.

[TheTinMan]

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

[Blu_Lunch]

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

[bigshrimpin]

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

[Blu_Lunch]

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?

[Blu_Lunch]

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 * * *

[reelapeelin]

Thanks Blu...didn't know my tach wired outta the control ;) :D...the things ya find out on this board!! ;) 8) ...