1984 Mercury 115 Tach Problems

[sqlightning]

I've got an 84 Mercury 115hp on my boat and the tach does not work. I put a new tach (faria) on it a few weeks back and it worked for a second then stopped working and hasn't worked since. I think i had it on the wrong setting. After I put it on the right setting (12 pole) it is still not working. I check out the rectifier per the seloc manual and it tested bad, so i replaced it with a sierra part. when i went to test it, i just bumped the engine over (not actually started it) and the tach would not move. is it possible having the wrong setting on the tach damaged both the tach and the rectifier? when i hooked it back up, i attached the gray signal wire to each of the yellow wires going to the rectifier and still nothing. does the engine have to actually run to see the tach move, or can it just be bumped over? what else do i need to look at on this?

 

[oldman570]

Re: 1984 Mercury 115 Tach Problems

The motor needs to be running for the tack to get a reading. If the Stator of the motor charging system is bad, the tack will not be able to get a reading. The yellow wires from the stator should read AC voltage when the motor is running and the tack reads this voltage to get a RPM reading of the motor. Testing of the stator and the rectifier can be done by following the trouble shooting guide of the CDI website. The tack is probably not the trouble, and is still in good shape if the motor was not run for a lengthy time. If you moved the gray tack wire to both of the yellow wires on the rectifier and no reading was had , then the trouble will usually be the rectifier or the stator. You will also find that the tack will not return to the 0 reading on the tack when the motor is shut down, witch is normal, and will return to the 0 reading when the ignition switch is turned back on and the motor not running. Test the rectifier first to make sure it is not the fault. It cost less to replace it than replacing the stator, not to mention all the work involved. JMO
Oldman570

 

[sqlightning]

Re: 1984 Mercury 115 Tach Problems

Ok I will check the stator this evening. One thing I noticed is my tach sits below zero all the time. It has been installed on the boat for a few weeks and I have been out quite a bit since I installed it.