1988 Mercury Classic 50 Tach wiring

I have a 1988 Merc classic 50 45HP engine. I want to install a Sierra Tachometer. The tach is supposed to work on an outboard. I tried some ways to wire the sensor wire to the motor but none work. I also played with the setting on the tach. I am told to wire it to one of the posts on the rectifier/regulator, but that doesn't seem to work. There is also a 5 pin plug with an external brown wire on my control module. I tried wiring to the brown lead which is what the wiring diagram shows and it doesn't work either. Any suggestions????

For some whacky reason, I've seen (twice now) where one of the two yellow wires coming from the stator will not work the tach. I switched to the other yellow wire and away we go.

Have you tried that?

Jeff

PS You need to use the '6P' setting on the tach; and wiggle the adjustment a few times to clean the contacts.

Thanks for the reply. Yes, I have tried that and neither yellow wire worked. I had the tach set on 4P but will move it to the 6P and try it again. I will post the results.
What is the 5 pin plug pigtail on the shift controls? It is about a foot long with a rubber covered 5 pin plug and a brown wire coming out on the outside of the plug. It is located just below the kill switch.

It will be a gray wire to the rectifier,and that five pin plug will take a harness with the correct wire,grey,which goes to the back of the tach.My fear now is that by hooking to the brown wire,you may have cooked the tach.The other wires should be purple = +,black = -,tan/blue = temp sender,brown/white = trim sensor. Brown ?? Pic might help

Thanks for the reply and the good info. Hopefully the tach is OK. I will post a pic of the control tomorrow morning.

bstig60 said:

Thanks for the reply and the good info. Hopefully the tach is OK. I will post a pic of the control tomorrow morning.

Click to expand...

Heres some pics of the shift control module.

http://www.boatwire.info/images/remotes/rem_mercury.gif Here's a link to your remotes.The tan or brown wire is for temp.gauge. A link to what the wire colour is for http://www.maxrules.com/fixmercwiringcodes.html .
This is what you need to connect to that socket,for illustration purposes only,I do not know the seller or have any connection with them. http://www.ebay.com/itm/NOS-Mercury...g-Harness-Assembly-A-84-86396A4-/111799894343

Thank you. This is very helpful. It makes a big difference knowing what control box I have installed on the boat. I ordered the NOS pigtail wiring harness. At least I will know the wiring is correct for the tach and I can add the other gauges if I decide to. That will also give me switched battery for the tach and other gauges I might add.