1977 70hp Evinrude - Tach wire hot?

[cougar15]

Hi, this is my first season with a boat (it's a hand me down from my borther) and I'm trying to do some upgrading. The boat currently does not have a tach and I would like to add one but before I spend the money I was wondering if there is any way to check if the gray lead in the control box is actually connected to anything? According to the shop manual the gray wire is the impulse lead for the tach but since this boat never had a tach, I don't know if it is connected to anything at the motor. Does anyone know of a way to test the connection short of buying a gauge and hooking it up?

 

[Barnacle_Bill]

Re: 1977 70hp Evinrude - Tach wire hot?

The gray wire normally goes to the yellow/gray wire from the stator. Connection is usually made at the rectifier. In your case I believe its at a teminal strip.

 

[Uniflite32]

Re: 1977 70hp Evinrude - Tach wire hot?

I just went through this with my 1973 65 HP 'rude. The gray wire is connected back at the motor. I connected the gray wire in the control box to my "send" on the tach and connected a power wire to the purple wire on the ignition switch and it seems to work fine. I'm running a Teleflex tach.

 

[rickdb1boat]

Re: 1977 70hp Evinrude - Tach wire hot?

You should be able to pick up 3-4 volts on the send wire at idle speed, if the rectifier is good(Charging system working). A bit more at higher RPMs....Tach should also zero when you turn the key to the ON position....