help with trim gauge replacement please, a one way diode on back of gauge???

I need help finding out info on what I was told was a one way diode connecting the ignition post to the sensor post ? This is on a 1986 VRO 60hp Johnson outboard on a 16 foot aluminum Duracraft. There are two 3 wire cables that come from the throttle control and appear to connect under the dash. The original outboard was an Evinrude 60hp. Have two other 2 wire cables (white-ignition, brown-sensor), one goes to tachometer and it works, the other to trim that doesn't have power to the white wire. Can I power it from the tachometer ignition source?

I recommend that you post this question on the Johnson/Evinrude forum on this site. Go to the top of this page and click on "Forum Home", on the right side, then select the Johnson/Evinrude forum.