1973 25hp Johnson how to add a tach and temp gauge?

[Mattwahoo83]

I have a 1973 Johnson/evinrude 25hp Frankenstein motor that I just built with a 1972 evinrude and 1973 Johnson 25hp. The model started as a Johnson 25R73A but I have added the electric start from the 1972. It doesn't have a wiring harness and is a tiller model. I'd like to a tach and temp gauge but don't know where to start. How do I wire the tach and add a temp gauge. Also, what temp should it run at? Thanks in advance

 

[joereeves]

That engine's ignition is a dual coil, dual points magneto system. You will need a tachometer that operates off of one of the point sets. Check with your local dealership for specifics.

The heat gauge is a no brainer, the complete kit should be available at any dealership, comes with a "L" bracket that attaches to a head bolt. The other end of that "L" bracket has a threaded hole that the heat sender screws into. I've found it best to have a gap of .010 between the bottom of the sender and the head to avoid a false reading.

The thermostat opens up at about 148 degrees so the engine would run normally around 155 degrees... slightly higher than the thermostat range.