I have a 2017 mercury 25hp efi tiller Elect start power tilt and trim. I called mercury tech support and they told me there is no way to install a tach on my motor other than tiny tach which I have but have my doubts about its accuracy. Looking around at tachs you need a signal wire , ground , and power from ignition switch. Could I run a wire from battery that is switched run a ground and wire to signal ? My ? Is where would I get signal from? Has anyone done this ? Thanks everyone