You didn't mention which of our EMS products you have, or the source of your tach signal, but the process is the same.
You need to set the EMS for the number of pulses it will count for 1 RPM. Common values are 1.0, 1.5, and 2.0 Pulses Per Revolution (PPR).
So if you're seeing 50% your expected RPM, decrease the current PPR setting by 50% so it counts half the current number of pulses to display a single RPM - this will increase the displayed RPM by 2x.
In our older EMS products, this is set at:
EMS SETUP > SENSOR > TACHOMETER > PULS/REV R or PULS/REV L.
In SkyView, it's set at:
SETUP MENU > HARDWARE CALIBRATION > EMS CALIBRATION > TACHOMETER CALIBRATION > PUL/REV (C37 P32/P34) or PUL/REV (C37 P33/P35)
If, for example, it's currently set to 1.0, decrease the setting to 0.5 - so for every one (full) pulse it sees, it will display 2 RPM.
Started my 0-320 for the first time on Saturday and the tack only read half of what my digital prop tack read, did I not hook something up right.