Hp management for key start units:
The key switch must be OFF and the engine stopped to enter setup mode.
Press and hold the SPEED/HOURS/RPM button until the display screen lights up. (display screen is the retangular box located between the temp and fuel gauges)
Press and hold the SPEED/HOURS/RPM button for 3 seconds.
(Each press of the SPEED/HOUR/RPM button while in the setup mode will toggle between the following screens: two-speed, high flow, horsepower management, and tire size.)
The display screen will show [HP 1] for enabled or [HP 0] for disabled. Press the WORK button to toggle between enabled or disabled.
To save selection, press and hold SPEED/HOURS/RPM button until [donE] appears on display screen to save and exit setup.
(To exit without saving, turn the key switch to run or wait 30 seconds without pressing any buttons.)
Hope that helps. Let me know how it works.