By default, systemd will use a 1min 30sec timeout when starting and stopping units.
To change this default, all you need to do is edit the system.conf file.

vim /etc/systemd/system.conf  

You'll see several commented out items. Find the following lines:

#DefaultTimeoutStartSec=90s
#DefaultTimeoutStopSec=90s

Uncomment them and change them to whatever you want the new timeouts to be.

DefaultTimeoutStartSec=65s  
DefaultTimeoutStopSec=65s  

You don't want to set these too low. Otherwise, systemd may not have enough time to safely start amd stop units (for example: properly mounting/unmounting filesystems).