Since the ISync schedule starts every hour and nearly freez the Mac a great working solution is to change the time to something less CPU eating  interval for the shedul process .

Open Terminal window and execute following command string ,change the Second with UNIX time of the schedule you need for your Adressbook <.-> Google contact sync

defaults write ~/Library/LaunchAgents/com.google.GoogleContactSyncAgent StartInterval -int <seconds>

Final with  24h  schedule interval time 

defaults write ~/Library/LaunchAgents/com.google.GoogleContactSyncAgent StartInterval -int 86400

Note for the next re install ,found on the apple forum .Would need a reboot to take effect.

Tools UNIX time Calculator if you need your special timing