Here you have a tutorial about how to change your default search engine. I m not a google fan so I use more Bing!!!
Go to Preferences option. To change the default search engine, click General settings menu available at the top right corner of the browser.
Select Preferences from the available menu list. This would display the following Preferences window.
In the General tab, navigate to Default search engine and select your preferred search engine from the available drop down values. And click the close button available at the top right corner of the Preferences window.
(I recommend Bing)
Now the search engine section in Safari browser should display the changed value as shown below.
Thanks for following,