m654321,
When you hit the "+" button for a new tab, it will display a page with whatever search engine you currently have set as default to be used in the search box along top of FF and also various recent pages you may have browsed to.
If you want to get rid of Google, just click the upside-down triangle next to Google in the search box and choose "Manage Search Engines".
In Manage Search Engine List, highlight Google and click "Remove" button. You can add other engines to choices available by clicking "Get more search engines...". You can arrange their order with "Move Up" and "Move Down" buttons.
When back on main FF window, just click the upside-down triangle and choose the engine you want to use from list you see. That engine will then be what you see along top of the new tab page when you click the "+" button.