Google has made it easier for Google Site Search users to transfer ownership to different users, after numerous requests to do so. Software engineer Yong Zhu explains on the Google Custom Search blog:
For instance, you may have created, developed and customized your website’s search experience under your Google account, but want the long-term management of the search engine to be performed by someone else. In the past, you would have been required to manually export the configuration, import it into a new Site Search instance and then cancel the old instance.
Now, you can very easily transfer the ownership of a Site Search engine to a new user by simply specifying a different Google account email address in the Business Settings tab in the control panel.
After a user provides their account info for the new admin, a new site search engine is actually created, using the same configuration as the current site search engine. Additionally, the new engine will be officially owned and able to be administered by the new owner.
Google says any unused query quota is transferred to the new site search engine, which will show the transfer history in the business settings in the control panel. Users can still continue to use the old engine, but ads may be displayed alongside search results, and XML access is disabled.
Google also makes a couple of recommendations for new owners after the transfer takes place: review and update admin details in the business settings (license renewal notifications are sent to the email address provided), and edit the search box code on your content pages where Google Site Search is integrated, in order to replace the old search engine ID with the new one.