Google will be turning its Google Custom Site Search off for this site on July 13, 2017. It has already been disconnected from most of the sites that have used it. The current software will automatically default to Google's free Custom Search Engine product, which sadly comes with unwanted advertisements.
I have had a quick look at a replacement but the costs seem exorbitant so I will just have to see how the Google's free replacement goes. Google Site Search required a block of code to be placed in each web page. I assume other search software providers require the same. As I have about 1000 pages this is a daunting task.
I would be grateful for any comments or suggestions anyone has.