How to block porn from search engine

Hey crew,

I turned on the parental control filter for my Nighthawk R7000P and am trying to block all porn. It does a good job, however, I have noticed that you can still do a search in Google or similar search engine and click the "images" tab to view thumbnails of porn that was searched. Yes, you cannot click on the image to bring up the site but you can still see images. Would anyone on here know how I can prevent this in search engines from my router filter either natively or by installing 3rd party software? 

Thank you for your time and consideration