SSL is also a trust factor thing and has been standard and customary for several years now.
Not having an SSL may have not only have a negative impact on your rankings but it will leave a negative impression with site visitors who look for that locked padlock icon to know they are on a site that understands technology -- and that they can trust.
So, SSL really isn't a choice -- it is a necessary part of having a website.
I'd always advise using an ssl, even a basic version. This is NOT essential and your site WILL still rank, however visitors will receive an insecure warning which can be quite off-putting to some viewers. A secure site and secure content will increase your google rank but there are many factors at play. Don't think an ssl will send you to the top of google without a multitude of other methods in place.
My website linksysextendersetupinfo.com does not have an SSL certificate. But now I am planning to have the same. But is in dilemma whether it will boost my rank in google or will disturb my existing ranking in google for time being.
Can anyone help me out in this?
You need to be on SSL. Getting SSL will not cause any ranking disturbance. You'll have more to worry about ranking-wise if you don't go SSL.
Whether you'll get a boost depends on many other factors as well. SSL in of itself is not the end-all-be-all -- just something you need to have to build trust with your site visitors. Which then helps search engines see your site in a more positive light.