There is a good manager that will help you with all node versions. It's called
nvm(Node version manager).
All install guides are on git page. I install it like this.
curl -sL https://raw.githubusercontent.com/creationix/nvm/v0.31.0/install.sh -o install_nvm.sh
Check to see if everything installed correctly
Then when you want update node you can just do
nvm install 6.9.1 (or any version you like)
nvm alias default 6.9.1
nvm use default
After restarting of your terminal run
node -v you should have 6.9.1 installed and used.
Hope this helps.