Also, Base64 is neither encryption nor hashing.
No, it is not a good idea. And here is why: the website name is known to everyone so it is not a secret. Therefore, your base64/base128 encoding (base64/base128 is not a hash) is also not a secret, anyone can base64 the website name and get the identical string of characters that you use as your password. Therefore, your passwords would also not be secrets known only to you.
For a password to be effective, it needs to be known only to you (and obviously known at least once to the site you log into, but they can store a proper hash so they also do not know your actual password either). And it needs to be very hard to guess by an attacker.
Your scheme fails both. What would be your password would be known to anyone who base64 encodes the website name. And because of this it would be trivial to guess by an attacker.
Now, lest you counter argue that an attacker will not know _if_ you are using base64, the reason why that falls is that base64 (and base128) are trivial to compute, so attackers will just add the base64 and base128 encoding of the website name to their password dump cracking tools, and the moment a password dump occurs, your password will be found as fast as they find users that use "password1" as their password.
Just use a password manager (i.e., https://github.com/zdia/gorilla/wiki) where you can generate random, uncorrelated, unique passwords for each site. Then, using the manager, you don't have to remember the individual unique passwords, it performs that function (remembering) for you. All you need to remember then is your master password to unlock the manager.
Once you've begun using a password manager, you'll quickly wonder why you didn't start using it sooner.