If you are powering up your own Booyah BombYes, repeatedly sending booyahsrepeated Booyahs will make a Booyah Bomb charge the bombsignificantly faster.
I Booyahed a teammate multiple times in a multiplayer match and saw multiple beams of energy sent their way.
I also tested in the lobby by sending myself Booyahs. The Booyah Bomb took around 6 seconds to charge with a single Booyah as opposed to 2 and a half seconds when I Booyahed ten times by spamming the button.
However, as BunnyMerz pointed out, powering up your own Booyah Bomb may work differently than receiving Booyahs from teammates.