Great question every great software engineer and especially software architect asks at least once.
First of all, you will never going to put 150 blocks in the presentation. Make sure everything is big enough and contains the main parts and logic only, you don't need to describe every block on slides themselves.
I would recommend to watch this awesome video from the David Brown's presentation about the Software Architecture vs Code to see what diagrams he puts on slides and how.
Now some tools:
P.S. may be you could also add a "System Architecture" tag to this question.