The number of words in a 90 second pitch will depend on the speed at which you speak and the complexity of your message.
On average, a person speaks at a rate of about 150-160 words per minute, so in a 90 second pitch, you might be able to fit around 135-144 words.
However, it is important to keep in mind that your pitch should be focused and to the point, so it may be more effective to use fewer words and emphasize the most important points rather than trying to fit as many words as possible into the allotted time.