Excerpt length outside the loop

I am using a loop to display posts from one specific category (10) displaying the post’s thumbnail, it’s title, and an excerpt from it.
I am using the manual excerpt outside of the loop, and it works, except I would like to set a max amount of words so that each post preview looks the same.

I can’t figure out how to set a word limit on the manual excerpt since it’s outside of The Loop.

Thanks for your help!

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