Limiting optional excerpt field length

Hi,
I hope that someone can help me or point me in the right direction on this one. It’s a mystery that’s driving me a bit crazy.

My old theme (three years ago) displayed links to older posts as a thumbnail, headline and 25 word excerpt.

It was set up so that, if the optional excerpt field was used, the 25 words came from that (regardless of how much text was entered in the field). If not, then the 25 words came from the body of the post.

The person who set up the theme and site used “the excerpt reloaded” plugin which, from what I can tell, allowed for the 25 word length from the post.

What I can’t figure out is how the length of the optional excerpt field was set to display just the first 25 words. I have about 1200 posts and the optional excerpts are well over the length of what I want to display.

I’ve now changed my theme and my new theme coder and I can’t figure out how it was done.

Any helpful ideas or suggestions would be greatly appreciated.
Thanks.