Changing default excerpt length for search results

Howdy.
When someone searches my blog I want to customize the search result. Default is to use the exceprt or when there is no excerpt, display the first 55 words of the content. I want to be able to customize how many words that are displayed. There does not seem to be any configuration for this, and I cant′t seem to locate where WP sets the 55 word boundary.

Is there a plugin I haven′t found or can someone tell mer where WordPress does the 55 word magic?

TIA, regards
Oskar