How can I customize the search results in Bones theme?

Filter 'the_excerpt' on the search page only:

add_filter( 'the_excerpt', 'wpse_99415_search_excerpt' );

function wpse_99415_search_excerpt( $excerpt )
{
    if ( ! is_search() )
        return $excerpt;

    global $post;

    // create a custom excerpt

    return $custom_excerpt;
}