That’s not not true at all! Firstly you must set “custom fields to include in the index” to “all” (settings) and secondly you must copy this script to your functions:
add_filter('relevanssi_excerpt_content', 'excerpt_function', 10, 3);
function excerpt_function($content, $post, $query) {
global $wpdb;
$fields = $wpdb->get_col("SELECT DISTINCT(meta_key) FROM $wpdb->postmeta");
foreach($fields as $key => $field){
$field_value = get_post_meta($post->ID, $field, TRUE);
$content .= ' ' . ( is_array($field_value) ? implode(' ', $field_value) : $field_value );
}
return $content;
}