Thank you in advanced. I know there are plugins that can do this, but I am looking for a simple solution for my function file. I would like to display the excerpt for all posts with the more tag for public visitors, even for private posts.
I've not tested this, but you should be able to complete this task by placing the following code in your template above the loop.
query_posts( array( 'post_status' => array( 'published', 'private' ) ) );
This should allow for published and private posts to be displayed in that template.