Filter to make the <!--more --> tag do it's thang anywherez.

gistfile1.txt

add_filter('the_excerpt', 'we_aint_got_time_for_more');
function we_aint_got_time_for_more($the_original_excerpt) {
    global $post;
   return explode('<!--more-->', $post->post_content)[0];
}