There are many plugins which help you to customize excerpt of posts. Advanced Excerpt is one of them. To use excerpt generated by Advanced Excerpt plugin, please add this code to file functions.php of your active theme:
// CVP - use excerpt generated by Advanced Excerpt plugin
add_filter( 'pt_cv_field_content_final', 'cvp_field_content_final_ade', 10, 2 );
function cvp_field_content_final_ade( $content, $post ) {
$content = get_the_excerpt();
return $content;
}
Best regards,