In functions.php:
function myExcerpt($text) {
$text = str_replace(\']]>\', \']]>\', $text);
$text = strip_tags($text);
$excerpt_length = 50; // max number of words
$words = explode(\' \', $text, $excerpt_length + 1);
array_pop($words);
array_push($words, \'-N\');
$text = implode(\' \', $words);
return $text;
}
In your loops:
echo myExcerpt ( get_the_content() );