Force WordPress to NOT display the manual excerpt

You can utilize the wp_trim_excerpt filter. In your callback function that filters the the excerpt text, you can test for the presence of a certain template; then, if that template is being used, you can go ahead and alter the excerpt in any way that you see fit. In order to determine which template is being used, see this clever solution: Get name of the current template file. Let me know if this helps or if you need more.