Try THis
Code:
<option value="{$manufacturers_menu[mid].manufacturerid}">{$manufacturers_menu[mid].manufacturer|truncate:17:"...":true}</option>
This will limit the lenght of the name to only 17 characters. you may want to adjust the number accordingly. It allso ads ... at the end of any name it cuts off.
Can you at least get this menu to work I shure can not it will not select the manufacture and display the product if I make a selelction.