I add this on product.tpl. (x-cart 4.1.6)
it is working. I think you don't need to edit product.php
code:
{if $product.manufacturer ne ""}
<table width="100%" cellpadding="0" cellspacing="0">
<tr><td align="left"><a href="manufacturers.php?manufacturerid={$product.m anufacturerid}"><img src="image.php?id={$product.manufacturerid}&type=M " alt="{$manufacturer}" border="0" /></a></td></tr>
</table>
{/if}