mercury powerhead

I've heard of the 2004 - early 2005 opti's having a problem with pushing out the powerhead gaskets. Anyone have any info on this? My 04 opti wont hold water pressure so I took it in for water pump. Got called back that the lower powerhead gasket was pushed out letting the pressure get by the exhaust side. Dealer said mercury has since redesigned the gasket. my motor is just a few months out of warranty and mercury wont pay even though it's apparently a known problem. Just looking for info on this "problem".