the seal on the raymarine is fine. not sure how it gets moisture inside. the fog would NEVER clear up to where you could see the screen at all till I took it apart and drilled some vent holes in the bottom. now it take a good hour to clear up. been like this for 2 or 3 yrs. almost did a 6,000lb truck test on that sucker. from the day I got it. it has been like that. the factory said nothing wrong with it. won't be buying raymarine again. buddy has 2 of their top of the line units on his boat. he removed on and replaced with a lowrance. he won't be buy raymarine again either. he has other problems that they say aren't there/can't fix.
here's another spot to watch for electronic's.
http://www.jollyannsales.com/
and fishing stuff
http://www.ffo-tackle.com/