There is a lowrance Bluewater Pro flasher unit mounted in the middle of the dash of my X18 and I'm gonna take it out because I just don't like flashers. But I am wondering if I could mount a depthfinder in there or what I should put in its place, what do you guys think?

The one thing you do not know about flashers is that they provide almost real time information.  The information they provide is much faster than regular LCD locaters.  I asked almost the same question a couple of weeks ago.  By all means keep your flasher. Go here for more info.  http://www.bassresource.com/bass_fishing_forums/YaBB.pl?num=1184248642/3#3

My boat came with an indash flasher and I took it out and put an lcd unit in its place.  I took a plastic cutting board and cut out a pattern that would cover the existing hole and allow the new bracket to be screwed on to it.  It has been working well for over 3 years.  If you are interested I can post a pic or 2.

Keep the flasher, as LM said, its real time. Learn how to read it. Its your best tool for deeper water grass beds, rock piles, sunken islands and such.

If that's one of the old style, dash mount circular flashers, Lowrance now makes a LCD replacement in-dash flasher that sells for around $200.  As Mike said, flashers provide real time readings and are better to use with a thru-hull transducer for depth readings when you're under power.  

My boat came with an indash flasher and I took it out and put an lcd unit in its place.  I took a plastic cutting board and cut out a pattern that would cover the existing hole and allow the new bracket to be screwed on to it.  It has been working well for over 3 years.  If you are interested I can post a pic or 2.

I would really like to see some pics of that, thanks.

However, now hearing what yall have said about flashers I'm thinking about keeping it...not sure yet though.