I have a Lowrance HDS-5. I noticed a page/screen that has guages on in. My boat did not come with a water pressure guage. Is there a way to link the HDS-5 with my Merc 200 Optimax so I can get water pressure readings from the GPS unit?

Am I better off getting a water pressure guage installed on the dash? (I have room for it)

Can be done, but requires addition of one of the newer Merc Smartcraft units and associated NMEA network components. The least expensive option is to add a WP gauge. However, the Smartcraft will allow you to monitor a LOT more engine info. Check with your Merc dealer. Good luck!

Assuming that your motor has a port for water pressure it's a simple matter to hook it in to your HDS using Lowrance's pressure sensor and the NMEA network.  Lowrance has all the information you need on their web site.  For what it's worth, the "gauges" page on my HDS-8 displays fuel level, voltage, water pressure, fuel consumption in gallons per hour, time, speed, maximum speed per trip and obviously, depth. All it takes is a little time and money.

The age of your motor may have a bearing on whether or not you can do this.  I saw something similar to this on a different forum and they told the guy his opti was too old to work with the hds stuff. 

He was advised to get a smart craft gauge.  I put one of them on my opti.  It was a simple plug and play after I installed it and snaked the wires.

Id suggest Smart Craft gauge, it gives alot of useful information.

cool, thanks guys. The motor is a 2009. I will call my Merc dealer and see what he thinks. Thanks for the suggestions.