I went out today and used the new HDS 5 installed earlier this week.  It worked great and I was impressed with the clarity on the sonar.  Only problem I have is the water temp does not work.  Granted the transducer from the X51 previously installed was not replaced with the new transducer that came with the HDS 5.  Is there a way to turn on or off the water temp or do I need to replace the X51 transducer (it has water temp built in)?  I have looked in the manual but can't locate any information regarding this subject.  I suspect I will need to replace the transcducer but want to make sure I am not missing something before I start tearing into the bow panel

I think you are probably right regarding the transducer. I would recommend giving Lowrance a call. I have found their service folks to be very helpful. You may have to wait a bit before you can get to speak to service...

I have had the HDS 5 for a year, and it has been worth every penny. Good luck.

Check the LEI Extras site. The HDS units transducer is not listed as being compatable with the X51. It is for the X52

Many thanks for the quick response.  I will contact Lowrance.

If I recall correctly, your X51 ducer has a gray connector.  This ducer is compatible with your HDS 5, with the exception of water temp.  Simple fix, just replace the old ducer with the new one.