Humminbird 728 not finding GPS puck

I just bought an AS GRP gps puck. When I hook it in to the COM port of my Humminbird 728 fish finder, it doesn't seem to recognize it. The accessory test only shows temperature as connected and GPS as unconnected. I tried the puck on another Humminbird 728 and got the same thing. I reset the unit to defaults as I've read taht sometiems helps but it didn't change anything.

I don't know anybody else around here who has a GPS humminbird unit to test it out either otherwise I wouldn't have to be playing the guessing game trying to figure out what the problem is.

How old is your 728 and which GPS puck did you buy? The older units used the 16 channel puck and many of the new pucks are 50 channel, some of the older units do not have enough power in the unit to run the 50 channel.

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Originally Posted by Bricks

How old is your 728 and which GPS puck did you buy? The older units used the 16 channel puck and many of the new pucks are 50 channel, some of the older units do not have enough power in the unit to run the 50 channel.

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It says that it's capable of using 50 channel GPS on the Humminbird site and it's listed on the compatible list of models on the AS GRP list.

Humminbird :: 728 Fishfinder :: Marine Fishfinder

I have a buddy who has a 997 but he doesn't live close by. I'm gonna try to get it to him and have him try it on his unit and see what happens. He has an AS GR 50 already hooked to his unit and working so he should be able to tell right away if it's the puck or not.

I had a 728 hooked to a 50 channel and dont remember having to do anything different. You may want to make sure you have the newest update of your software.

On my old 778, I think I had to go to "advanced setting" or something like that, then on another menu select NMEA input.

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Originally Posted by Shellback

On my old 778, I think I had to go to "advanced setting" or something like that, then on another menu select NMEA input.

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I found a spot in the settings where I could enable or disable NMEA It was off by default so I turned it on but the puck still didn't show up as connected. The software version is 6.250 which is what Humminbird shows as the newest for this model sonar. I'm going to call Humminbird this week sometime and see what they have to say about it.

I called Humminbird support and after doing some checking, they told me that this puck will work with my 728 AFTER software version 6.3 is released for it. I'm a bit bummed about not being able to use it right now BUT at least I know it's just a matter of updating the software and not a hardware issue. If I can find somebody who has a unit that will support the GRP puck right now but they have the GR50 I will have to see if they will trade me straight up.

If anybody needs to use Humminbird support, don't even bother emailing. The email replies I got back didn't answer my questions at all. I called in and got the answers I was seeking right away and was very pleased with the phone support though.

Call Humminbird back and see if they will swap the GRP out for a GR16 (we don’t sell the GR50 anymore). I doubt that you will notice any operational difference between it and the GR50.