Lake Champlain United - Forums

This winter I picked up a Humminbird 788ci Gps Sonar unit. I installed the unit on my boat and sitting still in the yard the speed was jumping all over the place, from .5mph all the way up to 5.7mph. I contacted Humminbird and they had me send it back to check it out and see what was going on. I shipped it out and had it back on my door step within 5 days. While they had it they did all of the updates and installed a new internal antenna. I then hooked it back up and it still was jumping around. I called them back and was on the phone with them for over an hour and I suggested that they send me an external antenna to try. I figured it was a shot in the dark but what the hell it cant hurt to ask. Without hesitation the CS rep said ok we will get one on the way for you no charge. Needless to say I just put it on the boat and it stays right at 0.0mph while sitting still just like it should. Just a heads up for any other Humminbird owners out there that are having the same problems with the gps speed.

I'm under the impression you should never run a transducer out of water. And I'm 99% sure the manual states this.

Humminbird customer service rocks from what I hear.

So I checked their website and it says the following in bold letters...

Testing your transducer while out of water can damage the transducer, unit, or both.

Yes the transducer can be damaged by operating it out of water. Modern transducers are less likely to be damaged but over time they will be damaged or their quality will be reduced. The transducers are embedde in epoxy and when not in the water they build up heat and the heat destroys the epoxy. The transducer then moves inside the puck and loses its quality and it will eventually fail completly or just become inacurate and somewhat useless.

I am now careful to turn off my sonar units prior to removing the boat from the water and I do not turn my electronics on until after I launch the boat and I am getting ready to get underway. I did a lot of reseach on this subject and recommend you never run your transducer dry.

The speed is checked by GPS

Duckman I know the speed is checked by his GPS; but when you turn on a Humminbird unit with GPS, it also powers the sonar trandsucer unless you unplug the transducer. You can also put most Humminbird units into demo mode which will shut off the power to the tnansducer; but you have to wait until the unit powers up and cycles through before you can change its mode of operation. If you power the unit without a transducer connected, it automatically goes into demo mode.

Funny story..... I forgot my transducer one day ice fishing and decided to drag my Hummingbird out anyway and use the GPS with all my vast array of waypoints to help me find the reef I was looking for. After dragging it and a huge boat battery (I was just winging it) I turned on the unit to find that the GPS doesn't work without the transducer!!! Yup...Fact!!! Not on that unit anyway I always thought the unit had all that built into it, but obviously I was wrong???? Another day of learning in the outdoors I didn't catch a single fish either!!!! LOL