20 Most Recent Humminbird 798ci SI Combo GPS Receiver Questions & Answers

Do a master reset on the unit. restart and cross your fingers. If this does not resolve the problem you probably have an internal fault with the GPS unit.

I had the same problem. I talked to 3 different technicians on the Humminbird support line about it. All 3 of them confirmed that this is how their technology works. They ping the GPS satellites continuously, and at low speeds the GPS accuracy causes the speed measurement to fluctuate wildly. It smooths right out when you go faster than 3 MPH, since your boat moves far enough at that speed that the GPS accuracy is no longer a problem.Seems like they could easily overcome this issue by averaging GPS readings over a longer time period at low speed (i.e. give the boat enough time to move far enough to eliminate the accuracy issues), but they don't do that.It was a big issue for me since I do a lot of trolling at low speed and need an accurate speed indicator, so I returned the product and bought a Lowrance instead. Lowrance doesn't have this issue.

If you are pertaining to software that is possible. All you have to do is go to www.humminbird.com and create an account which is free. Then have a blank sd card anda card reader attached to your computer. Have you serial and your unit type when creating an account. Then down load the software on to the SD card and when finished slide the sd card in the card slot of the unit. Power the unit on and answer the 2 question it gives you.

You can use the Navionics and also LakeMaster Cards.