788ci HD DI Combo – depth reading bouncing all over

I have a Humminbird 788ci HD DI combo. It worked fine in the back of the boat. Last year I moved it to the front of the boat and hooked it up to the universal transducer on my trolling motor. Everything seems to work correctly, however the bottom depth never seems to lock in. It will read the correct depth and then bounce all over the place, 68′, 29′, 55′, etc. I thought my back unit may be interfering with it but it still does it even when that unit is not on. Is this interference coming from the trolling motor even though I am using the built in universal transducer? Are there settings that can be changed? Anything I can do to fix?

Thanks.

I’ve seen some trolling motors in the water at some really odd angles, but not straight down. I could see that raising heck, if using the sonar in the tm.

When you have your trolling motor in the water, is your shaft vertical within a few degrees?

Other things than can happen is multiple returns, typically on a very hard bottom. It will read multiples. If it is 6′, it might say 12, 18, 24.

FBRM – I think the shaft is vertical or very close. I’ve noticed this while fishing shallow water but, need to confirm it still does it in deeper water also. If I remember correctly from last fall it was doing it in deeper water also. I do remember seeing multiple type returns on the graph, but haven’t thought about whether the numbers that are coming back are multiples or not. I will also check that. Thanks.

Shallow water they really like to throw the incremental return Numbers at you.

I run a 788 on my tm too. FYI

Pretty rare I use it, but it has never been flawless if that is what you might be expecting. It throws interference on my 10&12″ screens the deeper the water the worse. So I tend to only run it on low sensitivity in areas where I might run aground in an attempt to save a prop.

Also, check the duecer to be sure it isn’t scratched to heck. Some people’s trolling motors have seen better days.

FBRM – Thanks for the tips. I may try turning the sensitivity down also.

I have the same issue with my 858. I moved the 858 to the bow after I bought a new Helix. I hooked the 858 to the universal sonar and the depth reading is all over the place. It will read correctly then the next second it is 50′ off. I unhooked the universal sonar and mounted the original transducer for the 858 onto the bottom of the TM. It works fine. But, I don’t like dealing with the transducer cord and wish I could figure out the universal transducer.

Got ahold of MinnKota and will check to see if bad cables are the problem.take the head off your motor and see if the connections are tight coming from the transducer. there’s a cable from the transducer to another cable, to another cable that matches the hummingbird. two many connections could cause problems. Sending me new cables. Update later….

Thanks for the continued feedback!

A 788 DI cannot be hooked up to a universal transducer. This is not supported by Humminbird and the erratic depths you are seeing is caused by using a DI unit which is transmitting to much power to the universal transducer. If you read the FAQ’s for Humminbird this is explained.

I guess that answers the question then! Can the DI be turned off so the unit can still be used? I do not use the DI in front anyway.

Be sure your selected sonar is correct. A “DI” unit can run off a universal transducer just as an “SI” unit can… They just can’t use DI or SI if there isn’t a DI/SI duecer connected.

I forget to mention this earlier but the way to combat double and triple echo is to set your bottom depth manually.

Example if you think you’ll be in less than 10′ then set your bottom depth manually to 11′. It will still double and triple echo, but when it does it’ll be off the screen and unnoticeable and won’t adjust your bottom on chart so it is jumping all over. Try setting manual depth. I need to do that to mine often.

No. A DI unit cannot be used with a universal transducer even if the transducer setting is Dual beam or (83, 200). A DI unit can only be used on a trolling motor with an external transducer which is a DI transducer.

timothy A Winterhalter wrote:

No. A DI unit cannot be used with a universal transducer even if the transducer setting is Dual beam or (83, 200). A DI unit can only be used on a trolling motor with an external transducer which is a DI transducer.

Doesn’t a di unit have 2d capability? I’m very surprised it cannot do as you say. I’ve never owned or even researched a di unit since I never use di anyway so I guess I didn’t know

NOTE: Minn Kota motors with built-in Universal Sonar 2 (including those with i-Pilot Link) are not compatible with Humminbird’s Down Imaging Sonar. An external XTM 9 WIDE DI 20 T (83/200) or XTM 9 DI 25T (200/455) is required for all sonar readings with all HELIX 12 , HELIX 10, HELIX 9, 1100, 900, and 800 Humminbird Down Imaging units. An external XTM 9 DI 25T transducer would be required for the Down Imaging versions of the HELIX 7 and HELIX 5 along with the 788ci HD DI.

Thanks for the great information. Doesn’t seem like it makes a lot of sense to even have the universal sonar as it isn’t compatible with much???

my 798 does this in shallower water, you could also try setting the bottom depth range to your depth instead of using Auto, so if you’re in 8 ft, set the max depth to 10 or 11′; if you’re in 12′ set it to 14 or 15′.

ShldHveBenHreYserdy wrote:

my 798 does this in shallower water, you could also try setting the bottom depth range to your depth instead of using Auto, so if you’re in 8 ft, set the max depth to 10 or 11′; if you’re in 12′ set it to 14 or 15′.

not to be a pain, but why should we have to do this, yesterday I was in 20 fow and my 798 was reading 1500 feet! but my helix 7 next to it reads and shows 20 fow no issues so what is wrong? I guess it could be interference, but if one is right the other should be too