Humminbird 788ci HD Di Combo - erratic depth readings

[gerty]

I have just installed a 788ci HD Di Combo. From what I have read on other forums I may have a problem that doesn't have an answer. I wanted to post everything anyway so that hopefully someone can help.

First, I wanted to make sure my transducer was mounted properly. Is it mounted in the right direction? I had found some more info on the Humminbird site that stated the pointed end of the transducer should face the front of the boat, but it just seemed that the way I have it is correct with the bracket and wiring. Here are some pictures:

Does everything look somewhat satisfactory?

I have only had the new unit out twice. The first time it seemed to lose readings at high speeds. I thought, OK, the transducer needs adjustment no big deal. The only thing I have found on that item is that per the way my prop turns (clockwise) it should be mounted on the right side not the left like I have it. I run a 16.5' boat with a 40hp motor. Thoughts.

Second time out I was fishing in very shallow water, 10' to 4'. Many times the depth reading would start reading very high numbers. This was with the big motor back trolling at very slow speeds or with the trolling motor also at very slow speeds. The trolling motor is on the opposite side of the transom from the transducer. So since it did it with the big motor and the trolling motor I think I at least ruled out interference with either. Here is what I have for selections in case it matters:

Advanced mode

Beam select = 200

Image frequency = 455

Switch fire = clear mode

Upper range = 0'

lower range = 13'

Is this something that can be fixed or per what I have been reading this (erratic readings at very shallow depths) is a major flaw with these units??

I would like to know so I can get is returned if need be.

[dairyman]

I would try flipping the transducer as per the manual---------

[mnhunter79]

The surface clutter setting comes preset at 5 i think. set it to 2 or 3. i had the same issue as you,with my 898c si. ths setting fixed the depth reading issue. hope this helps. otherwise google side imaging forum, thats how i found out how to fix the issue

[Chad_Fish]

Your transducer appears to be mounted correctly. I would start by leveling your transducer then installing the latest software update for that unit the 700 series units are known for having problems with erratic shallow water depth readings but the new update should take care of that. As far as high speed readings your probably going to have to install a second high speed transducer.

[mpester]

Do you get a huge rooster tail from the new transducer? I installed a 597ci HD DI unit that has the same transducer and I get a very large rooster tail off the thing. I am wondering if I have it too high or too low in the water.

[gerty]

I have confirmed that the transducer is mounted in the correct direction. I will try adjusting the surface clutter setting, but I think I may have already done that. I will check at lunch to see where it is set. I have all the updates installed so that did not fix any issues.

I think the transducer is pretty level now. Does it look like it needs to be adjusted up or down to you?

I do not have the big rooster tail when I drive. I may have to change the transducer to the other side of the motor to fix the high speed readings, but am more worried about the shallow reading problem at this time. 50% of my fishing is probably under 10'.

[SDS]

The ducer looks a litte lower than it should be. The middle of the ducer should be even with the bottom of the boat. I wouldnt think that a low ducer would give bugus reading, but who knows. My depths also flash when in shallow weeds, hard bottom always reads properly. Other than a lower ducer everything looks good.

[reddog]

Cant see the pictures for some reason, so I cannot comment on the location of the xducer.

Set your Max Depth to 50 or 100, instead of the default 1500, may help also.

[Tator2k]

The rooster-tail is caused by not installing the rubber grommet in the hole between the ducer and mounting bracket. Had the same thing on my new 788c.

[gerty]

Yeah, I have the rubber grommet in mine also. I will try some things, but probably won't be out until this weekend to see if anything works. Thanks for the suggestions.

[TruthWalleyes]

As far as "making sure your ducer is level" try this:

1) Go on lake, boat weighted normally, and drive your normal speed (2-6mph). Put a level on your boat to see how far out of level you are running at those speeds. Use a quarter or several under the level to give you an idea how much out of level you are.

2) Now that you've done that, go home and set your boat to the same level orientation as it is on the water...I.e. if it took 3 quarters to make your bubble center, then adjust your trailer in the parking lot to match.

3) Now, your boat is sitting the same as it does on the water. Put the level on your transducer and set it to level.

4) For high speed problems, do the same at higher speeds. Chances are that your boat will run at different degrees from level at different speeds. So you will have to split the distnace.

Hope that helps for you.

Edit: looking at your pictures above, i would bet that the back of the transducer needs to tip up.