Topic: 797 c problems

[shovelhead]

I just put a 797c on my 278 stratos. It is mounted to the jack plate. The problem is the side imaging wont show the bottom till about 8 to 9 mph and is still not a very good image  anything under that it is just a black screen with to white lines. I am new to si just looking for a direction to fix this.

[ITGEEK]

8 to 9 mph is reaching the upper limits of useable side-imaging.
Check your transducer mounting:
Does it have a clear line of sight out both sides?
Is it in an area that is going to get a lot of turbulent water?
Is it too close to your outboard prop?

[shovelhead]

It is clear left to right. I guess i to much water tubulance is the problem it is a good foot from the back of the lower unit.  Should i mount it on the lower step of the hull by live well drain? i have a lowrance transduce down there will it be in the way ?

[Humminbird_Greg]

shovelhead, try posting some images of where the transducer is mounted now and some images of the overall transom area of your boat from different angles.

[shovelhead]

hope this helps

[ITGEEK]

It's hard to tell the attitude of the boat from your pictures, but it looks
to me that your transducer is tilted down too far.
Raise the back of it a little.

[Humminbird_Greg]

shovelhead, could you post some screen snapshots of what you are seeing on the Si sonar of your 797 unit while the boat is drifting, one at about 4 mph and one about 8 to 9 mph (whatever speed that shows you good Si sonar)?

[shovelhead]

i dont have a card in it yet so no screen shots. Here is a pic off my phone and this is at 4 mph and it looks the same at 8 mph. Sorry for the poor pic but all i could get for now.

[Roddy]

I'll go with ITGEEK, the aft end looks to far down and with the way most bass boats set aft down/frount up and the xducer has too much tilt and you have to go 9mph to get a sonar return, tilt the xducer aft end "UP" a lot!!!!

With this Jack Plate installiton the chance of rooster tail, poor hole shot ( prop starvation ) are real high.

Maybe moving the xducer to the 1st hull step and off center by 15" mim would help alot.

Roddy

[Humminbird_Greg]

Does it look the same while drifting (with the motor off) as well?

[shovelhead]

Yes if I put my buddy on the trolling motor with the big motor off it has no effect good or bad. I'm gonna adjust it tonight and try it if that dosent work I will mount it on the step.
 

[Humminbird_Greg]

If you are getting Si sonar data like that with the boat drifting (all motors off) than there is either a problem with the unit or the transducer.  As long as the Si transducer is in the water, with neither Si beam being blocked and no source of interference; than you should be seeing some sort of returns from the bottom besides just the initial bottom returns as your picture is showing.

I would try testing someone else’s Humminbird Si unit (any model) off your transducer and power cable and/or testing your 797c2 unit off of their transducer and power cable (DO NOT have the GPS Receiver connected while testing!).

[shovelhead]

I know its been awhile just hard to work on this thing while its on the lift. I have put my unit on a friends boat and it worked fine so it has to be the transducer location. I would like some tips on where to put it hope these pics help.

[sonar2000]

I would mount it on the lowest part of the keel just left of the water intake. You may have to raise your motor to get a good beam and signal..  Try it with double sided sticky tape first..dont run above a trolling speed or it could come loose while testing..
Chuck

[Humminbird_Greg]

shovelhead,
If your unit worked fine on your friend’s boat than it has to be either the transducer mounting or the transducer itself on your boat.  Even with the transducer at the wrong angle and even if the motor mount were down and blocking one side of the Si sonar; you should still see better Si sonar out of the transducer while drifting than is shown in the image you posted above.  If this is true then I will go back to my original line of thinking that you have a bad transducer and no amount of adjusting it will make up for that.

[whitefish]

shovelhead, I'm struggling with what might be a bad transducer with my 797c2 as well.  I took both the unit and transducer to a Humminbird repair center and both checked out as working fine, but I'm still abit leary.  If moving the transducer around doesn't work, you may want to consider having the transducer tested or bite the bullet and by a new one.  I would try to get your buddies head unit and test it on your boat.  Worth a try.  For my 797, I've confirmed that the head unit is fine as well.

Another problem may be power or interference on your boat.  Is your unit hooked up to the main engine battery or do you run it off a separate battery.  If connected to the main engine, is it a direct connection or wired through the fuse panel?  Is your transducer cable running along power cables?  If so, you may have interference.  Have you inspected your transducer cable for any breaks, cuts or wear?  Look at your buddies setup and compare to your boat.

If your unit worked fine on your friend’s boat than it has to be either the transducer mounting or the transducer itself on your boat.  Even with the transducer at the wrong angle and even if the motor mount were down and blocking one side of the Si sonar; you should still see better Si sonar out of the transducer while drifting than is shown in the image you posted above. 

I played with my SI transducer to try an figure out if I was having setup/angle problems on my boat.  I believe in one of my attempts I did end up with an image like yours.  Also also would regularly loose bottom, so obviously the transducer was setup wrong.