trouble with my sonar

[fiker]

I have an Eagle Fishmark 320.  I installed it last year.
I don't remember having problems with it much at all.  Every sonar I've ever had loses bottom once in a while, but not all the time.

This year, every time I get up on plane, the sonar loses bottom when the depth drops off.  However, when I go across something shallow like 4fow or so, it "catches" bottom again. 

When it seems to lose bottom, the depth just sits there and blinks. 

I've tried moving the transducer up and down a little, but seems to make no difference.

Anybody got any ideas on what to try and "fix" this?

[Slipkey]

When you say "moving it up and down", I assume the transducer is mounted externally and not glassed in? If that is the case, there are a couple of things you might check for:

1)  Are there any scratches or gouges on the bottom of the transducer or on the hull directly in front of where the trandsucer is mounted?  If so, you could have some air bubbles being introduced around the transducer when you increase your speed.  This would weaken the signal and cause the bottom loss except when the water is shallow. 

If this is the case, you should be able to remedy the problem by starting with some 1000 grit sandpaper to smooth things out and then wet sand with 1500 to refinish the surface to a gloss.

2)  Worse, if this happened over the winter there might be an indentation or a hook that set into the hull while the boat was on the trailer.  If this is the case, you'll need to move the transducer to a different location unless you want to flip the boat over to fill and repair the hook.

One last thing to check:  Is your GPS connected directly to your battery terminal or through a fuse block?   If it's connected on the same terminal as the  main engine it could also be electronic noise being introduced by the motor as it increases RPM's.  This wouldn't be noticable at lower RPM's but would cause progressively worse interference as the RPM's increase.   Purchasing some battery terminal blocks should solve this problem.

HTH,

Jon

Update:  The more I think about it, the problem sounds like electrical interference. The first two options would likely cause progressive loss of bottom signal, not an instant loss. - Just a thought

[fiker]

Thanks so much for the tips.

Before I go out and buy the battery blocks, what if I try hooking up the sonar to my trolling motor battery?  That way, it would be on a seperate system?

[canvsbk]

set your ping speed to max - that should handle it

[fiker]

I tried the ping speed on max already, but it didn't work.

[Slipkey]

That depends on your trolling motor setup.  You will get similar electronic interference from your trolling motor (more interference for larger motors/voltages) if you use the fishfinder at the same time as your trolling motor.

This may not be an issue, though if this fishfinder is only used when you are at the helm.   

The nice thing about having your electronics on the cranking battery is that they don't steal power from your trolling motor - which you may need with wind or high current.  They don't draw much in the way of juice,  but your trolling motor will only last as long as the weakest battery. 

One other thing:  For a short-term fix you may try changing the stacking order of the leads (both + & -) connected to the cranking battery.  It could be that this happened over the winter if you disconnected the batteries and then re-connected them with the leads stacked differently on the terminal posts.
It won't be a permanent fix, but it might do the trick for now. 

[OUTLAW]

Don't worry about it we can get it fixed. Go to the basszone.com board there is a gale on the board that will answer all of you questions.

Have a Great day