Sonar Washout

[gunflint]

Is it possible that drawing your depth finders power from your starting battery instead of your trolling motor battery could cause your screen to washout when moving at anything but trolling speed? This is the second boat that this depth finder (Lowrance 102c) wouldn't read at anything but slow speed. It's placed on the starboard side of a 40 hp Evinrude.

[marine_man]

When you say "screen washout" do you mean the locator stops working, or you can't see anything on the locator when you're moving?

marine_man

[gunflint]

The screen fills up with color. It looks like the bottom only it's a full screens worth of bottom. The depth will also occasionaly give a false reading. It may read 60 when I'm only in 12 fow.

[ac777]

On our boat the lowrance won't read accurately above about 10 mph. Maybe that's your problem.

[PerchJerker]

Sounds to me like electrical interference.

One thing to try is to keep your 102c power cables away from your motor's power cables and other boat accessories as much as possible. Sometimes even moving them an inch is all you need to clean up the interference. Also, you should be hardwired directly to your battery, not to a fuse buss or anything like that, to make sure you eliminate possible sources of interference. You can test this by running a temporary power connection and leaving it exposed to make sure it works, before tucking the wires away out of sight.

Another thing to try is the sonar setup features in your lowrance. There are settings in there to reduce surface clutter and noise. Try setting this filters at medium or high if needed and see if that does anything to solve the problem.

acc777 - my sonars (all lowrance) work fine at all speeds for me, which on my boat is low 50's. I don't think the problem is your unit, it might be a bad transducer or a bad installation, but it should be something you can correct.

[Down Deep]

I have a Lowrance 510C and had the same thing happen. It worked fine until I throttled up and then washed out. The transducer cable was installed in line with the steering and electrical cable. I tried all the settings to no avail. I moved the transducer cable and the problem was solved. My unit is connected to the starting battery.

[ac777]

Maybe it matters where the transducer is located, ours is only about a foot from the motor, and it could be causing too much prop wash. PerchJerker, wheres your transducer located?

[PerchJerker]

Down Deep - excellent point on the transducer cable.

ac777 - I have 2 transducers that I can use when running with my big motor, one outside the boat (on the transom) between my big motor and my kicker, the other mounted in the bilge where it shoots through the hull. I don't get electrical interference or lose my bottom signal with either transducer. What is the symptom you're having, electrical interference, or losing the bottom signal when moving fast?

[rodmaker]

You have mail (this am)

[ac777]

Losing bottom signal is the problem we have, but we dont have a transducer in the bilge.

[PerchJerker]

I usually don't use my transducer in my bilge, it's there as a backup or if my transom mount loses it's signal, but 99% of the time I use my transom mount one even at WOT.

It's probably cavitation that's causing you to lose your bottom reading. You could try moving your transducer sideways on your hull to get it in "cleaner" water. Or you could try moving it down deeper, so it is below the bottom of the hull. Another trick that will help is tilting the back of the transducer down slighly, so the front comes up slighty - this will result in a more constant and steady flow of water over the face of the transducer and you will have better luck holding your bottom signal. Good luck.

[ac777]

Thanks Perch, I think it will work better with the tilt in the transducer.