My buddy has an older moder Lowrance depth finder that sometimes will work some times it won't. The problem is some times it will read 150' when we're sitting in 8' of water. Is there a way to fix this thing or has it gone bad? Don't know much about them and need a place to start. Thanks for any help!!

Start with checking the transponder and making sure it is level (pointing straight down and not at an angle).

I have an old Humminbird that does the same thing but usually only when running full throttle. I just upgraded to a new unit, gonna attempt the install today.

I would start by using the manual setting and reduce the sensitivity/gain. It's probably picking up echoes caused too much gain. Sometimes, espectially in the auto mode, in shallow water they start picking up echoes, this makes them think the water is deeper so they increase the gain more, causing even more echoes, and it keeps thinking the waters is getting deeper and deeper.   This can be a aggrevating when you're in shallow water, the sonar says your in deeper water and the next thing you know the trolling motor is plowing bottom

Start with checking the transponder and making sure it is level (pointing straight down and not at an angle).

I have an old Humminbird that does the same thing but usually only when running full throttle. I just upgraded to a new unit, gonna attempt the install today.

I have a Humminbird DX200 that does the same thing when I'm planed.  I've got an idea of what I'm going to replace it with but I just haven't done it yet.  The transponder is being pushed up by the water and once it is at that angle, it becomes inaccurate.  Sometimes, it won't even register a depth when I'm at full throttle.  

I had the same problem last week on my new boat.  I was in about 10'water and the thing is reading 111'.  When i got home I noticed the transponder and been kicked up and not level.  I then remembered when that probably happened.  I had drifted into some brush while fishing and from then on it started acting up.  Anyway, check the transponder...hope it is that simple for you!

Definitely make sure the transducer is level and tight. But also make sure the plastic housing is smooth and clean, no deposits on it. I polish mine occasionally with sanding cloth until it's black & shiny. Any buildup of film or rough surface can mess up the signals.

Lowering the sensitivity is always best in shallow water, preventing false echos.

Make sure the battery supply AT THE UNIT is at least 12 volts. It will run on less but not efficiently. The transducer requires higher power than the sonar unit.

Listen to the transducer running out of the water. You should hear a steady clicking sound, similar to a small clicking windup clock. If it skips beats it might be burning out. They are like spark plugs, producing just so many pulses.

Jim

Thanks Guys! I think we may have gotten it to work. Put it on manual like was suggested and started getting good readings. Will try it out this weekend and see if it still works. Thanks again!!!!!