Lowrance Mark 4 problem

I asked around during the HOW event about a recent problem I'm having with my FF but figured I would put it out here too.  My Lowrance Mark 4 will lose depth every now and again and eventually come back.  Yesterday in American lake I was showing 90 ft of water and then a dark vertical line moved right to left and I was looking at 1.5ft of water.  This issue can last for 5 to 20 min and eventually a white line and back to doing it's job.  Has anyone experienced this issue?  I've looked online and can't find this issue on this model.  I've read everything from power cables to close to the ducer cable to bad head unit/ducer etc.

Thanks!
Adam

Is your transducer gooped or do you put water in the puck?

Gooped

Gooped

Probably an air bubble in the goop. Re-goop or try a water puck.

Gooped

Probably an air bubble in the goop. Re-goop or try a water puck.

+1. Even a small amount of air bubbles can make the thing freak out.
That's why I use a water puck instead of goop. I kept having faulty readings when I had it gooped.

I've heard about air bubble problems but the thing worked great for at least a month before developing a problem (only had my yak since March).  Thanks for the quick responses guys.

If you try to re-goop it, make sure you don't use too much.  I used too much during my first couple of installs and realized that you get a better system with less potential for big air bubbles when you use less.  Just one medium sized bead down the middle of the transducer should be enough. 

Adam,  Why don't you just mount it through a scupper hole.  I have the Mark 4 and mounted the standard transducer as shown in the following pics.  The scupper still drains and the unit works great.

I thought about the scupper mount but worried about something hanging out below my revo.  I'd probably run aground and rip the damn thing off 

Those symptoms are more often than not transducer related.  I'd agree that the first issue to  run down is bubbles in the goop.  But there could be other causes as well.  How are you running your cable from the 'ducer to the head unit?  Does one frequency (83 or 200) work better than the other?

If it was bubbles, I'd expect the lower frequency to work better.  That being said, I recently had an issue in which I accidentally pinched the transducer cable where I ran it through a cable clam.  In this case, the higher frequency worked better.  Had to replace the whole transduce/cable to get it working correctly again.

-Allen