I fixed my fishfinder with a garden hose

If the sonar features on your fish finder are malfunctioning, try hosing out the transducer pocket on your kayak.  Sand and other debris in the pocket may be interfering with the sonar signal.

I have a Humminbird fish finder which I like a lot, but during the last couple of weeks its sonar functions started malfunctioning pretty badly. The GPS functions were working well.  At first, periodically the fish finder would switch from registering the actual depth of the water, such as 200 feet, to registering only 1 or 2 feet for a second or so. During those periods a mostly blank strip would appear on the screen, and I couldn't see the bottom of the lake or fish in the water column.  These glitches became more and more frequent, until a few days ago I could only see the full water column for about one out of every ten seconds.  Then it started showing a blank orange screen for extended periods of time. This was not very helpful.

My batteries were about three years old and would sometimes run out of juice in the afternoon.  I had been carrying two battery boxes so I could switch to a different three year old battery if that happened.  I speculated that the fish finder was malfunctioning because my batteries were getting old and weren't providing sufficient power to run the fish finder, so I bought new batteries.  That didn't make any difference at all. 

I decided that the fish finder was pooping out, and started researching new fish finder options.  I know a lot of people who get quite poor performance from their fish finders, and was concerned that if I bought a new fish finder, it wouldn't provide the excellent performance which my current fish finder used to provide.

Then I happened to stick my finger into the transducer pocket on the bottom of my Revolution, and discovered that it contained a lot of sand.  I wondered if the sand was interfering with the sonar signal, so I hosed out the transducer pocket.

Bingo! My fish finder's sonar function is now performing flawlessly, without a single glitch.  So I'm going to start hosing out the transducer pocket after each trip.

If you get a lot of sand in your transducer pocket when doing beach launches, and the sand is interfering with your sonar signal, you could attach a hose to a bilge pump and use it to clean out your transducer pocket when you're on the water.

Fantastic and a good bit of advice for the rest of us.  Nice to know that "old reliable" is still "reliable". 

I always stick the hose down the transducer scupper to blast out any debris hiding in there.

Good call on hosing out the transducer plate after every trip.  Every time I hose mine out there is a fair amount of gunk in there - no matter where I go, salt or fresh.

I've had the same issue you were describing with intermittent signals, but in my case it turned out to be a bad connection to the battery (one of my soldered connections came off a terminal).  That problem was pretty hard to find since the connection was under shrink wrap.  A good reminder to do a better job of pre-heating the terminal and pre-tinning the leads.

Good post! I have had the same problem and solution.