Fishfinder problem

I have a Humminbird 170 on my Hobie Outback with the transducer on a sidemount that goes into the water. It normally shows fish on the screen but while I was at Hosmer Lake in Oregon last week it failed to show ANY of those lunker fish you can see under your boat! It is only 5-6 feet deep and clear so you can see them swimming pretty well. I'm wondering if the FF is working at all. I have read most of the posts on setting up the FF and I have it with the sensitivity on 9 and filter on. Any thoughts on this?

Remember in that shallow of water (5-10ft) the "cone" of your transducer beam is not very big at depth. Unless you get a fish inside that small sonar cone you won't see anything.  I'd also dial the sensitivity down a notch or two.

The Humminbird 170 is dual frequency.  The sonar cone angles for 83kHz is 20* and for 200kHz is 60*.   Fish show up on the display either solid fill (83kHz) or hollow fill (200kHz). 

The cone diameter for 60* is 1.155x the depth, and for 20* is 0.353x the depth.  Given a water depth of 5' and a fish depth of 4' the sonar cones at the fish are only 4.6' and 1.4' in diameter.
If you are using FishID+, then the contact needs to meet certain criteria to be marked as a fish.  Those criteria may be difficult to meet with moving fish in very small sonar cones. 

On the other hand, I did have a Humminbird transducer go bad on me, but the failure mode was not as you describe.

Like PP suggests, I'd turn the sensitivity down to 5, turn off the filter, and find deeper water.   When/if you do see fish note whether they are indicated by solid or hollow fill. 

On the other, other hand, if you can see the fish why do you need sonar? 

You guys know your stuff! While we're on topic about FF and shallow water maybe this is a good time for me to ask. I have the transducer for my Lowrance Elite 4 in my outback in the grey puck that came with the install kit. It hold water really well but on my display the first 5 feet of water (when im in 30 feet or more) always shows with a bunch of clutter. It's green on my screen but it resembles a ton of floating debris.
When I'm in 10 feet of water it does the same thing but only for the top 1 foot or so.
Could it be my transducer isn't sitting deep enough in the puck? Or is it normal to have that distorted surface look for the top few feet of water.
Btw, sorry didn't mean to hijack this thread I just thought it was a good place to ask
Paul


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It is called surface clutter, and it is normal.  My guess is that it is caused by sound reflection off the surface and your hull.  Some FF have a surface clutter sensitivity option to help filter it out, but I do not believe the 170 has a specific Surface Clutter filter.  It does have a general noise filter.  I don't worry much about surface clutter. 

It is called surface clutter, and it is normal.  My guess is that it is caused by sound reflection off the surface and your hull.  Some FF have a surface clutter sensitivity option to help filter it out, but I do not believe the 170 has a specific Surface Clutter filter.  It does have a general noise filter.  I don't worry much about surface clutter.

I have the Mark 4 DSI unit and it has the same issues whether shooting through the hull or directly in the water.