I've got both an 8 degree transducer and a 20 degree transducer for a Lowrance X85 sonar.  I haven't had the 8 degree on the boat for several years.  For bass/walleye fishing over <40' of water with plenty of rock reefs/points and scattered coontail/pondweed beds is there any reason I should re-install the 8 degree transducer?  Does anyone on this board use an 8 degree over a 20 degree... anyone?, anyone?... Bueller?... anyone?

 

oe

'

Generally, if memory serves, the deeper the water, the narrower the cone.  And vice versa, the shallower the water, the wider the cone.

 

Think of it like a flood light and a spot light.  In shallow water, a wider cone, like a flood light, will reveal more of the bottom.  While that may seem like a good thing, in deeper it doesn't give you an accurate picture of the bottom.  The echo is from a much larger area with possibly, conflicting information such as when a bottom transitions from sand to mud or rock, all can be included in the image, in effect, taking it out of "focus".

 

You want to know what's under the boat, not off to the sides.  Side imaging is another matter which gives a lot of info in small slices linked together in the moving display.

 

 

 

 

My thought process 15 years ago when I bought both transducers was to reduce the sonar "hidden zone" tight to steep drop offs and near large boulders.  I was also looking to "see through" the weed canopy a little better with a tighter cone angle which condensed and increased the power slightly.  The science still holds true, I'm not sure it's worth the effort though.

 

oe

8 degree cone angle isn't a consideration for fresh water applications, 20 degree is as narrow as you want. Look at this way 20 degree the cone angle coverage is 1/3 the depth; at 15' depth your coverage is 5' diameter, 30' depth is about 10' diameter. 8 degree is less than 1/2 the coverage or 15' depth is about 2' diameter area at that depth.

Tom

I own one.  I tried it for drop shot but couldn't keep the bait in the cone so I took it off and haven't used it in years.