Depth Finders

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  I've got a Hummingbird Piranha 2. Still have not found any piranha, but it does a good job finding the bottom. It starts at 3 feet, and is subject to thermo boundaries, but it is rugged and dependable. I have mine reading through the motor well because I could not get it to read through the hull. (3/4 inch GRP seems to be too much for it). Others on this list have reported good results just gluing the sensor to the inside of the hull. I paid $80 and it seems worth the money. I like the display.

That is now the the Navman Multi 3100 and includes with all that plus  a countdown function. It retails for 409.95..I can sell it for $350 and include freight Priority Mail. Two weeks We got the next to the cheapest fish finder at Boater's World.  It shows 3 sizes of fish although we don't know the parameters of the sizes.  It has a digital depth reading in feet, meters, or fathoms, deep and shallow alarms, fish alarm and a few other things we haven't tried.  It shows a depiction of the bottom so you tell if it's mud, sand, rock, etc.  It reads to about 400' then goes crazy but comes back as soon as it can again see the bottom.  I think we gave about $110 for it.  Never having had a conventional depth finder, we have nothing to compare it to, but I sure like it.  It is also back lit.

The boat came with an inop. depth finder and the transducer is located on the stern.  Now, someone told me that all depth finders essentially use the same transducer.  As I didn't want to drill yet more holes in the boat, especially at or below the water line while in the water, I spliced the cables.  Works like a champ!  It does come with instructions for mounting either on the stern or to shoot through the hull.  Chris

Chris, it sounds like you got lucky.  Depending on the manufacturer, there   are several different frequency ranges that transducers could emit. Check with the manufacturer to be sure that an existing transducer is compatible with the new display head you want to use with it.  And, the new dual frequency models won't work with a single frequency transducer.