What would you do? re: transducers/depth finder quandary?

[Theresamarie11]

Hi all,
I did several searches but didn't find answers to my questions. If anyone knows of a thread please point me in the right direction.

I have on my 300DA, an ST-60 with through hull transducers for speed/depth/temp, and Furuno Navnet with radar/plotter/fishfinder and P79 in-hull transducer. Then I have a Lowrance HDS unit that I use for plotter today, but have used it on my last boat for it's fishfinder capability (very nice) but left the transducer on the old boat.

The raytheon st 60 depth finder works well at <10mph and 50 feet depth but as soon as we're on plane and/or going 20mph it looses contact and flashes depth. So the raytheon is pretty useless except sitting still or off plane.

The Furuno navnet has a BBFF-1 black box sounder attached and in all honestly, it seems pretty low-quality from an image/resolution standpoint. Not sure if this is normal or a result of a cheap (P79) in hull transducer. Surprisingly, it keeps depth and image to around 30mph and then looses contact. It also seems to loose contact over 150ft at slower speeds. While I don't really need to know exact depths at 150ft for what we do, it takes a long time for it to find bottom again when we go shallow.. so i feel a bit blind (except for plotter depth indications).

I know the HDS can provide excellent, and high speed, depth and imaging but I hate to add a 3rd transducer to the boat if I can get either of the other 2 to work better.

Does anyone have experience with what I have installed, and might there be an issue with one/boths performance such that I could fix them, or are they operating as normal and not really that good and I should just install a transducer on the lowrance HDS unit to get good quality image and high speed depth readings.

Thanks much,
Terri

 

[Henry Boyd]

Terri,

I have the ST-40 depth gauge and it works at all speeds. There is a setting in my setup (I'm assuming the st-60 also) that adjusts the system for vessel speed. You might take a look at that and see if changing fixes your on plane problem.

You might also be shooting yourself in the foot by having two transducers going at once. These things both transmit and receive sonar waves and determine the depth by timing how long it takes. If they are on the same frequency, transducer A might be hearing sonar from transducer B. That would throw off the calculations.

Henry

 

[Theresamarie11]

Terri,

I have the ST-40 depth gauge and it works at all speeds. There is a setting in my setup (I'm assuming the st-60 also) that adjusts the system for vessel speed. You might take a look at that and see if changing fixes your on plane problem.

You might also be shooting yourself in the foot by having two transducers going at once. These things both transmit and receive sonar waves and determine the depth by timing how long it takes. If they are on the same frequency, transducer A might be hearing sonar from transducer B. That would throw off the calculations.

Henry

Henry, thanks for the input, and glad to hear your ST-40 works at all speeds. By chance do you know what transducer you have? Is it a model that came with your boat in 2002. I think mine is a sea ray installation from '02. I will look at the setup but it isn't clear there is any kind of setting for speed on mine, and it does measure speed with a paddle wheel sensor that also measures temp.

A good point on the interference. But I know when going slow, or standstill, the raytheon will measure huge depth (377ft last weekend in Lake Champlain while we ate lunch in the middle of a lake during a pouring rainstorm) while the Furuno seems to top out in the higher 200's while stopped. And while sitting still or going slow, both seem to work fine without interference. But I will alternatively try each one by itself while going at speed.

 

[Henry Boyd]

I added the ST40 and transducer in 2009 when the Lowrance that came with the boat bit the dust. The transducer is just the basic plastic Airmar unit, the Lowrance transducer was on a different frequency. The 'speed' setting I was talking about is an adjustment in the depth gauge to compensate for the speed the boat is moving. One end of the spectrum is for slow moving boats (sail) the other end for high speed (power).

I'd just shut one off and drive the boat with the other going.

Was the depth actually 377 feet, or was the ST 60 acting up? The transducers/gauges do have operating ranges. Mine is 0 to 400 feet. However once the depth gets to about 6 feet the gauge has a hard time. It may be the Furuno is only good to 300 feet.

Henry

Henry

 

[Theresamarie11]

Hi Henry, I've fixed my st-60, which now works quite well at speed. The transducer was one that could be removed (retractable) and in close expection there is an arrow on top which was pointed towards the side of the boat and I just loosened the cap and pointed it fwd... and it now works great! I have no documentation so didn't realize the transducer turned in the mount. The Furuno now works worse once I reglued the base and adjusted it for the exact deadrise as measured. The wild thing is if I turn in either direction, I get a great super strong signal!

 

[Theresamarie11]

Was the depth actually 377 feet, or was the ST 60 acting up? The transducers/gauges do have operating ranges. Mine is 0 to 400 feet. However once the depth gets to about 6 feet the gauge has a hard time. It may be the Furuno is only good to 300 feet.

Henry

Henry

Depth was actually 377'. Champlain is quite deep and we were in one of the deepest areas.