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Old 06-04-2014, 13:50   #1
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Furuno Depth Transducer Choices

Our boat is equipped with a Furuno system (radar, displays, etc) and for depth it has an AIRMAR DST850 smart triducer (includes temperature as well). This unit never has worked that well: it only puts out 100 watts RMS of power and has only half the transducer plate area available as the other half is taken up with the paddle wheel. It sometimes does not reliably find bottom over 100' and has also failed once or twice and needed replacement.

We are looking to improve the transducer situation this haul out. The Furuno dealer has suggested a 600 watt RMS Airmar unit good to 800' but this requires buying an expensive Furuno fishfinder box (DFF1) and is a power hog, requiring that our Furuno chartplotter be run all the time. An advantage of the puny Airmar DST850 unit is that it talks NMEA 2000 and thus draws a minuscule amount of power - 200 ma. With the proposed fishfinder and chartplotter solution running we are looking at consumption of between 4.5 amps and 6.5 amps which is not good for offshore sailing.

Have to choose - like the depth capability of the 600 watt unit but don't want to give up the low power usage of the NMEA unit.

Have any others had to decide this question? Thanks for your thoughts.
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Old 06-04-2014, 16:02   #2
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Re: Furuno Depth Transducer Choices

We have the Airmar DT800 depth/temp transducer (no speed) hooked to our N2K network with a Furuno MFD. Works perfectly to 600' and is powered off the N2K bus using <200mA. They have tilted element versions if you need to mount yours at an angle in the hull.

Mark
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Old 06-04-2014, 16:34   #3
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Re: Furuno Depth Transducer Choices

Thanks Mark. Yes if we don't go ahead with the 600W unit, the 100W DT800 would be our choice.

I think it would work better than the SDT850 even thought the wattage is the same. The DT800 uses the full size element instead of sharing half the available area with the knotmeter paddle wheel. Airmar advertises 80% more depth capability so good to have your confirmation of this.

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Ian
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Old 07-04-2014, 07:43   #4
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Re: Furuno Depth Transducer Choices

I'm curious, since it's a depth-only transducer (not fishfinder), why do you need to see more than 100' ??

How deep is your keel???

Believe me, you'll look at while it's blinking at 600' just as often as 100'.
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Old 07-04-2014, 08:34   #5
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Re: Furuno Depth Transducer Choices

100' would be too shallow for me. I could get by with 300', but like the 600'. While it is not a fishfinder, it is very useful for running ledges and finding seamounts to catch fish over. 100' is pretty much useless for that.

Also, we use it as part of navigation data approaching shoals, islands, etc from off-soundings. 100' is useless there also.

In SW Florida, you only need it to read to 20'!

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Old 07-04-2014, 09:51   #6
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Re: Furuno Depth Transducer Choices

Quote:
Originally Posted by colemj View Post
100' would be too shallow for me. I could get by with 300', but like the 600'. While it is not a fishfinder, it is very useful for running ledges and finding seamounts to catch fish over. 100' is pretty much useless for that.

Also, we use it as part of navigation data approaching shoals, islands, etc from off-soundings. 100' is useless there also.

In SW Florida, you only need it to read to 20'!

Mark


That's kind of my point, if you need more than a depth sounder install a fishfinder.

I have the Airmar D800 in the port hull (600') and the P319 (2000'?) graphing transducer on a DFF1 in the starboard hull.

I did look at the 850 triducer, but since I already had the thruhulls, I don't see the advantage, hence still have the separate units (depth & speed/temp).
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Old 07-04-2014, 11:50   #7
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Re: Furuno Depth Transducer Choices

Just ordered the N2K versions - an Airmar D800 for depth and an ST800 for speed/temp. The power consumption was an issue for us since it takes about 4.5 amps to have have the Furuno DFF1, HUB101 and MDF12 fired up to support the 600w P319 depth transducer. This adds up to 100 amp hours per day. A much lessor concern was finding real estate behind the nav station to mount the DFF1.

I should add to my comment about the DST850 not reliably picking up the bottom. Besides its lower depth range (Airmar advertises 300'), the DST850 triducer did not always reacquire the bottom when coming back into the shallows. You could be in 50' and it would still show off-range. We would need to recycle the N2K instruments to trigger it to pick up correct depth again.

Sailing here on the West Coast of BC, it can go from deep to shallow quite quickly so the more advance warning the better.
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Old 09-11-2014, 21:56   #8
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Re: Furuno Depth Transducer Choices

Hello Ian

Curious how your decision of an Airmar D800 for depth and an ST800 for speed/temp worked out?

Was there a marked improvement in Depth range? I have a similar issue
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Old 10-11-2014, 15:36   #9
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Re: Furuno Depth Transducer Choices

Pelagic,

So far the Airmar D800 for depth has lived up to to its advertising and displays depth to over 400', occasionally to 600'. Much better than the smart triducer model.

The only issue (and had this with the smart triducer as well) is that once off soundings, rather than show a "---", the unit often displays a false depth between 20 - 40'. Possibly the sensitivity increases in deep water and it is picking up an echo from a water density boundary? It is a little unnerving for someone to come on watch as see 26' when the boat is actually in 1,000'+. As soon as the boat gets back into shallower water, the unit usually reverts to an accurate depth although not always and we have had to recycle power to get it to pick up the correct depth. We probably do this when we know we are in <200' and perhaps if we waited longer, it would reset itself and display depth correctly.

Speed unit works fine provided one antifouls the paddle wheel and cleans it after a few weeks of inactivity. Still too early to comment on the reliability of the units but we are glad we made the change even though we had to cut another hole in the boat.

Ian
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Old 11-11-2014, 11:25   #10
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Re: Furuno Depth Transducer Choices

Thanks Ian....I had already purchased the smart triducer to install at next drydock with my new FI instruments and a now much cheaper TZT 14
I will rethink the problem and solutions.....
I don't like the false reading reset problem you still have

Suspect this is a networking problem of processing limitation and I wonder if others have the same irritable problem
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Old 11-11-2014, 13:10   #11
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Re: Furuno Depth Transducer Choices

We have the DT800 for the past 3 years, and when off-soundings it shows random depth numbers along with "---". However, these are not constant depth numbers - they continually jump around, make no sense and are interspersed with lots of "---", so it is very easy to tell they are not real. We don't see it as a problem and assume it is due to the unit picking up returns from previous soundings or a thermocline.

We have never had ours fail to revert to accurate depth when returning on-soundings.

Mark
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