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"Shootin" Through"

2397 Views 17 Replies 9 Participants Last post by  Flump
Hi guys,

I bought a Garmin 140ff the other day and installed it in my ply yak.

First transducer install was in a piece of poly pipe that was siliconed to the bottom and transducer was mounted in it. The pipe was filled with water. It worked, but the readings were not strong and the picture on the screen was intermittent.

Next, I smeared silicone to the bottom of the yak and stuck the transducer down on it. There were no air bubbles and the installation was rock solid. This was even worse. The sounder would not read in depths under about 15 feet and often would not read at all.

I thought my power source may have been a little weak so I bought a new 12volt dry cell and charger - no change.

Today in desperation, I took the transducer off the bottom, cleaned it up and drifted about just holding it beside me in the water. Perfect, clear and strong signal. It would seem the unit is working perfectly but it has problems shooting through my ply?

I'm looking for suggestions guys, please help.
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Hi Mick
I got the Garmin ff140 and have found that it shoots fine through my ply hull, although the top 1 metre representation (no matter what the depth) is a bit grey and fuzzy. Other than this I'm picking up clouds of fish as well as clear arches, anchor ropes, branches, etc, but as you know I used 3mm ply. I can even watch me pull up my anchor thats how clear it is!!!!I installed mine in a big blob of Selley's clear bathroom silicone sealant and made sure that there were no air bubbles. Mine doesn't give depths in less than 2.5 metres of water, but still shows the bottom OK to a depth of about 1.5 metres (guess).

You also need to check the gain on the unit. The default setting is AUTO and this is crap as it generally sets the unit to around 60 to 70% so you don't see anything. You need to go into the menu and change it to around 85 to 95%, at this setting everything becomes clear and arches etc start appearing. Also, set the whiteline (bottom lock) to on and set the beam to 14 degrees (I found that 45 degrees presented too much clutter in shallow water).

The depth settings on the menu are also defaulted to AUTO. I've found through trial and error it is best to set this to an absolute value rather than letting the unit trying to work out the depth. It usually takes it a few minutes to figure out it should be on say 10 metre depths rather than 5 metres :x .

I initially found that readings were pretty intermittant but by changing the bottom lock, beam angle, gain and depths through the menu this improved the units operation massively. I've also found that the unit automatically returns to factory settings (i.e. auto everything) if I turn the unit off :evil: . Maybe I got lucky with my placement, I don't know, but if you want any other info on my install I'll go and take some pics, just let me know.
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Hi Mick,
If there is nothing over 5 metres I reckon the unit might struggle through the 4mm ply. I've usually been in water between 3 and 30 metres so the shallow depths aren't too much of a problem.

Setting the whiteline is fairly easy. Press the menu button, then press the down button to get to the setup, then press enter. This takes you into the unit setup. You need to press the down button until you get to the whiteline setting and pressing enter, then either up or down to select on and then enter again.

I've just read the instructions again and the white line determines whether its either a soft or hard bottom (hmmmmm, probably depends on age??? :wink: ) and isn't a bottom lock as such, but I'm sure it helps. It's also set to on as default. Might be worthwhile turning it off and trying it again to see if it makes any difference.
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Just had another thought, but you probably won't want to do this. I was worried about shooting through ply when I installed the ff. I did a bit of research and came to the conclusion that I'd give sticking the transducer in a blob of silicone a try and see if it was OK, and it was.

But, the most common method I saw when this didn't work was to 'thin' out the ply using a chisel or router. Basically this method cut out most of the ply where you wanted the transducer to go and you can build it back up using epoxy (with no bubbles), then stick the transducer down with silicone on this pad. This should give a much better signal.

Also, where are you putting the transducer? Mine is set just behind the back of the seat which guarantees no turbulance. This is important as bubbles may be dragged under the hull if it's too far forward, which will affect the signal.
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Hi Mick,

Looks like you've got your answer. I think that you may be getting air bubbles under the hull from the forward positioning. Before you go chopping the ply, try moving the 'ducer towards the back of the hull with the silicone blob installation. If this doesn't improve things it looks like you've got some careful cutting to do :wink: .

Another alternative I considered :idea: was to cut out a square in the bottom of the hull and glass/epoxy in a small plywood boxed out void so that the 'ducer can sit external to the hull. But then you really need to seal the hole for the wires and it would always be a potential leak point.
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