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Message board > Navigation and sea worthiness > Depth Sounder transducer siting

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Message 1 of 5
Posted by member martin smith on Thursday 21 April 2016

I've fitted a Nasa Target 2 Depth Sounder to my River Pilot. I know it works because when I hold it over the side it records the depth accurately.

However the boat appears to be double skinned in most areas and, of course, it won't get a reading. Has anyone fitted one of these to a Pilot, and if so, where did you site the transducer. I'm trying to avoid holes in the bottom of the hull!

Many thanks


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Message 2 of 5
Posted by member Kenny Clark on Friday 22 April 2016

I think best location for transducer may well be trough hull. It's out of the way, less likely to get damaged. More importantly it's gives more accurate reading. Just make allowance for keel depth.

I have located transducer directly below aft battery locker. It can be fitted, adjusted, checked and maintained easily.

Only watch out. If using trailer, make sure rollers do not pass over or land directly on transducer and cause damage.

If looking to avoid through hull install. I suppose there would need to be some sort of bracket or block arrangement on transom with transducer tilted slightly forward, to get reading from underside of hull.

Good luck,


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Message 3 of 5
Posted by member Simon Kidd on Friday 22 April 2016

Hi Martin.

Usually the pilot is single skin under the outboard well (i.e. in the fuel tank well). This is where I've fitted echo sounders to navigators and a River Pilot before. Also - the Nasa transducers usually like to be fitted within an oil bath - they have the info on thier website.

Best Regards


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Message 4 of 5
Posted by member Mike Insall on Monday 25 April 2016

When the "engineer" fitted my first Lowrance fishfinder/depth finder he put the transducer just below the waterline on the stern, BUT, on the wrong side of the prop!
On a clockwise turning prop the transducer should be on the Sb'd side.
The FF went wrong, but even though it was out of guarantee Lowrance replaced it with a new on!
I had been thinking it was pretty daft to have to fit the transducer under the waterline, and had contacted Lowrance to see if they made an extension, but they didn't!
SO, I decided to make my own!
Using a galvanised roof tie from B&Q that was pre-drilled with loads of 6mm holes, I fixed it to the stern about 3/4 of the way up the hull using the bracket that came with the FF.
I fixed the transducer to the bottom end, and fixed a small locking bracket to the bathing step to stop the arm coming up when at speed.
However, I can now lift the arm up when on my drying out berth!
The DF works well even at speed although the FF does not seem to work so well unless I'm going quite slowly! It could however be that there are no fish about!!
My fitting is slightly crude but very effective!
Fitting anything below the waterline unless you have to seems a bad thing to have to do IMHO!
If anyone would like any more details please let me know!
Perhaps I should start producing my own brand of entensions for FF etc!

Mike Insall

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Message 5 of 5
Posted by member mike insall on Saturday 30 April 2016

Update to my last posting!
I was in my local diy store today when a chap noticed my emblazoned sweatshirt, and asked if I was in the marine industry.
It transpired that his company Navico are involved with marine electronics, including Lowrance stuff.
So, I brought up the subject of the problem with fitting transponders below the waterline, and the extension I had made.
He was very interested and said he would look in to the matter, so watch this (Lowrances) space!!


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