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Fishfinder advice


sparky
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Hi all,

 

Thinking of replacing fishfinder at next haul out and looking for advice about the

transducer.

Most units come with transom mount in box , but i have thru hull { airmar p19 }

existing which loses bottom return signal at speed.

Wondering whether to change thru hull transducer or use transom mount for new unit.

 

Any advice would be greatly appreciated..

 

Happy new year to everyone.

 

Mick

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Tony,

I have same boat as you with existing thru hull, but go above 12-16 knots and the bottom is lost even in 60foot of water, also you might be in main channel in harbour it will shallow alarm and show 1FOOT........scares the crap out of you!!!!

 

Does anybody have this problem?

 

Mick

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I had transom mount on Little Sal and it was very poor at anything over about 8 knotts. I put an "inhul"l one in and it was amazing difference right up to about 25 knotts. I have a transom mount on Mistress and its rubbish again. I will definately be going the in hull route again before the season.

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I have the same transducer as you and it works fine.

 

Wherever you place the transducer you need clean (no bubbles) water. This means if a through hull keep away from hull strakes through hull fittings and the like. It also means no bubbles in the fibreglass so fix temporarily to see where it works best.

 

Mine (through hull) works well up to the early 20's most of the time not so good if in rough water because of air under the hull. Works right up to 32 knots but not a good picture at that speed but still usable

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The transducer unit is in a part of the hull that is designed to take it, the shape of hull

moulded with a recess for transducer approx 2/3rd from bow and you would think that would be fine,

 

I would say it was underwater at all times , cant go as fast as you and nigel!!!!!!!!!!!!!

 

Perhaps its a faulty transducer, but dont know how to test for this.

 

Mick

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Hello Tony,

 

Have tried .on auto depth setting and manual range.....same on both ?

 

On my MF695 the transducer is on port side just below the step on a flat spot and is

cut through the hull, is yours the same?????

 

Thanks everyone who has replied to this topic for your help.

 

Mick

 

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Hi Mick

 

As a thought could you mount a new (cheap) through hull transducer and then have a switched unit so you can select either transducer.

Just need to make up a switch box or leave the original one in there and connect up the through hull model on a permanent basis haveing once found the best position on the hull.

 

You could just try out a transom version stuck down working through the hull to see if it works ok first. Bluetack or similar is good to find best position on a trial & error basis.

 

Dave

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Edited by Coddy
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Just be aware and ensure we are talking the same language.

 

"Thru" hull as the yanks like to call it means a hole in the hull and the transducer is on the underside of the boat. A true skin fitting.

 

Transom mount is as we all know, the standard transducer that comes with many units, for external mounting on the transom.

 

Here, through hull, tends to mean, a transom mount transducer sending and recieving through the hull material (grp etc). Often mounted on a bed of silicon, plasticine, epoxy or in an oil filled reservoir.

 

Hope that helps,

 

Rob

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My unit is as Rob describes, for "shooting through the hull" rather than "mounting through the hull" in a special tube.

 

It is bedded on epoxy [Glued inside the hull] works fine up to 20 knots and readable above that just like Martins.

 

Best way to test the right spot, or the transducer I know of is;

Take the boat to a bit of deep water, then compare the display from where the transducer is normally mounted to the display after it has been moved to a temporary position when it can be placed directly into the sea.

Not easy to do as any speed, unless it can be temporarly mounted to the transom or attached to a pole.

 

Another method may be to take your unit onto a boat with an identical set, go to sea and compare the boats set display, with yours after swapping the units while the boat is in the same area.

 

Good luck in finding the problem, especially as this weather is far from perfect for sea trials

 

Charlie

 

 

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Hello Tony,

 

Have tried .on auto depth setting and manual range.....same on both ?

 

On my MF695 the transducer is on port side just below the step on a flat spot and is

cut through the hull, is yours the same?????

 

Thanks everyone who has replied to this topic for your help.

 

Mick

Hi Mick

 

My transducer is on the port side to the left of the engine and just behind the water bag

 

I have both a through hull and a shoot thro hull transducer

come and have a look when the weather is better

 

Tony

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Well guys,

 

Plenty of answers to my question, obviously not as simple as expected to find or cure the problem !!!

 

Easiest way seems to be is to get a " shoot thru hull " type as i dont really want to brak seal on old one, any suggestions where i could get one at reasonable cost?

 

Thanks again for all your help gents,

 

Tony, I wouldnt mind seeing your set up when your available.

 

 

Mick

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Now if I was a roofer with nice new van, plenty of wonga and not having to work for it

I Would be happy to spend out..............but as Im only a poor electrician with a 9 year old van ................ANY CHANCE OF A LOAN AT MATES RATES KEV ??????? biggrin.gifbiggrin.gif

 

 

Happy new year to everyone [ including you Kev ]

 

Mick

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