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Transducer location on dory hull.

Old 07-17-2004, 01:46 PM
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Default Transducer location on dory hull.

This is the stern of my 16" Amesbury dory, the transducer is located is just to the inside of the starboard skeg. I put it as close to the skeg and as far away from the prop as I could but at higher speeds I lose the bottom reading. I believe there is some kind of disturbance in the waterflow between the prop and the skeg. Slow speeds and stopped are OK.

Would I get better readings mounting the transducer on the outside of the skeg, out by the edge of the transom?

What about right on the back of the skeg which would bring it lower down?

I'd like to get some advice before turning the transom into a sieve.


Thanks, Rob





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Old 07-17-2004, 04:49 PM
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Default RE: Transducer location on dory hull.

I cant see from the side, but even from the angle of the pic you have I'd say all you need to do is tilt the rear of it down more. The rear has to be tilted below the front by a 1/4" to 3/8".
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Old 07-17-2004, 05:20 PM
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Default RE: Transducer location on dory hull.

Thanks Dad, I'll give it a try.

Rob
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Old 07-17-2004, 08:22 PM
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Default RE: Transducer location on dory hull.

Start with SeaDad's idea first.
If by chance his suggestion doesn't work, I would see if lowering the whole unit a 1/2" would eliminate this problem by placing the transducer's face below the passing stream of water with bubbles and turbulence.
You are very close to the vertical strake and have no dead rise in the bottom, so I think that a high speed, more bubble entraned water is getting sucked in at the bow, and that the strakes and flat hull give it no where to travel except accross the face of the transducer, causing you to loose bottom. You can slot the holes on the mounting bracket, or make a new one, to give the required vertical adjustment, and avoid drilling more holes in the transom. The reason to mout transducer away from the prop is primarily to avoid problems with sending disturbed water, or transducer induced air entrained water to the prop, causing prop cavitation, as the transducer is forward from the prop. The only time I see the propeller causing problems for the transducer is when I send disturbed water at it when moving in reverse.
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Old 07-17-2004, 10:59 PM
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Default RE: Transducer location on dory hull.

On a diffrent subject on your boat. With that flat bottom you can raise that motor till the cavation plate is even with the bottom of the boat.
It will give you some more top end speed.
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Old 07-18-2004, 12:42 AM
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Default RE: Transducer location on dory hull.

The idea that it's the bubbles having no where to go is what prompted my question about moving the transducer outside the skeg. Is that still a viable option?

Thanks for the tip about raising the motor I'll give it a try if I feel I need more speed but that's a Honda 25 and it pushes this flat bottom faster than I care to go right now (g) .


Thanks, Rob
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Old 07-18-2004, 07:26 AM
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Default RE: Transducer location on dory hull.

actually the xducers depth may be too low overall. If you run over a 2x4 it will get cremated. Thats why they have you place the front of the ducers nose so that it's halfway below the hull surface, and half above it. It doesnt take a direct hit that way.

Do not put it on the outside of that skeg. There is nothing but turbulent bubble wwater from there out to the sides of the boat. Its fine right where its at. You can even move it so that its right next to the keel line or anywhere in between if you like as well.

One other point about raising the motor. It will be better on gas from less drag, and you can go in shallower water.
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Old 07-18-2004, 12:07 PM
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Default RE: Transducer location on dory hull.

OK up the motor will go.

The transducer will get tilted nose up and we'll see what happens. BTW the transducer mount is of a "kick up type". If it gets hit it will swivel up.

Thanks, Rob
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Old 07-18-2004, 12:37 PM
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Default RE: Transducer location on dory hull.

Good advice again from Sea Dad on staying inside the skeg and raising the motor.
But if angle doesn't work, then you have nowhere to go but vertically down and back away from the tailing edge of the transom to get the sending and recieving face out of the entrained air and turbulent water's path of travel AT higher speeds.
At slower speeds you get less of the same sucked under the bow, the transom sits a lower in the water when not on plane, and the smaller amount of air/turbulence finds a more vertical path to rise and escape upwards prior to meeting the tranducer.
Hope you can picture this better than I can describe it with my lousy written description.
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Old 07-18-2004, 05:38 PM
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Default RE: Transducer location on dory hull.

Not a bad description at all, I get the picture and thanks to all for the help.

RR
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Old 07-18-2004, 06:56 PM
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Default RE: Transducer location on dory hull.

Let us know how it works out.
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