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Shoot Through Hull Transducer issue

Old 05-29-2016, 03:54 PM
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Default Shoot Through Hull Transducer issue

I have a Ranger 223 Cayman flats boat with a hockey puck 2d transducer mounted inside the hull under the seat. At speed, I get inaccurate depth readings. Running inshore in 6-8 feet of water at 35 mph my readings vary from 6-8 ft to 18 to 30ft. I replaced the transducer with a new one and still have the problem.

Is it possible that the transducer is too far forward such that that portion of the hull is out of the water when the boat is on plane?
Old 05-29-2016, 06:15 PM
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Is it a true shoot through or a transom mount that is epoxied to the hull? Your suspicion of it being mounted too far forward sounds like the best reason for the inaccuracy. Or a problem w/the installation.
Old 05-29-2016, 06:17 PM
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Your ducer is in the right spot. I think you may just be asking too much of an inhull to work at 35mph. You may have better luck with a transom mount that is in the water more (lower). However, 35 mph is definitely bonus territory for any ducer.
Old 05-29-2016, 10:35 PM
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Need more info.
What is it connected to. Just depth gauge or sounder.?
You say you replaced it, indicating the previous one worked OK and went presumably bad.
How is it mounted?
Old 05-30-2016, 03:25 AM
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It is a true shoot through. I bought the boat used with an old lowrance unit that had a transom mount transducer mounted inside the hull. it had the same problem. the lowrance unit had problems and could not be serviced. I replaced it with a Humminbird Helix 9 SI. I have a hi def SI transducer on the transom and the 2D hockey puck inside the hull. I installed the 2D unit specifically to be able to read at speed.
Old 05-30-2016, 04:16 AM
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You're getting turbulence at that speed. Can be because of many different reasons, but it's turbulence.
Old 05-30-2016, 06:42 AM
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Is this a p79 oil filled or simply a solid transducer glued in hull?
Old 05-30-2016, 04:55 PM
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Is there anything on the hull near the x-ducer. like a strake or something, that could be causing turbulence under the ducer? I had a P79, which is fairly inexpensive, and it gave good bottom picture at all speeds up to WOT of 44 mph on an old Raymarine A65. My new Garmin w/B15 is in the same spot in the boat, and also gives perfect bottom readings at all speeds. It's mounted about 18" off the keel and about 24" forward of the transom. I checked w/the hull mfgr. to be sure I had solid glass in that area.
Old 05-30-2016, 07:06 PM
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It is a solid transducer glued inside the hull. I will check the hull to see if there may be turbulence in that location. I will also call Ranger and see what they have to say. Thanks for the help.
Old 05-30-2016, 08:16 PM
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Originally Posted by Parcall View Post
It is a solid transducer glued inside the hull. I will check the hull to see if there may be turbulence in that location. I will also call Ranger and see what they have to say. Thanks for the help.
Finally..how is it glued, epoxy or silicon type adhesive?
If silicon, redo it with epoxy. But mix it slowly and allow bubbles to escape before mating surfaces. Bubbles and flexible bonding materials absorb ultrasonic energy and distort beam angles by generating side lobes.
I assume the hull is solid fibreglass.
If all is in order, play with the gains on manual control in case the digital lock is seeing second and third reflections.
Old 05-31-2016, 04:33 AM
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Originally Posted by semperfifishing View Post
If you use a P79 I think you would have improved results as it is a true in hull ...and designed to work as such.






.
I don't believe that to be true.
I was installing 'wet box' transducers well over 25 years ago using 4 inch pvc storm water pipe with an end cap. I cut it to match the dead rise and used various Airmar transducers especially the P319 and used vegetable oil as the fluid.
Airmar later released the P79 which in order to fit any deadrise was fabricated with the ability to change angles. Looks impressive.
Guess what? the transducer in the P79 has the same specs as the P319 with a small loss in some, due to propagation through the hull.

Subsequently saying the P79 is designed to work in a wet box is true but a claim made the Airmar marketing boys.
Cost of P79 $299au
Cost of P319 $219au
so housing must cost $80au.
PVC pipe method $8.50au.
Old 05-31-2016, 04:57 AM
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Ok, What you can do is what we have been doing in kayaks for the last ten years. Get a brick of duc seal putty at a hardware store and install the transducer in the putty. This way you can peel it up and move it around to different locations. The duc seal method works amazing. It is better then any glue we ever tried over 30 years and can be quikly peeled up and moved. If there is a deadrise angle in the location you can tilt it in the putty so its plumb. This could be the cause of your problems if you glued it on an angle.
Old 06-02-2016, 10:47 AM
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Default Moving it Back.

Thanks everyone. After speaking with Ranger and with Humminbird, here is what I am going to try first: I am going to move the transducer as far back as possible without going past the drain plug (the drain plug is about 18 inches froward of the stern). Ranger indicates that it may be out of the water at speed. I will let you know.
Old 06-02-2016, 03:03 PM
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Originally Posted by semperfifishing View Post
You might have misunderstood my comment..
If you read the op's post he is using a transom mounted transducer glued to the inner hull hull.

A P79 being a true in hull unit...will indeed give better results vs most glued down transom mounted...as the P79 is designed specially for in hull paramaters.
Simple as that...a P79 or any tank/fluid mount...would be a good choice vs a glued down transom mount.
Just another good option.


In post 5 the OP advised he replaced the glued down one with a "True Shoot Through" and still has the problem. You seem to have missed it. I was referring to the fact there is no such thing as a true shoot through and that the P79 is nothing special, just a standard thru hull fitted in an Airmar housing similar what installers have been fabricating for years.

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