# Shoot Thru Hull Transducer



## Nicklaus (Apr 23, 2012)

I have a 27' Ericson and am trying to install a Hawk Eye shoot thru hull transducer.

Has anyone installed this unit, where did they mount it, etc?

I’ve hooked up the display and the transducer works when I hang it overboard, but I can’t find a spot to get a reading through the hull.

Help…


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## ldog68 (Nov 2, 2011)

I heard that using a zip lock bag full of water can be used. By moving it around the hull where you would like to mount it and shooting through the bag of water. Are you going to epoxy it or make a bath for it?


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## paul323 (Mar 13, 2010)

Although I have no direct experience with your boat, I can say that the ziplock bag works well to identify the best positioning. Also look for an area where there won't be too much turbulence in the water. Some boats have problems if it placed too close to the keel.


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## Nicklaus (Apr 23, 2012)

I've tried the ziploc bag and also sticking it in a wad of Vaseline. Neither have worked yet.

I'm wondering if the hull is cored or has a false bottom in the berths.

Anyone know how "flat" does it has to be with the bottom of the Bay? Wondering if I need to get it closer to the centerline for the sonar to bounce properly.


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## Nicklaus (Apr 23, 2012)

ldog68 said:


> I heard that using a zip lock bag full of water can be used. By moving it around the hull where you would like to mount it and shooting through the bag of water. Are you going to epoxy it or make a bath for it?


I'm planning to use a two-part epoxy to adhere it once I find a place that gets a reading.


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## paul323 (Mar 13, 2010)

Hmm...well, my kit is different, but I can see why you are baffled. What you are trying should work! On my 32' I found a good spot amidships, 1/3rd up the hull between the keel, and the waterline. I angled the transducer to point straight down. My model also has a sensitivity adjuster on the display for fine tuning.


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## travlin-easy (Dec 24, 2010)

First and foremost, be sure that you do not have a cored hull. I doubt that it is, but you may wish to check with the manufacturer.

Next, the position of the transducer should be relatively close to the stern, and about halfway between the keep and the waterline. This will provide you with a relatively flat location, which is the best you can hope for. Don't position the transducer close to the keep because part of the signal cone may be blocked.

Be sure you have the correct transducer. A standard, exterior mounted transducer will usually not function when mounted inside the hull--it doesn't provide sufficient sensitivity.

While it is unlikely that there is a false bottom in the Catalina 22, there may be a wooden platform encased within the fiberglass in the area you described. Try locations farther aft and see if this makes a difference. You will have to shoot through a zip-Loc bag filled with water and no air bubbles at all. No transducer can shoot through air--even a small amount.

Hope this helps,

Gary


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## mitiempo (Sep 19, 2008)

The best location on a sailboat is just forward of the keel. In a powerboat aft is where you want it. I have installed quite a few, most with epoxy but a few with silicone. I prefer the epoxy. 

When you are testing it place the transducer in the baggie of water. If the centerline doesn't work try a bit to each side. There shouldn't be a liner in a locker - you can tell usually by the finish - smooth means a liner, roving showing means no liner. I don't think there is any core in the Ericson 27.


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## arf145 (Jul 25, 2007)

Absolute flatness shouldn't be required to get some reading from it--ours is a couple of inches off center. But I would think the more angle you have the less accurate your readings will be relative to the depth right below you. Make sure you aren't right over your keel, eh? Mine is right next to where the thru-hull for the old transducer was.


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## RobGallagher (Aug 22, 2001)

I just picked up a Lowrance 5 chartplotter/fishfinder at a boat show.

I want to install mine forward of the keel but the factory rep at the boat show said to put it aft as there was too much turbulence forward of the keel. It this accurate?

Also, how far forward can the sonar see stuff?

(funny thing is that I haven't even closed on the boat yet..lol)


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## rocinante33 (Dec 4, 2007)

Ericson 27 is a solid fiberglass hull. No core.


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## Gust14882 (Nov 30, 2010)

I installed a standard transom-mount transducer as a shoot-thru by epoxying it to the center of the hull, just forward of the keel. It works great and was much cheaper than the "made as shoot-thru" units Aft there is too much turbulance and to either side of the keel creates dead spots when the boat heels. If you are finding gelcoat on the inner surface, it's probably still part of the liner. The inner surface of the hull is usually a bit rough and will often show texture from the glass fibers beneath the resin.


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## Nicklaus (Apr 23, 2012)

Thanks for everyone's help and advice.

I'll be back out there Saturday with my sandpaper, epoxy, and ziploc bag.

Will keep you posted...


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## tspooner (Jun 18, 2011)

RobGallagher said:


> I just picked up a Lowrance 5 chartplotter/fishfinder at a boat show.
> 
> I want to install mine forward of the keel but the factory rep at the boat show said to put it aft as there was too much turbulence forward of the keel. It this accurate?
> 
> RG - I think I got the same chartplotter/fishfinder at a boatshow. Mine is an Elite-5 by Lowrance but the rep told me to ensure it was mounted forward of the keel where there was LESS turbulence. He also said the keel would impede the sonars forward beam if mounted aft of the keel. The transducer I have is external however I don't see that making much difference.


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## mitiempo (Sep 19, 2008)

Forward, ahead of the keel in a sailboat, aft on a powerboat.


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## FlyNavy (May 14, 2009)

I'll also recommend the forward position. You want to know what the depth is before you hit bottom, not after.
I installed my shoot through hull transducer under the V birth on my San Juan 7.7. Bought a section of PVC clean out pipe with a sufficient I.D. to hold the transducer puck and not much more...3 1/2 inches or maybe 4 inches I believe. Did the water baggie test as a transducer needs a uniform surface to shoot through in order not to send erroneous signals... no cored hulls, no bubbles. Once I found the sweet spot, I siliconed the clean out to the hull, let it dry…very important, filled it with water, did a leak test, dried it out, laid the transducer in, filled the clean out with mineral oil, (doesn't freeze, doesn't bubble, doesn't go rancid) and screwed the clean out cap on leaving a small notch for the transducer wire. Put a dab of silicone on the notch.


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## travlin-easy (Dec 24, 2010)

Flynavy,

Putting the transducer in front of the keel doesn't provide you sufficient time to react to a grounding. By the time you hear the alarm sound you will already be hard aground. Now, depending upon the boat, there could be more turbulence up front than aft. Much of this will depend upon the hull design and weather conditions. In rough seas, there's a lot of bubbles created as the bow crashes into the waves, many of which are dissipated along the sides before reaching the stern. Consequently, it's important to test the transducer sites while underway, preferably in rough sea conditions--times when you need accurate depth information most.

Good Luck,

Gary


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## FlyNavy (May 14, 2009)

So Gary, my comment about knowing what is ahead of me was somewhat tongue in cheek as I'm sure that if you aren't aware of your depth until you run aground it really won't help but.... how is having it behind your keel going to help at all?
Turbulence can certainly be a problem and giving it a test drive in different locations should minimize that.


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## travlin-easy (Dec 24, 2010)

The big difference in having the transducer aft V/S forward is:

1. Less distance to route the wire to the display, which is usually in the cockpit.

2. Most turbulence is produced in the forward section of the boat, thereby providing some distance for the bubbles to dissipate before making it to the transducer location.

3. The hull is usually a bit flatter near the stern, thereby less offset of the signal cone and a more accurate depth reading.

I'm sure there are other reasons, but I just can't think of any at this time. As for the position relative to running aground, it really doesn't make any difference. If you're skimming along at 5 to 7 knots, not paying a bit of attention to your location, and encounter a sharp channel edge, you're more than likely going to run aground, regardless of where the transducer is positioned.

All the best,

Gary


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## kwaltersmi (Aug 14, 2006)

I installed my shoot-thru transducer under the v-berth, in front of my fin keel. It's offset to one side, so I needed the manufacturer provided base plate to be able to mount it level. The display unit (Uniden QT206) also has sensitivity and depth adjustments to account for the distance between the transducer at the bottom of the hull and the surface of the water.

The base provided with my transducer provides a cavity sealed with an o-ring screw-on lid. I filled the base with mineral oil, per the manufacturer instructions. I've had no problems in the 2 years since I've installed it.


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## Diamondjet (Apr 8, 2010)

Hello all.....Same problem here with Norcross Hawkeye 'thru hull' transducer. It works when dipped over the side but fails to provide signal to the display when set in the hull of the Catalina 22 swing keel. I've used silicone, and the baggy filled water with zero results on both.....just '---' on display. The hull does have the roughness associated with laid up fiberglass. Some of the fibers stick 'this way and that' and present a rough surface. Should I sand these down with my palm sander and try again? I have tried the beeswax yet.


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## xymotic (Mar 4, 2005)

FWIW, when I installed a similar Garmin unit in my Pearson I could never get any of the test methods to work, eventually I just gave up and installed it properly, and it worked to 800' and that was with a 1 1/4" thick hull.


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## Nicklaus (Apr 23, 2012)

Diamondjet said:


> Hello all.....Same problem here with Norcross Hawkeye 'thru hull' transducer. It works when dipped over the side but fails to provide signal to the display when set in the hull of the Catalina 22 swing keel. I've used silicone, and the baggy filled water with zero results on both.....just '---' on display. The hull does have the roughness associated with laid up fiberglass. Some of the fibers stick 'this way and that' and present a rough surface. Should I sand these down with my palm sander and try again? I have tried the beeswax yet.


I tried sanding it smooth and it didn't help...


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## Maine Sail (Jan 6, 2003)

travlineasy said:


> Next, the position of the transducer should be relatively close to the stern, and about halfway between the keep and the waterline. This will provide you with a relatively flat location, which is the best you can hope for. Don't position the transducer close to the keep because part of the signal cone may be blocked.


Gary where do you come up with this stuff?

On sailboats Airmar, Raymarine and others recommend forward of the keel. I don't know a boat builder who has ever installed them aft of the keel though I'm sure some did..? Was on three different boats today alone, a C&C 110, Ericson & a Cape Dory all had the ducer in front of the keel ..

There is a nice black and white picture of where to mount it, in the Raymarine depth sounder installation instructions. The only time I see one aft is when a DIY was a previous power boater and they often have keel turbulence issues..

Even Uniden says this; (happened to have the manual in my shop next to me)

*Uniden Depth Sounder Installation:
"On sailboats, mount the transducer where the acoustic beam will
not be shaded by the keel. A spot forward of a fin keel with a
minimum deadrise angle is preferred."*


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## travlin-easy (Dec 24, 2010)

My old Catalina 27 with a fin keel was the second sailboat I fired the transducer through the hull. When I tried positioning the transducer forward of the keel it worked just fine when conditions were calm and the boat wasn't heeled hard. However, when the bay was a bit bumpy and the boat was heeled over the forward turbulence was such that the transducer could not read anything other than the bubbles. I repositioned the transducer to aft of the keel and under the same conditions no problems. I tested my newest Lowrance HD7's transducer at four locations on my Morgan 33, and again, the best results have been closer to the stern--not the bow. So, where do I get this stuff--practical experience.

Now, I've used other manufacturers depth finders in years past, Hummingbird, etc..., but my best readings while shooting through the hull have been when using Lowrance systems.

My best advice is to use whatever works best for YOU! This may take some work and experimentation, but you must keep in mind that every boat's hull is different, the power of the depth finders vary considerably, and the results will, obviously, vary. That's why we use things such as plastic bags, oil-filled reservoirs, etc.. to test the best position for the transducer.

Cheers,

Gary


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## jb1528 (Nov 10, 2010)

I'm late to this discussion but wonder the best way to measure the deadrise angle given the boat rises perpendicular to the centerline and also fore and aft. At least that seams to be the case in my Bristol 32. I have an airmar transducer that was installed by the PO and question its positioning. Do you take the greatest angle and orient the base relative to that? What seems to be the consensus?

thanks
Jim


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