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Old 02-04-2009, 08:37 AM   #1
peguinpower
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Kayak Thru Hull Transducer

After hearing so many reports of better fish finder performance by hanging transducers over the side of the kayak, I decided to try it for myself. Try I did but with a more "factory: approach

First of all, some research. Here is what Lowrance has to say about thru the hull installs with purpose built Txs.

"Your unit may read erratic depth with a Shoot-Thru Hull Transducer if the transducer is not intact or if you are using the wrong kind of epoxy. The main reason why you are getting erratic depth with your Shoot-Thru Hull transducer can be traced back to the way the transducer is installed.

Shoot-thru-hull transducers are epoxied directly to the inside of fiberglass boat hulls. The sound is transmitted and received through the hull of the boat - but at the cost of some loss of sonar performance. (You won't be able to "see" as deep with a shoot-thru-hull transducer as one that's mounted on the transom.) The hull has to be made of solid fiberglass. Don't attempt to shoot through aluminum, wood, or steel hulls. Sound can't pass through air (rotomolded kayaks can have air bubbles in the hull), so if there's any wood, metal, or foam reinforcement, it must be removed from the inside of the hull before installing the transducer. Another disadvantage of the shoot-thru-hull transducer is it can't be adjusted for the best fish arches. Although there are disadvantages to a shoot-thru-hull transducer, the advantages are considerable. One, it can't be knocked off by a stump or rock since it's protected inside the hull. Two, since there is nothing protruding into the water flow, it generally works quite well at high speed if it is mounted where a clean laminar flow of water passes over the hull. Three, it can't be fouled by marine growth."

So I pulled out my my old tx. Despite working very well, I guess it was not a perfect installation.




Here is the new unit I'll be putting in.



Onto the installation....

pilot hole



firing up the Ryobi



builder's remorse



hole



clean up. also used acetone. 5200 doesnt like alcohol



test fit



secured with tape before working on the inside



bolting the inside down



before cleaning up the 5200



completion......sea trials on saturday



this project is not for everyone. my kayak is out of warranty. you may or may not have the skills to work stuff like this, find a professional marine installer. you may or may not want a better FF picture, all the best to you. if you are afraid to work below the water line, that's your issue. I always carry a hand action bilge pump. dont be hatin

thanks to our LA County locals for doing it first. Humminbird also helped a lot by providing tech help and advice over the phone.
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Old 02-04-2009, 10:01 AM   #2
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Nice job, where did you get this unit from?



FWIW, I shoot thru Hull on my kayak, and have my puck directly in water on my boat, and haven't noticed a trememdous difference in the reading. I use the same FF/GPS on both kayak and boat, each have their own puck. I wish more kayak manufacturer's would just build an independent puck area on the bottom of the kayak in the mold, and not be a part of the kayaks scupper system.

chris
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Old 02-04-2009, 10:13 AM   #3
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This is a Humminbird Flush Mount Transducer part no. XFM-9-20-P

I got it from Amazon.com

You'll need another part #TG-W to get temps (no hole needed)

The height is 4 to 4.5 inches (approx). The hole is 2 inch round. It it seems to be the standard hole in the FF industry for low power (sub 1000 watt) TXs.

Garmin and Lowrance makes theirs, with Lowrance being the most expensive.
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Old 02-04-2009, 11:00 AM   #4
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penguinpower,

do you get a better picture and depth reading with the new install?

i have an eagle cuda that stops working when i'm at depths greater than 125' and i suspect it's the transducer install that is causing this.

thanks in advance.
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Old 02-04-2009, 11:06 AM   #5
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Solid post-

Did you replace your transducer all together or did it fit inside the unit?

has anyone done this for the eagle cuda series?
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Old 02-04-2009, 11:24 AM   #6
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Quote:
Originally Posted by buki View Post
penguinpower,

do you get a better picture and depth reading with the new install?

i have an eagle cuda that stops working when i'm at depths greater than 125' and i suspect it's the transducer install that is causing this.

thanks in advance.
I'll let you know after this weekend when I do sea trials. my old gooped install saw all the way to 800 feet. the reason I am doing this is the get better pics on the screen. how useful that is, is a personal preference.

I am not the first to do this. Jim Day did his first and a few other guys confirmed that the OK scupper mounted fish finders perform much better than internal installs.

regarding if my tx fit in this tx. its a whole new transducer I had to buy. if you have a new Humminbird FF, send the OG transducer to the company and they will exchange it for free.

again, I do not recommend that anybody else does this. its all up to your skills and if you want a better performing FF.
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Old 02-04-2009, 12:18 PM   #7
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Quote:
Originally Posted by peguinpower View Post
I'll let you know after this weekend when I do sea trials. my old gooped install saw all the way to 800 feet. the reason I am doing this is the get better pics on the screen. how useful that is, is a personal preference.

I am not the first to do this. Jim Day did his first and a few other guys confirmed that the OK scupper mounted fish finders perform much better than internal installs.

regarding if my tx fit in this tx. its a whole new transducer I had to buy. if you have a new Humminbird FF, send the OG transducer to the company and they will exchange it for free.

again, I do not recommend that anybody else does this. its all up to your skills and if you want a better performing FF.
I saw Jim Day's post and it got me interested. After seeing yours, I'm seriously thinking about doing this. Your install is much simpler and looks like something I can do. I already have a kayatank and this isn't a big change for me.

Thanks for the info on the Humminbird. I was going to ask about that. I cracked the LCD on my Eagle Cuda a few weeks ago and I may have to swap it out for a Humminbird.

Thanks.
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Old 02-04-2009, 12:30 PM   #8
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Question

Looking at your install I have a couple of questions.
1. Is that caulk inbetween the transducer and the bottom of the hull?
2. Is that a rubber gascic on the inside? If so wouldn't it be better served on the outside?
Transducer.JPG

I do not mean to come accross as critical to you installation. I have no experiance what so ever. Just wondering. I think that your install is very nice and maybe, one day, I will venture to make a simular modification.

Thanks for your post.

Paul.
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Old 02-04-2009, 12:48 PM   #9
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I have a prowler 13 and a Hummingbird fish finder and I noticed a hugh difference when I mounted the transducer through the scupper hole. Do you think that since your transducer is mounted to the bottom of the kayak that it may get damaged if you drag it across the sand?
Will Hummingbird swap out old transducers for through the hull units?
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Old 02-04-2009, 01:01 PM   #10
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Quote:
Originally Posted by dorf View Post
Looking at your install I have a couple of questions.
1. Is that caulk inbetween the transducer and the bottom of the hull?
2. Is that a rubber gascic on the inside? If so wouldn't it be better served on the outside?
Attachment 975

I do not mean to come accross as critical to you installation. I have no experiance what so ever. Just wondering. I think that your install is very nice and maybe, one day, I will venture to make a simular modification.

Thanks for your post.

Paul.
answers:

1) It is 3M 5200 thru hull sealant - marine and underwater application rated. it is only on the lip of the transducer and on a small canal that is on the threaded body, where it meets the hull. I was unable to take pics of the glue application as I was not sure how much time I had to work with the Fast Cure stuff that I was using. What you see there is what got squeezed out when I turned down the nut.
2) the rubber gasket is on the inside. yes, i initially thought it would be best to put it on the outside, but the manual that came with the transducer recommends specifically a 1/16th bead of marine sealant on the outside lip and a 1/32 bead of the same on the threaded body where it meets the hull. the gasket is pressed on by a hand nut which you bolt bolt down snug, not tight. If you think of it, this set up makes it serviceable. otherwise, the gasket will be ruined by the sealant when removed.

I would be proud to say I thought of this stuff, but actually its all thought out by the manufacturer and they give very specific instructions on how to mount it. Personally, I think they know more than I do about these matters, so I followed it to a T, including very specific instructions on how to handle and use 3M 5200 (no alcohol based solvents for cleaning surfaces and clean up after installation)

/bing

Last edited by peguinpower; 02-04-2009 at 01:25 PM.
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Old 02-04-2009, 01:10 PM   #11
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Quote:
Originally Posted by MVC View Post
I have a prowler 13 and a Hummingbird fish finder and I noticed a hugh difference when I mounted the transducer through the scupper hole. Do you think that since your transducer is mounted to the bottom of the kayak that it may get damaged if you drag it across the sand?
Will Hummingbird swap out old transducers for through the hull units?
answer:

Its a 2 almost 3 year old kayak. I surveyed the bottom and have come to the conclusion that most of the abuse is on the bow and stern tips. The TX is metal ringed plastic. I am not very concerned except when I drag the kayak over a dock's edge. On such occasions, I will be carefull. I hardly do any dock launches anyway.

BTW, when I drag my yak on sand, I lift one end. Most of the time, only the first foot from the stern gets dragged on the sand. I also avoided mouting the TX where I put my cart.

No, Humminbird wouldnt take my old transducer.

/bing
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Old 02-04-2009, 04:24 PM   #12
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Let us know how it works out for you.

-----------------------
For what its worth....
On my last Hobie kayak I used Marine Goop to mount the transducer. It worked ok to find bait, and provided barely acceptable readings up to 200 ft.
You will not know if you have trapped air bubbles until you remove the transducer. I was careful during my installation, but the goop cures too fast and traps air bubbles.

The slow cure epoxy stays fluid and allows any trapped air bubbles to rise to the top and dissipate.

When I removed it at the time of sale I found this:

-----------------------
On my new Hobie kayak I used a slow cure epoxy to mount the transducer. The difference in performance was remarkable. I can follow my iron to the bottom easily. I can also see it clearly with the slightest movement of the rod tip.

I regularly compare to my FF to a friends (Jason), who uses an in hull mount, with the transducer mounted in a foam compartment and immersed in water. Our readings seem the same.

Jason has since mounted his transducer using slow cure epoxy. We'll let you know if there is any difference after its tested out next week.
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Old 02-04-2009, 04:40 PM   #13
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I was aware that epoxy and a real shoot thru hull transducer would work. But considering that Lowrance has a disclaimer that shooting thru the hull would weaken the FF signal and degrade arches, I opted to go whole hog.

Also, if I used a real polyethylene epoxy like poly-welder

http://www.tapplastics.com/shop/product.php?pid=435&

there is no removing the transducer. EVER

/bing
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Old 02-04-2009, 04:55 PM   #14
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My cuda 250 wont read deeper than 350-400ft or so.I have my Trans. sitting in water inside a little open bottom cup siliconed inside the hull.I know I am not dealing with bubbles.I still like the idea of being outside the hull.
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Old 02-14-2009, 01:53 PM   #15
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Just finished the install today. First sunny day in socal in about a week.

FF now has 3 wires coming out. The power, tx and temp sensor.


Temp sensor was zip tied to the sail mast and glue with silicone to the hull bottom. It appears to respond well to ambient temps. The hull should be pretty responsive to ambient water temps. I did a test with a temp gun, there is a 1 degree differential between the FF readout and outside temp of the hull. Adjusted for offset in the FF menu. Spot on now



Last look at the tx, sea trials tomorrow. Gonna bring a pump


Last edited by peguinpower; 02-14-2009 at 02:18 PM.
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Old 02-16-2009, 07:09 AM   #16
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Being that it is still relatively early on the 16th, I hope the sea trial went well. Interrested to hear it any water made it in at all. I had a small pinhole in my old kayak that through the course of the day would suck in gallons of water. Kayaks compress and decompress hundreds of times a day depending on conditions and what not and when they decompress, water gets sucked in......................at least that is what I was told from the manufacturer a couple of years ago. Anyhow that is still one good looking install and hope for the best. I also would like to see more manufacturers make some kind of allowance for transducer mountings and come up with something clever for bringing wiring through the boat * I have one but really do not like the cable clams very much , I do understand that the molds are very expensive and manufacturers are doing their best to think of the needs of the angler. Very good and informational post.
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Old 02-23-2009, 08:42 AM   #17
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Test results:

The original gooped transom mount tx vs. the thru-hull tx, the thru-hull has about 100% better performance. The thru-hull tx versus my other kayak, with a purpose built shoot-thru-hull tx is better by about 30%.

That said, I would say that I may settle for a purpose built shoot-thru-hull installation with epoxy next time. Its a small sacrifice compared to drilling thru the hull Smile

I observed that I get arches on the screen as against having almost none before. I can track a 3/8 oz lead headed swimbait 100% of the time now. Previously, I could only see the heavier metal lures, and even those, intermittently. It was also interesting to see weaker signals, the most interesting of which was seeing an arch over the bottom reading. Halibut? Duhno. Nothing was biting today.

Secondly, the seal. I am not entirely sure if I have a leak. I used the 3M 5200 very sparingly. After 5 hours on the water, I drained the hull and came away with less than 1/4 cup water. On the water, I had a small puddle that you can slap with your hand, but that was all. Nothing a shamwow couldnt handle Smile Not enough to get a hand pump primed.

I am not sure if this was from the transducer or from constantly opening the center hatch to check for leaks. As any Hobie owner knows, opening the center hatch makes water on the hatch drip into the hull.

I will be doing more tests to check if I do have a leak.

Conclusion: I should do a static test in a pool or something, but sadly, I don't have that kind of time right now (the first sea trial lasted 5 hours).

If there is any conclusion to be had at this point, GOOPED transducers are short changing the user. There is more performance to be had with alternative installations.

Do I recommend a thru-the-hull TX installation. If I get a bone dry seal, I would say yes, but that remains to be seen.
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Old 02-23-2009, 09:23 AM   #18
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Bing, looking at the install, I'd be surprised if even one drop came through.
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Old 02-23-2009, 04:18 PM   #19
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I sure wish Lowrance would make one of those
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Old 02-24-2009, 07:23 AM   #20
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Bing, thanks for the motivational post.



FWIW, the hull is almost 1/4" thick where I drilled the hole.

After a solid year of use, this area of the hull has almost no scratches.

Sea trial on Sunday.
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