Shoot thru hull placement ideas

[Mahoney]

I am going to be getting into the process of finding a suitable location for a shoot thru the hull application for my transducer.<br /><br />I was wondering if some of you could share some tips and tricks for what to do to initially locate a good location. I.E. How did you hold the transducer in place while testing, and when finally finding a spot, how and what you used to epoxy it to the hull?

 

[amirm]

Re: Shoot thru hull placement ideas

If you have a solid core bottom, then you can put the transducer in a bag with water and lay it on the bottom. Then run the boat and see where it works best. If your bottom is not solid, then this will not work. Ask the builder what your bottom is made out of.<br /><br />Note that no matter what you do, once you put in the transducer, you could cause turbulence that could make it not work. Probably the best advice is to ask the builder and other owners of the same boat where they put it.<br /><br />As for putting it in, you would need to seal the area with 3M 5200 or similar water cured sealant after you drill your hole. Need less to say, the hole should be to be vertical when the boat is moving or you would have another problem of shooting the wrong angle down the bottom. And sealing it may be hard if the hole is drilled at an angle.<br /><br />Also be careful to not to put inline with your props as they could reduce their bite behind them -- again due to turbulence.<br /><br />You may need a fairing fixture to reduce turbulence. Worse case you may have to have a custom one built around the sensor to deal with this.<br /><br />Net, net, thru-hull sensors work best when mounted properly. But they are also more difficult to mount and have higher chance of not working -- at least not at speed.<br /><br />The above comes from experience btw. After getting advice from the builder, I went ahead and paid good money to lift the boat out of water (this was a 32' cat and not trailerable). After putting the transducer in, it never worked at non-idle speeds. Had to get the new smart Raymarine fishfinder with auto-gain just to have reliable depth reading at speed.<br /><br />On my new, smaller boat, I am going with transom mount. Yes, it is lower performance but it is also a lot cheaper to begin with and installation will be very easy.<br /><br />Good luck,<br />Amir

 

[Mahoney]

Re: Shoot thru hull placement ideas

This is a smaller boat that I will be upgrading soon, so I am going to shoot thru hull, no drilled holes. Transom mount was worthles with my configuration, prop churned up a hurricane back there underway at anything above a wake spead.<br /><br />The plastic bag thing is an excelent Idea, that is what I was most interested in. I was debating how to make a dam, and fill the hull up with water, etc.<br /><br />If doing a shoot thru hull(no hole in hull) I know to use a very slow cure epoxy, but have also heard of silicone rubber sealant, among others. what is most recomended?

 

[dingbat]

Re: Shoot thru hull placement ideas

Airmar recommends Lifeseal by Boatlife.

 

[Mahoney]

Re: Shoot thru hull placement ideas

It says that stuff is fast curing. Everything I have read indicates using something that is very slow curing to allow any air bubble so dissipate.<br /><br />Has anyone had a problem with this? I would assume you would be able to see the airbubbles if you werent careful in the application, and could just "try again"

 

[ufm82]

Re: Shoot thru hull placement ideas

amir- you are referring to a true "thru-hull" transducer. They are the best but they require a lot of work. A "shoot thru" is very easy to install and is a very clean way to go. <br /><br /> Mahoney, the 'ducer in a bag works very well, but if the bilge has water in it anyway, I have found that you can simply lay the transducer in the water and hold it in place with a heavy shot bag or bean bag. You can move it around in the bilge as you drive but normally the center of the boat is smooth and turbulence-free. Mine is dead center and reads perfectly. I used a 2 part slow curing epoxy not because of air bubbles but to allow me to reposition if needed. Turns out I got it right the first time and was very pleased with the results. Using a paper towel or toilet paper tube, (depending on the size of your 'ducer) form a disc of epoxy on the area where you plan to place the 'ducer. Then, slowly push the 'ducer into the epoxy using a slow back and forth twisting motion to make sure the 'ducer is completely coated with the epoxy. Press it tight against the hull and weight it overnight while the epoxy cures. <br /><br /> The added benefit to this method is that if you ever need to remove the 'ducer for some reason, a sharp rap with a hammer can normally pop the epoxy disc off the hull and free the 'ducer. <br /><br /> I really think that if more people knew how easy it is to install a shoot thru, you wouldn't see very many transom mount 'ducers anymore. They are just a pain. <br /><br />UFM82

 

[Mahoney]

Re: Shoot thru hull placement ideas

This is excactly what I was looking for. Thanks all, now if it would just quit raining.....

 

[reka12]

Re: Shoot thru hull placement ideas

I just put in a shoot through on my little 14.5. Found a spot out of the way underneath a bench. The roven woven, which is the upper part of the hull, at this location was rough and not faired so I used straighup West Epoxy with slow hardener. Once a smooth surface was obtained, I used the same mix to mount the transducer. I used one of Realgun's rocks to hold it in place until cure. I have a real nice readings and it works great. <br /><br />As for location, near a spot where the hull is the flattest and near the rear. If it is too far forward, it may not read well (or at all) while on the plane. You definately need to epoxy it to a spot where you have only glass or a solid core. Mike

 

[inthesticksnow]

Re: Shoot thru hull placement ideas

What’s up with the water bit? My bilge is normally pretty dry, especially amidships where I planned to epoxy. I did not realize that locating a spot for a shoot-through-the-hull transducer required it to be submerged in water. What’s up with this?

 

[dingbat]

Re: Shoot thru hull placement ideas

The one thing not addressed is the accuracy of the reading. Sitting the transducer in a bag of water and running around to see if you have "noise" is one thing, but that does not address the accuracy issue.<br />The hull will absorb some of the signal and will affect the accuracy so you need a base line depth to compare your thru-hull readings against. Compare the baseline against your thru-hull readings to find the best location for your transducer. <br /><br />Baseline measurements should be taken in deep of water as close to the limits of your machine as possible. In my case I have a second unit on board so it was easy to compare the readings between the two machines. If you don't have that luxury you can easily determine a base line by just holding the transducer over the side and observe the readings<br /><br />I took my baseline reading in 85’of water and saw almost a 5 foot variance depending on where I located the transducer in the bilge. I got the worst readings right dead on the center line of the hull and the best readings offset about 12inches from the center. When all was said and done I ended up with accuracy of under a foot when compare with the other unit.

 

[Mahoney]

Re: Shoot thru hull placement ideas

good point. this has a 500RMS transducer factory rated to 1500 feet, so I was hoping a little signal loss is going to be fine with this settup. I do have a 100 ft lake down the street I will do the comparisons with.

 

[ufm82]

Re: Shoot thru hull placement ideas

Inthesticks,<br /> The transducer doesn't have to be under water itself- but it does have to have a way for the signal to be transmitted. If you simply laid the transducer in the bilge and it was dry, it wouldn't give you any reading because there would be no medium for the signal to travel. It won't go through to the hull without the water for the "connection" so to speak. <br /><br /> Once the transducer is epoxied in place, it essentially becomes one piece with the hull. The signal is transmitted through the plastic transducer housing, the epoxy and the fiberglass hull as if it was all one piece. If the transducer just lays there, there's no connection. <br /><br /> If you plan to mount the transducer amidship, make absolutely certain that that the section of hull stays wet. That means don't mount it where the hull may come out of the water such as when you're on plane. You have to have contact with the water on the hull for the thing to work. <br /><br />UFM82

 

[inthesticksnow]

Re: Shoot thru hull placement ideas

UFM,<br /><br />Thanks for answering my question and for your explanation! This is what I needed to know. I am leaning now on mounting somewhere in the engine bilge area, as my '05 Bayliner 185 stands up high on plane pretty high. I recently learned that earlier 185's had factory installed shoot-through transducers installed in the engine compartment part of the bilge. <br /><br />From the pictures I've seen of a '98, it looks like there was a designated placement for the 'ducer just a few inches to starboard of the front engine mount... a hockey-puck sized 'ducer, glued atop a formed mound which looks like a hull design specifically for that installation. <br /><br />As soon as I can, I am going to the boat to see if such “mound” exists in my ’05 hull. If not, I am going to contact my dealer, or Bayliner, to get recommendations for the best placement for my transducer. <br /><br />I can’t see myself at this point placing a loose transducer in a bag of water all over different positions.<br /><br />As to calibration… once I find the proper location for the ‘ducer, epoxy it, etc., I am going to anchor somewhere close to shore, and do an actual sounding with marked line for final adjustments to the gage.<br /><br />Thanks again!