Tranducer mounting

[Tucker]

Gents,
I want to mount a transom mount Hummingbird transducer on the inside of the hull. I've had pretty good luck on past boats just siliconing the transducer to the hull. Didn't work this time. What does everyone do? I'm just concerned about a depth reading on this unit.

 

[richie rich]

Tuck, can you explain that a bit further? I don't understand how you mount a "transom" mount transducer on the inside of a hull. They are normally mounted on the outside of your transom. Unless you are referring to a thru-hull mount...

 

[ocnslr]

I added a Lowrance transom-mount "skimmer" to the area in the forward bilge. Simply cleaned and prepared the area, then used some thickened epoxy to bond it to the hull. It works just fine, in both 50 and 200 modes.

You can use the old trick of putting the 'ducer in a ziplock bag of water and placing it where you think it will work, then trying it at different speeds to see if the bottom is "clean" of bubbles. You may need someone to hold the transducer in the correct position.

We have no problem tracking at all speeds, and I have held bottom in the Norfolk Canyon at 3,425 ft with both the Lowrance skimmer and the larger Airmar transducer (selector switch between 'ducers and the LBS-1).

Brian

 

[seasick]

Gents,
I want to mount a transom mount Hummingbird transducer on the inside of the hull. I've had pretty good luck on past boats just siliconing the transducer to the hull. Didn't work this time. What does everyone do? I'm just concerned about a depth reading on this unit.

If the hull is not solid glass, let's say it is cored or foamed, the transducer won't work. If the hull is very thick, the signal will be attenuated to a point that the elctronics won't read.
Try the bag of water as mentioned and also more the transducer to different spots.

 

[Strikezone]

Don't you loose some detail when shooting through the hull?

 

[merlin25]

I mounted a Garmin transom transducer as a thru hull with epoxy and it works well. I have a 226 and mounted up against the hull in the forward fuel tank area. I did try the ziplock with water trial and it worked. I also had a little water in the bildge area and just tried setting it in the water and that worked well too.

 

[NIGHTIDES]

Don't you loose some detail when shooting through the hull?

You bet.. Signal strength can be reduced 10-15% on the way out and 10-15% on the way back through the hull.. That is 20-30% loss total.

Something to think about..

 

[Amigo]

Silicone does not cure into a solid HARD mass as expoxy will. The transducer's signal needs the hard epoxy mass to carry the siganl to and through the hull.

I would guess the cured rubbery silicone quivers more than a little bit when the transducer signal passes through it.

 

[catch22]

I used Life Seal to secure a Huminbird transducer, (standard transom mount) in the bilge of a 20' Overnighter. Dead center, just a head of the bilge pumps float switch. This was back in 2000... it still works like a champ. Gives a consistant bottom reading, even at high speed.

Clean the area with a solvent, (I used mineral spirits) and lightly sand, repeat with the solvent. Load up the face of the ducer with sealent, as well as the hull area. Press the ducer into the area and slightly twist the ducer back and forth, (they say that removes any bubbles). Place a board, with a slot for the cable, over the top of the ducer and put some weight on the board, (I used a couple of bricks) and leave it overnight.

One of the advantages to using a soft sealent vs a permanent epoxy is, if you need to replace a failed ducer or you get a new fish finder, it's not too difficult to remove and clean up the area.

 

[jekyl]

Whilst fitting inside the hull definitely works and preserves the integrity of the hull...........It really depends on how you intend to use your sounder.

If you fish in deep water 200+ft and bottom detail is important then the clarity and information you will lose is not acceptable.

Previously,I had a 26 ft boat with an airmar 600w transducer mounted in a wet box with a solid glass hull (it worked well). I then fitted a 600w airmar in a thru hull . I already had a hole from another fitting so it was not hard to do.

I could switch from one to the other by just changing the connection at the rear of the JRC colour sounder. It was easy to see the better contrast, definition and information from the thru hull.

As i didn't have a fairing block the thru hull would lose bottom at cruise speed so then i would switch over to the in hull transducer.

I now have 1kw thru hull with fairing block and get the best of both worlds. I also have a transom mount 600w for redundancy if needed.

So it comes back to how important that underwater info is to you. The top Giant Black Marlin skippers here all use thru hulls, sometimes several, and up to 3 kw with forward facing sonar as well .

At best ,what we see with any sounder is info that needs to be interpreted so the clearer the info the more accurate the interpretation, hopefully.

 

[BobP]

Why would you loose detail?

The hull attenuates it, doesn't change details.

The power output is upped accordingly in auto mode or manual mode by hand.

Unless at very deep depths when power rating doesn't cut it.

Whatever the abiliy of the transdcer is in seeing details should be the same, just need an incremental boost in power to achieve it.

 

[jekyl]

First off I will state that I'm not an electronics engineer.......but i do know what I have seen, and it was quite obvious.

For all of the benefits of keeping the transducer inboard why do fishing professionals choose thru hulls. There are so many factors influencing the image we see on the screen.

Hopefully our friend Ken Lahr will hopefully have something to add to this.

Speaking to him recently was quite an insight into the workings of hydrophonics.

Common sense (often faulty tho') tells me ,adding a 1" minimum, thick barrier, between the transducer and the bottom can't possibly improve definition.

If the in hull signal is enough for your needs then by all means use it as it is less troublesome to install and doesn't compromise the hull integrity.

 

[BobP]

No part of my hull where it is not cored is 1 inch thich, can tell you that.

Transducers are priced from 100 bucks to a grand, aren't they?

That's where the differences are seems to me.

If I place the 1000 buck ducer inside my hull, I expect to perform better than the 100 buck P79 inhull.

But if I place the 1000 buck thru- hull, in hull instead, what the difference in waters less than 200 ft or less than 100 ft ?

That's all I want to know.
Not interested in expert sales office response, if you know what I mean.

For much deeper waters naturally much moe power is needed, so the more expensve ducers have the higher power ratings.

A solid no-void hull and bond is no different than so much water head, my in-hull 100 buck transducer can follow an 8 oz sinker or diamond jig to the bottom, that's good enough fo me - don't see what I'll be getting more of - spending another 900 bucks.

 

[catch22]

I totally agree with what Jekyl is saying. The "shoot thru" method will lose power... there's no way around it.

The Overnighter install, (I mentioned above) was for a basic Huminbird unit. I think the signal return was fine on that unit, but again... it was a lower end model and didn't have a great deal of resolution. The owner was not concerened about the "best possible signal" because he had no plans of using it it very deep water, (under 100').

As far as "upping" the power of the transducer?... I guess it would compensate somewhat for the loss, provided the sonar unit has the power to drive that ducer. And... is that all that's involved with obtaining the best signal quality, (just more power)? I can't help but agree with what Jekyl siad, any interference in between the ducer face and the water, will degrade the "quality" of the signal.

I do know this, (just stayed at a Holliday Inn ).... If your sonar unit puts out 500 watts, the best you can achieve is using a matching 500 watt transducer. If you use a lower power ducer, you risk damaging it. If you use a higher wattage ducer, your just wasting money. I've read somewhere that it's very similar to audio amplifiers and speakers... match the power.

 

[BobP]

Catch, the MFD head automatically ups the power, ducer is not active.

So, in the water depth I fish 00 watts wil lget the job done, twice the depth depth over, even when in-hull mounted.

I can monitor % power in use on my Raymarine, never anywhere near full power. In auto mode I watch it do it's thing changing power and scale, as depth changes greatly naturally on a drift over the rips out here.

Way under full power. If I was out of pwer, yes, I agree, sticking it outside the hull will gain back some power availability.

 

[BobP]

... 600 watts will get the job done ...

 

[jekyl]

Well I have nothing to add, however when i drilled my 265 hull at the keel it was over 1" thick. I'll have to see if I still have the core sample. I was impressed. A friend put a hole in his 38' Riveria to install forward facing furuno sonar and it was well over 4" thick at that point .

I had an article by BIll BIlson, i think ,(legendary Cairns Giant Black Marlin skipper) talking about sounders and transducer placement and how he had an epiphany when a fellow skipper showed him how much more effective a transducer was mounted away from the hull and on the end of a bracket . I seem to recall it was mounted on the outrigger somehow at anchor. He compared that image with his in hull 'ducer and from then on altered his thoughts on the importance of placement and also the importance of different frequencies to acheive different pulse rates depending on the depth you want to "look" at .

 

[Kenlahr]

A lot of "It Depends" feed into this thread. If you take a P66 600w ducer on the trannsom and one shooting through the hull you will see a difference. How much of a difference depends on how and where you fish and what fish you are use to looking at. When you shoot through the hull you are going to loose signal, as stated it could be as high as 30% When you lose power on the transmit you will lose the transducers ability to pickup weaker signals (lower signal to noise ratio). On the return the signal will be weaker also. At that point it depends on the filtering your unit has, if its in auto or manual and how much you know your system. You could filter out additional returns.
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However, Bob makes good points. Simply put, you CAN work around most of this by knowing your system and upping the power going out and increasing the sensitivity as well as turning off auto filters.
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At some point though, you fight a loosing battle. But again, that depends on what your fishing for. Just my 2 cents.

 

[Tucker]

Follow-Up,
Ok I siliconed the ducer to the hull right next to the thru-hull for the live well. I must have screwed something up. The reading jumps all over the place. I get a headache just looking at it. Not sure if it's turbulance or not. We have a lot of seaweed and this may be making it freak-out. It seems to really be all over the place in shallow water.

 

[Strikezone]

Sounds like you're too close to the pick-up for the live well. You might try changing locations and see what you get.