Transducer Location

[Wyrguy]

Nice job cob!

I have never heard that which side of the motor you mount your 'ducer is dependent upon theprop direction!
Don't recall reading that in the directions.  Since I am unhappy with the current performance however I am considering relocating it back under the fuel tank like my last one was though.

Sorry cob...not trying to highjack your thread.  Just never heard or read that comment before.

FYI SK, copied from the Airmar installation instructions for transom mounts:

Transom-Mount Mounting Tips
To ensure the best performance, the sensor must be in contact with
aeration-free and turbulence-free water. Mount the sensor on the transom
as close to the center-line (keel) of the boat as possible. On slower heavier
displacement hulls, positioning it farther from the center-line is acceptable.
• Do not mount the transducer near water intake or discharge openings;
or behind strakes, fittings, or hull irregularities.
• Avoid mounting the sensor where the boat may be supported during
trailering, launching, hauling, or storage.
• Single Engine Boat—Mount on the starboard side at least 75 mm (3")
beyond the swing radius of the propeller to avoid propeller turbulence.
• Twin Engine Boat—Mount the sensor between the drives to avoid
propeller turbulence.

Rick

[Salmon King]

Ok rick...thanks.

I cannot recall a time in my life where I have installed a transducer on the starboard side.

Now...I'm wondering how big of a difference it really makes...

Admin...can we move this discussion to a new thread so we don't highjack COB's thread?
I do not want to distract from the great work COB did on his install.

Might I suggest something like 'ducer locations for a title...

Thank you.

[StreamFixer]

Ask and ye shall receive   

My transducer is on the Starboard side and works well.  This boat came with two (two different fish finder systems) transducers, one on each side.  The one I kept happened to be on the Starboard side.  I never thought to move it, it works, so there it stays. 

'Tain't broke, don't fix it'  :biggrin:

StreamFixer

[ak-angler]

Both of my 'ducers sit directly in front of the prop, mounted inside the hull in a shoot-through style. The Garmin is in an oil bath, the Lowrance is bedded in silicone. I know they're not transom mounted, but the Lowrance is within a couple inches of the transom, and the Garmin just a few inches forward of the Lowrance. The only issue with propwash affecting transducer performance in this configuration, is when the motor is in reverse, forcing exhaust under the hull.

I know that the manufacturer's seem to have a preference for mounting their transducers a foot off of centerline on the starboard side. But, for an outboard powered boat, I don't think transducer position relative to the prop is nearly as important as position relative to the hull. For any mounting location to work, the face of the 'ducer needs to be in clean, laminar flow. That's a given. But since the prop on an outboard is typically about 18 inches away, I just don't see how it can create turbulent flow at the transom - especially at speed, where most people complain that they have problems. With a single screw inboard... yeah, you don't want the 'ducer mounted right behind the prop. With an outboard, I just don't think it matters.

[Salmon King]

Had the old Eagle transducer bedded in silicone too...
I didn't do it with the HDS transducer because someone (and I do NOT remember who) told me it would not perform properly.
I think because it had something to do with the dual frequency?...

Anyway...That is the only reason it's mounted on the transom. 
But I placed it on the Port side...and now I don't want to do the hole Drill 'n Fill thing again.

[StreamFixer]

SK

It is working where it is?  As noted earlier, if it ain't broke, don't fix it....

StreamFixer

[Salmon King]

Not as good as the eagle one was when it was siliconed into the bilge.
I tend to lose bottom and get a lot of noise on the screen when I'm on plane.
No problem trolling though.
With the eagle I never lost bottom and there was no noise on the screen ever.
Besides that...I also have not been able to view fish arches either...they only show a partial arch.  More like a slash really.  The leading edge of the return signal.
I have changed the angle with no help and in 1 case it stopped getting returns completely.
I need to talk to an authority (or someone that has done it) concerning using the dual freq. 'Ducer to shoot through the hull.
If that will work then I'll move it to the bilge.

[ak-angler]

Well, I'm not exactly an authority, but I have done it...

I'm currently running two dual frequency transducers, both shooting through the hull on my Sea Ranger. The 83/200 transducer for my Lowrance HDS8 is bedded in silicone, and the 50/200 for my Garmin 178C is in an oil bath. I did pick up some significant static on the HDS8 when I had them both running in dual frequency mode. But, I think I was picking up some cross-talk because both were running on 200hz. Running one of them in single frequency mode (with the 200hz frequency shut off), the static went away and I got great resolution on the Lowrance and kept the solid bottom lock I've come to expect with the Garmin. (It was shocking how much more detail I picked up on the much newer Lowrance unit compared to the older Garmin. The Garmin has always given me solid bottom lock with the oil bath mount, but I had no idea how much detail I was missing in the water column. I may have to play with the settings a bit the next time I'm out.) I don't remember which one I shut off, but now that the boat is sitting on the trailer again, I'll go take a look at how I have them set.

Be right back...

[Salmon King]

Picture me patiently waiting......

[ak-angler]

Well, this isn't going to help. Right now, the Garmin is set on 200hz, and the Lowrance is on 83hz.

But, I am going to try to make it out next weekend to do some early season deer hunting/scouting in the Sound. If the weather cooperates and I do actually get on the water, I'll play with the frequencies and let you know what I find out.

[Salmon King]

That will be a big help actually.

...and I have all winter to complete the project.
Besides...I need to rewire the DR plugs anyway.

I'm looking forward to your report ak...

[ak-angler]

OK... I was finally able to get the boat out this past weekend. While I was out, I was able to play with the FF's a bit. Here's what I found:

No matter what frequency(s) I was running, there was a bit of static on both screens whenever both units were running. There was more when both were using the same frequency, but there was even some with the Garmin set on 200kHz and the Lowrance on 83kHz. I could play with the settings some on the Lowrance and get it pretty clear. But if I tweaked on the Garmin enough to clear the static, I didn't get a good bottom lock with that unit.

Turning the Garmin off cleared the static entirely from the Lowrance, and even allowed me to turn up the sensitivity quite a bit before it started showing any static. The Lowrance didn't seem to have any issues at all with any frequency as long as the Garmin wasn't powered up. And, even with the bit of static present with the Garmin on, the Lowrance gave me good returns from fish that didn't even show up on the Garmin. And, if I cranked the sensitivity up on the Garmin so that I could see those returns, there was quite a bit of static on that unit - but no noticeable increase on the Lowrance.

So, while I may have a bit of a screen clarity issue while running both units at the same time, there doesn't seem to be any problems with either unit by itself in either single or dual frequency modes while shooting through the hull. (And to be honest, the static that I was getting with both units running wasn't too bad.)

[Salmon King]

After fishing this past weekend with a guy that is a sonar expert (he set up my HDS the way it should be).
I can now see fish arches and bait balls and even tell the rough size of the bait in the ball. 
I was able to hold bottom firmly even at 25 mph (faster than I normally go) too.

He advised me to leave the 'ducer right where it is...so I will (at least until I accidentally break the mount off). :nono:

Thanks for all your replies guys...

[Markshoreline]

SK
What changes did your sonar expert make on your set up to create the arches?

[Chief of the Boat]

Mark,
Is your x-ducer set-up like page 22 of this document?  http://www.lowrance.com/Root/Lowrance-Documents/US/HDS_INSTALL_IM_EN_988-10043-001_w.pdf

[Markshoreline]

Good reference- looks like my transducer needs to be lowered, only get partial arcs.  Next time she's out of the water!

[T-Rex]

So you guys are not shooting through any foam correct ?
My tank is out right now, just want to clarify.. other than cutting an additional access hole for transducer mounting & wire routing no additional cutting of the inner liner is needed ? No foam removal ? No Glass work ? what i am looking at under the tank support platform is the inside of the outer hull ?  the bilge pump must also be sitting on the inside of the outer hull with no foam between..
Just Making sure thanks
If this is actually the case then its a cakewalk  :biggrin:

[Threeweight]

There is no foam in the bottom of the hull... you fuel tank should have a flat glass "shelf" under it holding it up.  If it is like mine, there are already a few holes in it for routing hoses and accessing the inside of the drain plug.

Under that should be the curved bottom of the hull.  I would clean it thoroughly, rough it up, clean again with acetone or similar, and mount the transducer there.  You might want to consider mounting it more forward, under the fish box... if something goes wrong, it will be a lot easier to access and service.

All that said, I am not a fan of using a transom mount transducer this way in a fiberglass boat.  Here's the official line on it from Airmar:

From Airmar FAQ:

Question;
Can I mount my transom or thru-hull transducer inside the hull for a shoot-through?

Answer:
We do not recommend it.
Energy is lost passing through thehull; it is like shining a flashlight through a blanket. Transducers designed for a transomor thru-hull mounting do not have sufficient energy to offset this loss. You will not be able to see weak targets. Instead, choose a transducer that is designed for in-hull mounting such as Airmar's P79, M260, R199, or R299.

Link:
http://faq.airmar.com/index.php?action=artikel&cat=1&id=60&artlang=en&highlight=transom+mount+transdcuer+glued+in+the+hull

Airmar FAQ

Question:
Will an in-hull transducer work as well as a transom thru-hull mount?

Answer:
All Airmar in-hull transducers are engineered to offset thesignal-loss from passing through a fiberglass hull. Our in-hull transducers are far more sensitive than mounting a standard transducer inside your hull. And our in-hull models have built-in deadrise correction to aim the transducer's beam straight down toward thebottom. All Airmar in-hull models will perform as well or better than comparable transducers installed outside the hull.

Link:
http://faq.airmar.com/index.php?action=artikel&cat=1&id=53&artlang=en&highlight=transom+mount+transdcuer+glued+in+the+hull

[amazing grace]

If you are talking about using a transom mount transducer as a tru the hull unit, I am with TW. I personally do not like that. Fwiw.

[T-Rex]

Thanks for clearing that up ..
I have no transducer at the moment, i did however remove the old eagle finder and ducer and picked up a Simrad NSS8 & GS25 GPS Antenna, have not decided on which tranducer yet
P79 looks like the ticket  for shoot through but may just grab a P66 and stick with the old school transom mount

[ak-angler]

I don't care what Airmar says. A unit "designed" as a shoot-through may work better than a transom-mount unit in the same application (I'm not actually conceding that point just yet). But, both of my shoot-through installations (using transom-mount style 'ducers) work better than most - and maybe all - of the transom mounted units that I've seen. And, that's good enough for me. :twocents:

[Threeweight]

I had good service out of several transom mounts that I glued inside of kayaks.  That said, I there has to be some loss of clarity with a unit designed for direct immersion in water, that is instead sending and receiving through 1/4" of dense fiberglass.

[ak-angler]

... there has to be some loss of clarity with a unit designed for direct immersion in water, that is instead sending and receiving through 1/4" of dense fiberglass.

Why?

[StreamFixer]

Vibration (signal) dampening both ways (send and receive).  That being said, the sensitivity and selectivity of the transducer, and it's intended purpose (shoot through or immersed) could/will compensate.

The ability of fiberglass to transmit sound waves (which is what a transducer does) is much less than water, but better than air.

StreamFixer

[Threeweight]

What Streamfixer said.

I'm skeptical of product marketing material from any company.  That said, Airmar makes and sells all kinds of transducers, and the price difference between their shoot though the hull and transom mount models is small.  Given that they make some of, if not the, very best transducers on the market for recreational boats, I would be inclined to take their word for it re: which model works best in which application.

That said, I run an Airmar P58 on my transom.