Garmin Fishfinders

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From: Mike (Original Message) Sent: 9/11/2003 11:08 PM
Is anyone using a Garmin fishfinder with any degree of success? A while back I bought the GSD 20 Sounder Module and a fancy transducer (for the tune of about five hundred bucks) to go with my Garmin 2006C GPS unit. I must say, I am very disappointed.

The only time I see those arches they tout are when the thing is in simulator mode. In real time, I haven't seen one yet. To get any clear indication of fish under the boat, I have to turn on the dorky fish symbols, and I hate 'em. I have messed with the gain and noise reject and every other thing I can find to screw with, but to no avail.

Do the fish really show up as "arches", or is that just a sales gimmick to keep you from buying Lowrance? There is no way my wife will let me buy a real fishfinder now.

From: Mike Sent: 9/11/2003 11:17 PM
I also am having a bit of trouble keeping a lock on the bottom when above 15 knots or so. I mounted the transducer halfway between the motor and the trim tab. I whittled the shim they provide to get it nearly parallel to the bottom of the hull, and it is ever so slightly tipped down at the back and about 1/16" below the botoom of the boat.

The other day, when someone else was driving at cruise speed, I looked down at the thing in the water and saw a whole bunch of turbulence coming mostly fom the trim tab. The water was really swirling around the transducer. I think I will try lowering it a little deeper into the water, maybe a quarter inch or so, and see if that makes a difference. The turbulence that the transducer kicks up can't be as bad as what is there now.

The unit has the water speed wheel at the back and is a pretty good size piece of plastic. It is too big to mount in the trim tab like Greg did, or I would try that for sure. I am using the Bennett Sport Tabs, and they have the 90º lip at the sides. That may be adding the the amount they disturb the water.

I could try moving the transducer closer to the motor, because in look calmer there. Now I wish I had gone ahead and used the mounting board instead of screwing the bracket right to the hull. Maybe this winter I can patch the holes and go to a mounting board. I kind of have this plan for one that will allow adjustment both side-to-side and vertically.

Any suggestions?

From: Redƒox Sent: 9/12/2003 8:07 PM
Well the fish don't show up on my sounder as arches, they show up as lines or spots mostly (the larger fish) or as big dark patches (the "feed" fish in large schools)

Hey, I trimmed off that speed wheel mounting on my t'ducer, to get a smaller hole for it to fit into. I recomend making a mounting out of plastic that will acomodate your trimmed down t'ducer right off the trim tab. I think it gets a cleaner signal that way because it's farther away from the flat hull that traps more noise.... (I recon anyway)

From: Rooster27509 Sent: 9/14/2003 12:15 PM

This is what I found on your question about the "arch" of not getting one.

I have the same set up as you and other than having Garmin sending me the update program it's been great. When it works it stopped and per a phone call they said I needed the new program and it will be here this week.

Q. I have a fish symbols turned off on my Fishfinder/Sounder. Why don't I get any arches?
A. When the Fish ID is turned off, you will see an actual representation of the sonar echo. The sonar pulse is a convex wave that goes out of the transducer. The only way the unit will show a perfect arch or half moon is if the fish enters the front of the cone, goes straight toward the center and out the back. This would cause the echo to get closer toward the center, causing the arch. If a fish enters the cone and goes out the side, you may get a partial arch or just a black spot on the screen. When using the unit with the Fish ID off, set the gain to around +2 and use the split-screen zoom to make it easier to see the fish (although you still may not see a perfect arch).

Good luck Jim off he Catch-22

From: Sawdust Sent: 9/15/2003 6:00 PM
Mike, Old Friend --

Your Garmin a a danged good unit - BTDT - and it's obvious from your post that you have a mounting problem. There are a whole bunch of factors that go into making a good arch -- transducer beam width (usually measured at half-power point), transmitted power, voltage to the unit (which would of course affect trnsmitted power), transducer orientation, etc., etc. Lots of etc.'s. The transducer must be running in clean water (non-turbulent), the transducer face must be clean - with NO slime or growth on it, the unit must be properly adjusted, etc. The list is long, but you spent some good green for the gadget and it should do its job. A well-adjusted transducer should give your forward-facing seatmobile a good bottom read at any speed. In my 22 I could always read good bottom at top speed, down to about 600 feet.

Location on the transom is important. Too close to a trim tab or running strake will screw it up badly; Too close to the prop will cause the prop to ventilate; Too low in the water will cause drag and rooster-tailing; too high in the water will make it skip; The wrong angle will cause leading or trailing edge bubbles. When I was selling the high dollar units to the big offshore fishing vessels -- some transducers costing in the thousands -- it was many days of testing and in some cases, hauling the boat to build a well. -- But, Mike, this ain't rocket science with our little guys.

I'll be in WA DC until the 28th, but after that I'll be happy to come down and work with you. In the meantime, move that rascal from its present lousy position and experiment. Make sure the face is absolutely spotless (some of the commercial guys even use Cajun hot sauce to discourage growth and slime), mount it on a piece of board, whatever, so you can move it around -- and possibly clamp it to the transom so you don't have to drill holes. You should easily be able to find a place where it performs outstandingly. I've mounted one on a trimtab, a la Greg -- and that worked great for me. But you shouldn't have to go that far.

HTH

Dusty

From: Mike Sent: 9/15/2003 8:21 PM
Duster, you done it again. Thanks for your thoughts, and I do not disagree with a one of them. I've already designed in my head the next generation of transducer mounting boards. It will be some high falutin' plastic stuff with a stainless steel plate inserted into a machined pocket that will alow an inch or so of vertical movement and five or so inches of lateral movement without having to take loose the screws that hold the rather flimsy transducer mounting bracket. It's hard to beat the plastic/SS combo underwater! So, that will let me try an infinite number of positions within the area I have to try them in.

The other day, I lowered the bottom of the transducer relative to the hull botom so that it is about 3/16" lower rather than the previous 1/16". That helped a whole bunch on maintainig the bottom lock - it now doesn't lose it until 18 - 20 knots (which I don't often make). It can still go screwy if the water is real sloppy and the boat stands on end occasionally, but it seems a lot quicker to regain an accurate reading. No help with the fish finding, though.

I understand what everyone, including Garmin, is saying about the poorly formed fish arches, and I realize that they won't always appear as such. I do get the vertical lines, and a clear indication of bait balls and the like. But, dammit, for 500 bucks, as an addition to the nearly two grand for the unit, I want arches. Judging by what I have found on the WWW and other discussion forums, I am thinking I should have got the Lowrance stand-alone finder. They get arches which can be easily interpreted. Of course, maybe their software is doing the same thing that the fish symbol menu selection does, but drawing them as what folks want to see. Naw, they wouldn't do that, would they?

One thing about me - I am a stubborn old coot. I will keep dorking around with it until she clicks.

I had some more to say - but they just called me into work again. I don't even have time to check the spelling and grammar.

Thanks to all for your help, and don't stop now.

Mike

From: Sawdust Sent: 9/15/2003 8:51 PM
Mike,

I was a Lowrance dealer and sold a bunch of them. Good unit -- but as I said, this ain't rocket science. The Lowrance isn't any better (or probably any worse) than your Garmin. The electrons go down, then they come back -- the brand name isn't all that important.

I'll give you an example -- a bit idealistic, but here goes. To make an arch, the signal has to be "readable" by the onboard receiver at the forward edge of the cone. IF the transducer angle of radiation is not too broad, which spreads the available power over a wide arc, and IF there is enough power generated by the transmitter, the target fish will show as soon as it's return can be captured at the leading edge of the cone. Then, as was stated before, as the target approaches and then leaves astern -- the time factor of the transmitted/returned signal makes the arch as it leaves the aft part of the cone because of the difference in time. No magic.

Let's face it, these little gadgets are LOW power. 600 wats (p.e.p.) ain't gonna blow many fuses. When you spread that signal over a wide arc, the edges of the cone get nearly zilch. I can put that in real numbers, but that's frightening. In my opinion the Garmin as as good as any of them with the same amount of transmitted power -- this is a very competitive industry, and receivers are nearly equal unless you are willing to spend big (beeeg) bucks. If your transducer is properly positioned you will get arches. Sometimes. If you are not directly over the fish -- and one never knows -- you may not get enough signal to make an arch. Just a dot, or mark. So I'm outa here.

It WILL work.

Dusty

From: Chuck S Sent: 9/16/2003 8:20 AM
Dusty --

How 'bout thru hull mounting the transducer(s)?

-- Chuch

From: Sawdust Sent: 9/16/2003 9:41 AM
Chuck,

I've done that on my own boat (s) -- the answer depends on what you must shoot through. Hand-laid glass, if rolled out properly, doesn't seem to attenuate too much signal. A cored hull, on the other hand, is a tough one. We used to anchor the boat, then move the transducer around to find max signal -- and that's a hit/miss proposition. A flush mount works great, if properly installed, but of course there is always the possibility of trailer damage. Many of the smaller commercial fishing guys build a box (well) inside the hull, then trim the inside of the hull where the transducer will be located so that there is a single layer of glass to shoot through. Of course most of the inboards use an externally mounted transducer, and drill a hole for the tube. Downside there too, because when the transducer face gets foul, you must either haul the boat or dive to clean it. Because you can't use antifoul paint on the transducer face, the transducer quickly lose signal in salt water, particularly in FL, or other warm water situations.

I like the transom mount for our little guys, and it is rare when you can't get one to work satisfactorily. And that's not without lots of drawbacks. I've only had one mounted on the trim tab, as Greg does, and it worked very well, but it picked up seaweed badly. In my installation I used a huge commercial transducer and just drilled a hole in the tab for the mounting tube. Greg suggested a mounting bracket on the aft edge of the tab and mounting a conventional transducer. Should work very well. Perhaps the best of both worlds.

Some of the manufacturers used to made a place where you could shoot through the hull -- then glue the 'ducer to the inside of the hull -- not sure any do now.

Long answer to a good question!

Dusty

From: Chuck S Sent: 9/16/2003 1:44 PM
My racing sailboats have all had thru hull transducers located about 1/3 of the way aft of the bow. Displacement hulls for the most part. Rarely see this on motorboats.

I was hoping the lil' sump on my 16 Cruiser wasn't cored, but it is, so shooting directly thru the hull seems out. I'll have to check on stern mounting plates, they're easier to move the transducer around than direct hull mounting.

-- Chuck

From: Chivita Sent: 9/16/2003 9:30 PM
Mike,

I finally got my Garmin and GSD 20 to work, but have not yet tried the arches, I was just so happy it worked I forgot to play with that part.

When I originally connected the GSD 20 my GPS kept shutting off, usually when I hit a wave or got bounced around a bit. Definetly a bit unnerving when you lose your chartplotter in the middle of a tight spot. Mine, like yours, also would lose the bottom at any speed above 6 or so knots. I rewired the dang thing several times, lowered the transducer and never got anywhere. When I disconncted the transducer, my problems went away, but so did my depth, etc. It sounds like you had the same transducer as I had as well.

After trying all of the above, I figured I'd try a different transducer and bought the cheap one without a 'speed wheel' . West Marine claims transducers rarely go bad, but SUCCESS! Don't know if that is the issue for yours, but my system finally works. The second transducer looks identical to the first, but without the wheel, it uses the same mount so I didn't need to drill any additional holes either.

Feeling like a hot shot, I connected the GPS to my "DSC" VHF and that part works like a charm too! I'll have to admit my wife is getting a little tired of me going out to the boat at night just to turn all the goodies on and watch them interact! Next is the autopilot connection and I'll be set. Hopefully I'll get out this weekend and check on the fish arch portion. I'll let you know what I find! When this funky GPS setup works, it's really quite impressive!

Chivita Dave

From: Redƒox Sent: 9/17/2003 10:32 PM
OK I confess the reason for me wanting to mount it on the trim tab in the first place, was the fact that (in the days I did not have a tender) that I banged up too many t'ducers, beaching the boat... arrrrrr!!