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Thread: Garmin GPSMap 498 Question

  1. #1
    Member patrickL's Avatar
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    Default Garmin GPSMap 498 Question

    We recently purchased a boat with a Garmin 498 GPSMap Sounder on it. The specs call for it to have a range of around 1500ft. However, I can't get the sounder to register much over 100ft. I know their is a depth range setting so the screen stays in a certain depth range but the depth reading basically quits working after it exceeds 100ft. Does anyone have any ideas why this is?

    Also, the sounder doesn't work at all at speed. I'm guessing the transducer needs to be lowered so its catching clean water at speed. Is this correct?

  2. #2
    Member L. G.'s Avatar
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    Default

    Run it in AutoDepth mode. Use the menu once your in the depth sounding mode.

    Mine craps out between 600-800 feet.

    I'm not trying to fish or crab at those depths, so it's no biggie to me . . .

  3. #3

    Default I have a 498

    I have not been overly impressed with the sounded, looses bottom way to fast and starts blinking. If the transducer gets air bubbles or any thing in the way I know they stop.
    I plan on mounting the transducer by using there special glue to the bottom inside of my Bayliner. Not going to buy the special one as a commercial guy said they just use the standard one and glue it in. Very careful not to have a bubblein the glue, very important!! Makes the bottom of the boat a reciever also.
    Thought about calling them and asking whats up.

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    Member Akgramps's Avatar
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    Is this "special glue" a Garmin product?
    ďNothing worth doing is easyĒ
    TR

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    Member Rod in Wasilla's Avatar
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    Special glue? I've heard of people bedding their transducers in silicone. Seems to work great as long as they're careful to not get any air bubbles in it. I have mine in an oil bath. Works great and no bubbles to deal with.
    Quote Originally Posted by northwestalska
    ... you canít tell stories about the adventures you wished you had done!

  6. #6

    Default Special

    I understand it to be a special product, the material has to be able to not block, diminish or impead the signal at all, and the instructions say how importand no bubbles is. A lot goes into the surface prep of the floor of the boat. I didn't do first time out as it was time to get her in the water.
    What he told me was to just mount the unit that came with my Garmin that was, I was going to buy another one (off e-bay cheap) and mount it just in case I failed to get it right.
    Hope some one else has info on other ways, how would you keep the oil in one place, and silicone?

  7. #7
    Member Rod in Wasilla's Avatar
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    Thumbs up Oil bath method

    I took a four or five inch (don't remember... it was the smallest size that the 'ducer would fit in) threaded PVC coupler and cut one end of it in a slight wedge shape to fit the bottom of my hull. After cleaning the area well, I glued the coupler to the hull with 3M 5200. I also slotted the top side of the coupler a couple of inches to allow the cable a way to get out. Then I set the transducer in it, sealed the cable into the slot, filled it with light hydraulic oil, and screwed a cap on. It works great. And if I ever have to replace the transducer or move it to another boat, I don't have to deal with it being glued down. If you run the boat in Florida you could substitute the oil for water. But, that just doesn't seem like such a great idea up here in the frozen north.

    To use silicone, you just cut the whole end off of a tube (the kind of tube you would use in a caulking gun) and push out a fair sized "lump" of the stuff onto the hull (after cleaning, of course). Then you set one end of the 'ducer into the silicone lump and rock it into place using only one smooth pushing motion. The hard part about this method is keeping all the air bubbles out while setting the lump, and rocking the transducer in place. I hear it works great if you do it right. And, I think you need to use clear silicone for this to work. But I'm not sure about that.
    Last edited by Rod in Wasilla; 08-20-2009 at 16:27. Reason: Added the silicone method
    Quote Originally Posted by northwestalska
    ... you canít tell stories about the adventures you wished you had done!

  8. #8
    Member patrickL's Avatar
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    Thanks for all the info. I will give the settings a try. I have a Hewes so I don't think the ideas you guys are talking about will work. Does anyone know?

  9. #9
    Member Rod in Wasilla's Avatar
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    You're right. Mounting the transducer inside is for 'glass boats with at least some portion of the hull uncored.

    If you're not getting a good reading on your transom mounted sounder, an adjustment will usually take care of it. It should be mounted in clean water (not directly behind a chine, not right next to a trim tab, etc.), just below the bottom of the hull, and angled slightly forward. And usually, a little too low is better than a little too high. The idea is to have nothing but water under the 'ducer at speed. Air bubbles kill the signal.

    If it's still not working right, check for good wire connections. And check for any physical damage on the 'ducers housing. Also, check the settings in the head itself, like sensitivity, gain, range, or whatever. Once you've verified everything you can, you may have to break down and get it looked at by a professional.
    Quote Originally Posted by northwestalska
    ... you canít tell stories about the adventures you wished you had done!

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    Default Garmiin Product Support - Call Them / E-mail

    I recently had a problem with a Garmin 188 being a few miles off on the readings. An E-Mail to product support at Garmin resolved the problems. (needed at update and reset the auto locate)

    garmin.com or 800-800-1020 or the guy I worked with was Kevin Ellison at 913-397-8200

    From what I have learned, the angle of the transducer means a lot on getting a signal back on speed. Keep in mind the signal has to bounce off the bottom and still be able to return to the transducer at the speed
    your traveling at.

    Good Luck - I am sure they will help you
    Last edited by akfishnut; 08-21-2009 at 21:11. Reason: spelling
    How stupid is it to be wasting tons of salmon and halibut as bycatch in the Bering Sea and then have the coastal villages hollaring they have no food? It's got to stop!

  11. #11
    Member Snagger's Avatar
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    Just fork out the money for a 1KW airmar through hull ducer.

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    Member Cap'n Ron's Avatar
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    Default I have that Garmin 498 and it is fine.....

    But now and then the transducer gets tipped up then it blinks and takes a long time to find the bottom. I've tightened it and that may help, don't want to hit something and have it break off.

    If you have trouble figuring how to do the settings etc (tip to use auto is great, that's all you need) PM me and I will set you up with my personal technical expert (15 year old son) that knows everything about that GPS.

    You should have the map setting on anyway when you are going fast. It shows all the rocks, and water depth in general with shallow areas in blue, deep areas in white, low tide exposed ground in green etc. Learned that the hard way *****in about the sounder not working at high speed and hit a rock 200 yards from shore that I now know shows up on the map setting!

    Mine is on a Hughes too. When the transponder is at the correct level it works great. As soon as I switch to sounder and start to slow, it picks up the bottom. Haven't been in over 800 feet of water, but you won't fish or shrimp that deep or deeper, so it doesn't seem to matter!

  13. #13

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    Snagger, what kind of fish finder did you hook up the 1kw transducer to? I am wondering if it is going to do any good to hook it up to a less powerful unit? If it is , I am going to order one for my Garmin. I know a good transducer makes some diff., but don't know any body that has tried one.

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    Default check the FREQ settings...

    I did not have time to read everyone's replies but as I scanned them I don't recall seeing any suggestion that you may have the unit set on the wrong FREQ.

    If I recall correctly I believe this unit has dual freq. You can select 50Hz or 200Hz or dual...

    50hz has better depth capabilities
    200Hz has better detail capabilities

    Also double check to make sure the transducer is of the correct freq.. The transducer needs to be matched with the unit...

    Good Luck

  15. #15
    Member patrickL's Avatar
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    We went out yesterday and tried out some of the suggestions. The auto depth seemed to solve the problem. On my old Lowrance I could set the depth at say 100 but it would still record the real depth. It just allowed me to see in detail the top 100ft and still have it tell me the total depth. Great for looking for suspended fish.

    Anyway, seems to have taken care of the problem so I appreciate all the help. This unit has some nice features, like dual freq., that my lowrance doesn't. Overall though I'm not overly impressed but it gets the job done. Thanks for all the help.

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