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View Full Version : Garmin 740s Only Getting to 300ft?????



Scurry
10-27-2011, 04:41 PM
My 04 Contender 23T was originally equipped with a Furuno sounder. The unit crapped out so I thought I was upgrading by getting a Garmin 740s. BIgger screen, touch screen, much more detailed chart plotter. The boat is factory installed with an inhull transducer. The Furuno used to read up to about 1200 ft before it stopped reading and started blinking. The new Garmin with the same transducer stops reading and starts blinking at 300 ft. I contacted Garmin and they are saying the transducer is not powerful enough. The more powerful transducer is like $2K+ Is this correct? Or do I need to switch to a thru-hull?

fish_stix
10-27-2011, 06:16 PM
You can use a shoot through (in-hull) transducer if your hull is solid fiberglass, otherwise you need a through hull installation. Garmin's website lists several transducers for the 740s, you will need a 1KW to get the performance you bought. Always best to follow the manufacturers recommendation for their units.

Renagade69
10-27-2011, 08:24 PM
Get the 1 kw if you need allot of deep readings. The 740 will switch to 1000 watts with that transducer. It is much lower output on the smaller transducer.

MER
10-28-2011, 07:29 PM
Almost any sounder will start to lose the bottom at those depths when set to 200 kHz. You need to make sure your unit gets switched over to 50 kHz for deep water operation. In my personal experience with Garmin sounders I've always found it necessary to manually adjust the fishfinder to at or near maximum gain to get the best results. I have installed and reviewed Garmin 740s (http://www.marine-electronics-reviews.com/garmin-740s.html) combos and found them to work very well. Not sure what transducer you are running but as always that component will play a major role in the performance of your sounder.

Idlewilde
10-28-2011, 10:46 PM
Almost any sounder will start to lose the bottom at those depths when set to 200 kHz. You need to make sure your unit gets switched over to 50 kHz for deep water operation. In my personal experience with Garmin sounders I've always found it necessary to manually adjust the fishfinder to at or near maximum gain to get the best results. I have installed and reviewed Garmin 740s (http://www.marine-electronics-reviews.com/garmin-740s.html) combos and found them to work very well. Not sure what transducer you are running but as always that component will play a major role in the performance of your sounder.

X2. Your Furuno would not read/mark down to 1200 ft when set on 200 kHz.

Scurry
11-01-2011, 02:47 PM
Thanks guys...Not sure if the transducer is 1KW or not. it's the one Crook & Crook sold me with the unit. I'll have to check the specs on the box. I will start by adjusting the gain since I'd rather not buy another transducer. I just bought this one in July.

Boattronics
11-04-2011, 08:47 AM
Your ducer should read much deeper. You said the Furuno stopped working, and you traded it for a Garmin, which isnt working properly either. From what you are saying, with an in-hull transducer, I would bet money your ducer has developed a leak. It is full of mineral oil (or should be) and sometimes they can leak, or the cap off the top can pop off and the fluid can spalsh out. (depending on which model it is) Once the fluid level has fallen below the bottom face of the ducer that is inside, it can no longer properly focus the beam through your hull, and will no longer work properly. Examine your ducer so you can describe to me which one it is, and I will tell you how to check the fluid level.

Scurry
11-08-2011, 06:01 PM
Boatronics...the transducer is brand new. I bought it when I bought the Garmin...it's the same exact ducer that was installed with the Furuno...but the plug wasn't compatible so Crook & Crook sold me the same one for the Garmin. It's not 1kW. It's a 600W AirMar p79.

Plane Fish n
11-08-2011, 11:27 PM
Scurry,

Both Tony (boatronics) and MER are giving you excellent info.

I have a Garmin 740s installed with the GARMIN 010-10192-01 Transom Mount with Depth, Temperature and Speed transducer.

I also have a Garmin 541S installed as a backup.

It is actually made by Airmar and I can run at 25 kts and it will read to about 750' before it starts to flash.

If I slow down and make sure it is switched to 50 khz vs 200 khz (the auto function doesn't work very well), I have read up to about 1200' before it flashes.

I'm not sure.. but Tony...jump in here.. but I would check his mount on the transom to make sure the ducer is not too high or too low.

That could be critical.

Good luck and if none of this works, you can always call Garmin Customer Service 1-800-800-1020

Boattronics
11-15-2011, 11:01 PM
You said it is a p79. Bingo!
Just as I suspected, you have an IN-HULL transducer problem, most likely caused by a leak of the fluid in your transducer mount. This transducer uses a small round disk that is bonded to the hull, and then filled with mineral oil. Then the puck is fixed into this resivior. If the fluid leaks, the transducer will not work properly, and I would make a cash bet that is exactly what you have going on right now.
Sometimes, we fix that ducer to the hull without the oil resevior. A glob of silicone, with the ducer pushed down into it removing any air bubbles, will achieve the same result. If your resivior has developed a leak or wasnt installed properly, you may just want to re-install with silicone alone. This works very well and has no chance of leaking in the future.

Plane Fish n
11-17-2011, 11:35 AM
Scurry,

You there?????
:Popcorn:Popcorn:Popcorn

Scurry
11-18-2011, 11:27 AM
Yep. I'm here. Sorry. I checked with my mechanic who installed and he assured me it's installed correctly with the oil and all. He is saying the ducer is not powerful enough to get the depths I am hoping for. :banghead

Boattronics
11-19-2011, 01:27 PM
Yep. I'm here. Sorry. I checked with my mechanic who installed and he assured me it's installed correctly with the oil and all. He is saying the ducer is not powerful enough to get the depths I am hoping for. :banghead

I wonder if he actually checked the fluid level, to make sure it was still level?
I know that boat, that ducer and the 740s, and trust me, when properly installed it will read much further.
There is really no other variables, the 740s has been virtually bulletproof with no issues. Ive been doing this a long time, and the problem you are describing is a ducer install issue. Sounds like its time you get a marine electronics tech. to look at it!

Either way, thats a great boat and a great machine. Maybe it's time to take better advantage of it and get an airmar 1kw tilted element transducer? Its a thru hull, that is flush with the bottom of the boat. No worries of trailer or drag issues. No loss from shooting through the hull, much greater power and sensitivity. You would be much happier with its performance and will work great in depths over 1000'.

Plane Fish n
11-19-2011, 04:41 PM
Yep. I'm here. Sorry. I checked with my mechanic who installed and he assured me it's installed correctly with the oil and all. He is saying the ducer is not powerful enough to get the depths I am hoping for. :banghead

I think Tony is giving you sound advice regardless of whether you use him or another Electronics Technician.

I KNOW that your 740s will pick up depths much greater than what you are getting.

Good luck.