Depth Finder Blinking in Shallow Water

[Brian 27 OB]

Refilled the puck with antifreeze then tried mineral oil and still get the blinking depth when we are below 7.5’. Deeper water and at any speed it works fine. Anyone run across this? Happens in both fresh and salt water. I can change all the settings from auto to shallow to changing the frequency and nothing seems to fix this. I’m thinking of just buying a new sender or replacing the GT15M-IH with something else. I did see that the factory didn’t align the arrow with the notch and was thinking that would have an effect but it didn’t.

 

[BB marine]

I have never had this problem before until I started cruising in Florida. Shallow water and disturbed water seems to make the transducer pick up false readings. Mine doesn't go bad until 5' then it will show 1.9FT-1.7FT-1.9FT start blinking then go back to reading normal. It is very erratic and does this when it is most needed. I have changed settings, reset to factory settings, changed from 200HZ to 50 HZ, checked and the fluid level and added each time just to make sure it is full. There is no evidence of a leak. I'm not sure if there is a glitch in the software or transducer is failing. I have a P79 transducer and a 7612 XSV Garmin plotter.

It works fine in deeper water.

 

[gwishon]

I’ve found that when this occurs if I set the depth range manually to something close to the actual depth instead of ‘auto’, the blinking will stop and you’ll get an accurate reading. In your example, try a setting of 10 ft.

Gordon

 

[S@LTD]

I had this happen once when I didn’t do my Garmin updates. If you haven’t done this in awhile it might be worth a try.

 

[knotflying]

I have this occur as well in shallow water and if following someone and there is water disturbance. I did look this up on a search and found that adjusting the setting helps somewhat. Now I can't remember specifically the settings. It is unfortunate that it happens when you need it most, in shallow water. On the west coast they panic when depth gets to 20 feet. Many times I am looking at 5 feet. :lol:

 

[Brian 27 OB]

I called a local shop to have a mechanic/garmin tech look at my transducer, amazingly they had someone already at my marina today. I drove an hour to get there, and after 10 minutes and some investigating she said the GT15 was getting harmonics from the hull material and adjusting the settings with the chartplotter would not be able correct it. I wasn’t about to argue that conclusion, I just want a depth finder. So I was sold a transom mounted transducer that compliments the in hull one. The transom mounted version might lose bottom at higher speeds but the inhull one will take over at that point (will still be useless in shallows at all speeds). Transom mounted transducer GT-30? also offers some cool sonar and scanning that I will probably never use regularly but could be fun to check out. They haul and install sometime in June if I’m lucky. Good thing I have extra props to get by on.

 

[knotflying]

I won't argue the harmonics issue, but would have a questions. Why would depth make harmonics different to cause the problem? If the problem persists after the install will they refund the money? Will a stern mounted transducer work with the turbulence created by an inboard?

From Garmin site: While it is not recommended that more than one transducer be run simultaneously, there can be multiple transducers installed on a boat.

If two transducers are transmitting at or close to the same frequency and the signals cross, interference may appear on the display of your Garmin Marine Chartplotter. For best results, two transducers need to have at least a 50 kHz difference in their frequencies to not cause interference.

Some chartplotters will share their built-in sonar with a compatible chartplotter. This allows for a single transducer to be shared through the Garmin Marine Network. See Marine Network Sharing Compatibility to check for compatibility of specific chartplotters.

 

[fishheadbarandgrill]

When in shallow water and the sonar loses tracking I will go to a full screen on the sonar where I can see the bottom. Usually happens when I get to about 2 ft below the keel.

 

[Lucky333]

I just bought a 2016 Cutwater 24 with the same blinking problem. After talking to Airmar, Garmin and Cutwater I am as confused as ever. I need to read depth accurately less that 10 feet. One thing I noticed is that the Transducer is supposed to be level (port to starboard) and it is not even close. I estimate at around 25 degrees. I am confident the base of the P79 is installed incorrectly so that no matter how you try to adjust the cover/ transducer it can never be level. The high side of the P79 base should be on the lower side of the keel it is installed so that the high side is on the high side of the keel. I am buying and installing a new base to see if that helps. Can anyone else confirm what I am seeing?

 

[Lucky333]

I should have written he high side of the P79 base should be pointing or closer to the keel and it is not. Sorry for the confusion. Is anyone's P79 level port to starboard? Mine is not.

 

[Alpina]

. On the west coast they panic when depth gets to 20 feet. Many times I am looking at 5 feet. :lol:

I panic at 20’ also on Lake Lanier in Georgia where water depths are in the low hundreds, except when I’m anchoring.


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[CruisingElvinRay]

I panic at negative numbers on the Atlantic ICW.


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[Submariner]

So I was sold a transom mounted transducer that compliments the in hull one. The transom mounted version might lose bottom at higher speeds but the inhull one will take over at that point (will still be useless in shallows at all speeds). Transom mounted transducer GT-30? also offers some cool sonar and scanning that I will probably never use regularly but could be fun to check out. They haul and install sometime in June if I’m lucky. Good thing I have extra props to get by on.

I'd love to see a picture of the location they mount your transducer on the transom of your R27-OB
I've been looking specifically at the GT51M-TM for a transom mount. The thru-hull transducer is nice and works, but I'd rather it were near the transom so I can see our shrimp and crab pots on the bottom (helps to know when they're off the bottom when pulling them when we can see them on sonar).

 

[bob daily]

This is what I do to correct the loss of depth in shallow water. I change the frequency to 200 kHz, the 50 kHz is sometimes too strong in shallow waters. I put the range setting in auto, then manually adjust the gain sensitivity to decrease the way the transducer reads stronger returns signals in shallow waters. This has worked for me in the past and hope it helps! Bob

 

[Lucky333]

Just wanted everyone to know that I corrected problem by buying a new base and installed it correctly so that the transducer top is now level port to starboard. If anyone needs help on this don't hesitate contacting me at donfontaine8@gmail.com. Now getting good readings to 3 feet.