Garmin Sonar Not Reading Bottom at Speed

[Caburke1]

Here's the equipment: 2019 Canyon 306
Garmin GPSMAP 8616xsv
Garmin (Airmar) B164 1kw Tilted Element Transducer

This is a dual frequency transducer and it struggles then fails to read the bottom when I'm on a plane. The 200mhz will show a broken bottom display but will give me a depth number until I reach anywhere from 130' to 600' then it fails, just flashing the last depth number. The 50mhz doesn't read at all at speed and won't even give me a depth number. I had the Garmin Rep out and he tested the transducer and it's fine (he was here representing the electronics installer so didn't share much info with me). I spoke to Grady Corporate and was told they recommend installing the thru hull transducer on the molded in pads. My 1kw transducer is too big for the pad which they are aware of and they recommend it be installed through the hull with no detail. I spoke to the dealer and they said the problem is the result of air turbulence interference and that it's a known problem with Grady's. They're recommendation is to install a second transom mounted transducer. I had this same style transducer on my 2008 273 Chase and it worked really well.

Help! Is this really a known problem with Grady's? Are there other changes I can make other than putting a transom mounted transducer on my boat? They're recommending either the GT41-TM or GT51M-TM but i've heard them described as a "clown shoe" because they're so big.

Any guidance from those of you that may have had a similar experience or are knowledgeable on marine electronics?

 

[SkunkBoat]

My Gt51 TM between my motors doesn't work at all on plane.
The side vu is excellent though at slow speed.
The down vu is not quite as good as the B744 thru hull (when its clean)
My B744 holds bottom on plane similar to what you describe

 

[Bdsp1234]

I don’t have your model Sonar, however after speaking with Garmin, they gave me the instruction on how to set the gain for higher and low speed along with the hertz settings. I’ll have to go back and research before I pass the info along because I don’t remember the specific. It made a huge difference. Shallower in Shore vs off shore is quite different.

 

[Caburke1]

Bdsp1234, I will appreciate the help.

Skunkboat, thanks for the information on the transducer. I'm only looking for readings at speed and I don't want to spend the money if the transom mount doesn't read on a plane.

 

[seasick]

My transom mounted dual freq transducer only works well in shallow (5 ft or less) if configured at 200khz. It was a duh moment when I figured that out after adjusting the angle about a dozen times The head unit is a Lowrance HDS
.

 

[wspitler]

My transom mounted dual freq transducer only works well in shallow (5 ft or less) if configured at 200khz. It was a duh moment when I figured that out after adjusting the angle about a dozen times The head unit is a Lowrance HDS
.

If you haven't already, check out the SternMate website for discussions on placement. I have the Garmin 94SV with the GT51TM transducer and it reads great sideview and traditional chirp after a couple adjustments (SternMate mounting system) up the about 60. ' Different freqs but similar.

 

[Lt.Mike]

Below is a copy of the specs for a Navico 3 in 1 transducer for Simrad and Lowrance. The side scan and down scan are lost around 10 mph and faster. The conventional sonar should operate as long as it’s in the water and there’s no cavitation.
here are three videos to consider...

When this fellow speaks I listen, mik