Boat Speed & Sonar Image

For folks with shoot thru the hull transducers.

At what boat speed do you begin to lose bottom image?

Me... HDS 12 Gen 2 @ about 45MPH.

Don't understand why. The hull transducer is suppose to give the best reading at high speed as there is no turbulence and it is always in the water. All I can figure is the placement is wrong or you have a void under it in some way. Pour 5 gals. of water in the transom of the boat and see if that makes a difference while up and running.

There is always turbulence; speed doesn't negate it. (Even a jet traveling at near Mach 1 has aerodynamic surface turbulence.)

You cannot avoid losing the bottom signal at some point as speed increases. One reason is because the boat moves after sending the string of ping signals to reflect off the lake bottom. When the signal packet gets back to the surface, the transducer isn't there; it has moved slightly. The faster the boat is going, and the deeper the water, the farther "out of position" the transducer is. When this happens, the transducer's new position isn't ideal. Signal amplitude falls off very rapidly as you move away from the transducer's position when the ping pulse was released. The data also becomes distorted because the angle to the transducer's new position distorts the data indicating what was on the lake bottom.

Is that the fastest you could get when testing BEFORE you attached the transducer to the hull?

The fiberglass bass boat I used to have had a max speed of 68.4 and I never lost the depth reading or bottom image.
The last boat I assisted with a shoot-thru installation got over 72 mph with no depth loss or bottom image.

I have same issue with mine. Once I hit 40 or so I lose depth. I don’t think mine was installed right. Came with boat new.

My boat holds til 60mph, but I have a heavy deep V hull Champion. My Skeeter used to lose it about 55, caused by over trimming your boat. The hull gets so high that the sonar is trying to shoot through the air under the hull.

At anything over 40mph it's useless. You have already passed it by 100s of feet. If you're worried about depth use your mapping. If you're looking for stuff running under 40mph is fine.

If you loose your depth @ speed your through hull transducer is glued into the wrong place.

That’s what I was told or the glue could be causing interference. I don’t even know where the transducer is lol

I completely lose my sonar at anything beyond idle. If I'm on plane it reads nothing.

Unfortunately same here... I have my mapping to help on new lakes that I don't know but wish I had the sonar at least when on plane. Could use the depth reading every once in a while!

So the glue might be causing interference at speeds above 40 but not below 40? Isn't the glue the same all the time? If so how could what you say make any sense?

What's likely happening is that hydrodynamic turbulence develops at speeds over 40, and that turbulence affects the hull area where your transducer is looking through the hull toward the lake bottom.

Then yours is installed 100% wrong.

Skeeter used to cut about an 1/4” deep spot for the “shoot through the hull” transducer puck to sit into. It wasn’t quite far enough back, so while trimming up a person introduced air under the hull. If you trim down all the way, you will regain the bottom contact on the graph. Now with that written, I’m convinced nobody on here other than Flippin’ & me reads any of the responses.

Same problem with manufacturer installed through hull. Bought new graph and transom mount transducer, works up to 10MPH now, on plane reads 200+.

Again that’s what I was told from a person that installs them. I didn’t make the claim...

If silicone was used, then maybe or if a really fast drying epoxy that was filled with air bubbles was used. Need a slow drying epoxy that lets all air bubbles dissipate before it dries. Not sure why I’m writing this, because nobody ever listens.

All I know is; when I back off to 60 MPH that boat better be giving me a reading of depth while also using the map. If not it is going to someone that knows their stuff. I have only had one Skeeter that the dept fell out and it was fixed. Don't have a clue what they did in Odessa; but never had another problem.

Mine will read until about 60, then the hull starts to lift. If I'm worried about the depth, I don't need to be running any faster.

You might want to check to see if your transducer is still glued down correctly. Mine wasn't getting good signal at speed, and I found that it had come un-glued from the hull. While mine was back there not glued down well, I noticed it did better if there was a little water in the hull.

I also think that the quality of the water affects the signal as well. Mine reads well on Rayburn and T-Bend, but doesn't show well in the mud of Livingston.