... for a Humminbird Helix 12 HW graph.
I have tried the in hull, the transom style but for the life of me after I get over 25mph I lose all contact with my depth readings. I'm only need it for reading my depth while on plane. I already have the Y cable to the transom mount so I am looking drilling a hole in my hull and putting in the thru hull type.

Can't you get a shoot thru hull for your boat if its a glass glass boat

Already tried that, it still goes out after 25 mph or so. That was my first transducer attempt. Second was a transom mount and it does a little better but not really anything above 30mph.

When it comes to transducers 99% of issues is the install. Can you post pics of your current transducers, What kind of boat? The majority of Bass boats have shoot thru transducer that easily work up to and above 70 MPH. There has to be more to this to be discovered.

The boat is a 2020 Nitro Z20. I installed the in hull transducer right in front/next too the factory in hull transducer in the hull.(The factory one is a Lowrance, I’m using Humminbirds)
I lightly sanded the hull and the transducer face and put down the epoxy that came with it. It twisted the transducer a good 1/4 to 1/2 turn and put a brick on it for two or more days before removing it to keep it snug to the hull.
The placement in the hull is flat, I am assuming that the factory guys knew where to place the Lowrance transducer when the put it in...remember I’m assuming this...lol.
It about 14” from the back of the back, (transom) so I know it is staying in contact with water even on plane.
The transom mount is mounted flat and halfway down below the hull and on the smooth surface where no ribs will create any type water disturbance.
I first thought it might be a bad Y cable so I bought another one but that did not help it any.
I can take a picture off the transducer but that will have me take out 3 batteries and unscrew the board to access that area. If need be I will do that to correct any problems. I would have to do that anyways to install a thru-hull transducer.

Looking at the transom from the back is the Transome ducer on the left or right of the motor?

Also the farther you mount the thru hull transducer from the transom the worst it will be for connecting to the bottom. Also did you test the location in the water before glueing it down? To make sure it locks on>?

It s just about center of motor, this is the in hull transducer. My transducer I mounted on the transom , it is on the right of the motor.

I did not test it before I glued it down. I put it right next to the factory install in hull transducer .Again I was assuming the factory guys knew the best spot. It is a flat area in the hull , I'm sure a place where Nitro made just for in hull transducers.
What I have done is ordered the tru-hull transducer for my Helix 12. I will not have more than a 2 degree rise so it will be pointed almost straight down.
Being most of what I fish is the Coosa River chain I really like knowing the depth I'm running at. You can be in the middle of the lake portion and be running in 40' of water and the next second you are in 2' of water. I do rely on my Lakemaster map the entire time but my OCD kicks in when my depth reading are reading nothing or 20' to 650' all the time.

If you can post a pic of your skimmer transducer on the right of the motor with a view of from behind the boat looking at the ducer and on the side of the boat along the transom from the ducer side of the boat I might be able to see if something jumps out.

Will do, thanks. I will have to take a picture when i get home this evening.

borrow someones lowrance and see if the one that came with the boat reads while on plane- if so, get the adapter and just use it.

A Lowrance transducer does not do HW CHIRP.

(Update)
I installed a thru-hull transducer. Drilled that 1 1/8" hole and installed it. Waited a few days for the marine epoxy to set and tried it out.
When i get over 25 0r 30 mph, I lose all depth readings! I give up on trying to get a transducer to read depth while on plane.
I have tried a shoot thru, a transom mount and now a thru hull and every one of them all lose depth reading after that speed.
The sonar part is very clear and the depth reading is fine while sitting still and going slow, but so were the in hull and transom mount.
I will just rely on my Lakemaster mapping to navigate the waters and worry about depth when at idle or sitting still.
The thru-hull is mounted near the back of the boat, and a very clean part where I am not getting any turbulence from the underside of the hull. It is on a 4 degree slant which is fine as long as it is under 10 degrees per Humminbird install directions.

One thing, is there a setting on the sonar side that might be better when you are on plane? Like narrow beam, or wide?