That's for the solix/onix..

This one is what you need for helix transom mount. https://www.humminbird.com/Products/XNT-9-20-T/


This one is cheaper. It doesn't have temp but you don't need temp from this transducer if you are using the y cable. You will get temp from the si transducer.

https://www.amazon.com/Humminbird-710214-1-Transom-Transducer-XNT/dp/B000MPO8R4

Thanks that's what I needed to know

For high speed epoxy that in the hull.

Another option to see your depth if you loose it at high speeds is to simply follow the depth on your charts. This is what I do as I have an aluminum boat and the in-hull transducer is not an option. Following the depth on my charts works just as well as seeing the depth read-out on my unit.

Alumaducer is the only shoot thru option for aluminum boats

http://www.vexilar.com/pages/home

I simply look at my charts....problem solved.