I use an digital angle gauge to measure it. You can do it on the inside where you plan on mounting it. It should be pretty close. I would use a tilted array transducer. The array inside the housing is put in at an angle so you donít have to mess with a block to get it vertical. I have put them in several boats and havenít had any issues.
If you are one there is no explanation necessary.
If you arenít one, there is no explanation possible.