About 2ft....Where ever you can access it easy from inside and it's not in the way of other things.
Drill a 1/8in pilothole from the inside to the outside. Then a 1/4in hole. Then drill using the holesaw from the outside going in.
http://www.airmartechnology.com/2009/ma ... esults.asp
The SS 60 is available in 0degs for 600watt
The SS 164 is available in 0degs for 1000watt and both are very easy to install.
I'd check with Jim @ BOE for these , but I bet either would have to be ordered. They are not as common as the B 60 or B164
One more thing to add:
When you order the X-ducer. Ask for a "Mix & Match" unit.
What is Mix & Match?
It is a X-ducer that has a 6ft cable on it. Then there is another cable that connects to the X-ducer cable [20?]ft long] and to the head unit that you specify. [Garmin,Furuno, etc,etc]
You ask why do that?
Your planning for the future. Lets say you just bought this Kick-ass Furuno unit and you decide to sell your boat to get a bigger boat. You can keep your Furuno and the new owner can put a Furuno on the boat. But lets say the new owner like Garmin better. All he has to do is change that cable. The X-ducer stays the same.
The Mix & Match cost no more you just have to ask for it....You will not find this info in any book.