Goto Airmar at:
http://www.airmar.com/
and look up the spec’s on the “P79", or search
Raymarine ST60, or Navman.
They’ll have installation instructions, dimensions, wiring diagrams, etc.
Ps:
There are several different transducer diameters, but (I belive)
Raymarine usually uses the 2" dia (mayber 1-11/16").