Marine: Boating, Sailing, PWC, GPS and Navigation - mountin a depth finder on pontoon boat

i recently bought a depth finder ,the intruction does not tell where to mount the transducer at can any one please help

If it were me I would make a bracket from 1/8 inch metal strap and mount it to the crossmembers between the pontoons. Have the finder at the depth of just below the center of the pontoon. Also do it near the front of the craft.
Run the cable from the console to to finder through the deck or over the deck whichever you desire. Just be sure you attach it to the craft so debris in the water will not catch the wiring and pull it loose. I would use thin metal for the bracket so it could bend in case it hits something.

I find it hard to believe there's no mention in the installation instructions. What kind of depth finder is it? You should be able to get the manual on line for it.

Personally, I would mount it just below the water line at the rear of one pontoon. You may have to fabricate a bracket - though most depth finders come with a screw on bracket that should work easily. I prefer the rear of the boat as the front of a boat tends to bounce, thereby causing false readings... Plus - when you're in "tight mode" measuring inches instead of feet - you always know how much depth is under your prop.