I have the Yamaha FX140 Waverunner which is shown on your packaging of the DF11205 and I need to know where to place the transducer. Follow

The best place to mount the transducer on most PWC's is inside the hull, under the engine. Using
the Installation Manual  follow the instructions under the section titled "In-Hull Mounting The Transducer". Make sure to test the location as per the instructions before using adhesive to permanently affix the transducer. Some
PWC hulls are composite or double hulled and the transducer cannot be glued in-hull. The only way
to know for sure if your hull is one of these is to contact the manufacturer or use the test method in
the manual. If the test methods DO NOT allow you to obtain readings, then you will need to transom mount the transducer. You can also visit installation pictures section to view how others have done it.  http://norcrossmarine.zendesk.com/forums/20383626-installation-pictures