"Depth finder transducers use
"Depth finder transducers use sound waves through water to locate the sea floor (and fish). Generally they radiate a cone of sound through the water in a vertical axis - i.e. straight down. More expensive ones radiate several cones in an arc, but the principles are the same.
As long as the transducer is in the water when you are using it, and it is fitted in the orientation shown in your installation manual,it will work fine.
The optimum place is on the keel, but outboard engines and trailering can damage them, and inboard powered craft can generate cavitation or air bubbles which will seriously affect its use when moving. That is why your manual says to mount it halfway between the side and the keel, to have it in the water, but to get it away from air bubbles.
As your using a small tinny your going to get air under the hull when going at speed anyway so don't expect to have a useable sonar picture. Slow trolling and sitting still you should have a good picture AS LONG AS THE TRANSDUCER IS IN THE WATER.
Mortens way of mounting is good for metal hulls though I would expect a little attenuation of signal though this shouldn't affect the recreational fishing boating people too much, but I have my reservations about fitting an external transducer internally on GRP/wooden hulled boats. If you do epoxy it to the inside of the boat it is vital you get rid of all the air bubbles (you may have gathered air is bad for a sonar picture).
Mine is mounted at the same horizontal level as the top of the lower unit outside the boat on the transom about halfway between the keel and the side of the hull (and I dont get a useable picture above 10 knots in flat calm conditions due to air getting under the hull)."
