I don't have any particular knowledge of the recommended SONAR transducer transom mounting location for a 240 OUTRAGE, but the general scheme for mounting a transom-mount SONAR transducer is given in an article in the REFERENCE section at:
SONAR Transducershttp://continuouswave.com/whaler/refere ... ducer.html
For single engine boats with a right-hand propeller the usually recommended location is on the Port side of the transom. See the section of the article under the sub-headings TRANSOM MOUNTING LOCATION and SINGLE ENGINE for more details.
The usual problems causing loss of bottom echo when the boat is underway at speed are:
--turbulent water coming off the hull due to a running strake being upstream of the transducer, or
--improper depth of immersion of the operating surface of the transducer into the water; this usually is insufficient immersion, but problems can be created by too much immersion in which the transducer body creates the turbulence itself.
Most SONAR transducers designed for transom mounting will have a mechanism in the mount that will permit some up-down adjustment of the depth of immersion of the transducer.
The real knack for installing the transducer is getting the holes in the transom in the right vertical position, which will permit a range of adjustment of the immersion that will produce the proper location of the transducer working face in the water stream. Usually the manufacturer of the SONAR transducer will provide details about the mounting height.
With a V-hull boat such as an OUTRAGE, the distance off keel centerline is another factor. When the boat transitions to plane the hull will lift. If the transducer is too far off keel centerline, when the boat is on plane the transducer will be running in airy water. Checking the transom while the boat is on plane and observing where the waterline is located can be helpful in knowing how far off centerline the transducer can be mounted. Generally you want it far enough off-center so there is no possible mechanical interference with the engine gear case when the wheel is hard over in the direction of the side of the transom the transducer is located.
If the Port-side mounting is not particularly convenient due to concern about cable path or other interferences, then a Starboard-side mounting will work, too. The SONAR transducer on my boat is mounted on Starboard and works very well.
Keeping the SONAR transducer cable away from other electrical and electronic cables is important. Take care in routing the cable to minimize the chances for other cables to leak interference into the SONAR cable.