Topic: Maximum depth for transducer at the bottom of rod

[Alcyone]

Sorry if theres earlier topics about this, but i am building adjustable rod for transducer, so if necessary it could be lowered below any interference caused by boat or motor itself.

Longer rod of course amplifies rolling of the boat so what do you think what would be maximum depth that rod would have to reach? Would 50 cm below boats propeller be already free of any boatcausing interference?
My boat is rubberboat that floats very near of surface so motor causes probably almost all possible problems.

Ros will of course be adjustable on the fly so scanning from deeper will be done only if theres interesting objects and very low speed.