Bavaria 36 cruiser Transducers 1995

[Binkyburdett]

Hi, I’m updating my Raymarine tridata system to an NMEA2000 based system with a new ST810 triducer. I’d like to keep the existing transducers and ST60 as a backup. Three questions:
1) Firstly why has my boat Bavaria 35 Holiday/Bavaria 36 cruiser (more or less the same) got three factory fitted transducers? One is clearly the speed, the depth has also been identified but what is the third, it appears to be an additional depth transducer as the cable has three wires black/blue/grey as per the known depth transducer (in photo speed transducer removed and blank inserted)
2) all three transducers are very close proximity to each other, about 6” apart. Is this going to be an issue if the triducer is inserted where the third transducer is currently located?
3) does anyone know airmar model of speed transducer fitted to Bavaria’s at the time as the paddle wheel is kaput

Many thanks in advance for an info, James