Re: Raytheon L365 depth-o-meter advice
They are often interchangeable. The key is to figure out the wiring of the current transducer and it's frequency (200khz is the most common). The transducer is most likely made by Airmar and they have wiring diagrams for most of them. I'm playing with this now on my Pearson trying to get my MFD to talk to an older transducer.
However if it isn't interchangeable that isn't a big deal. For a solid fiberglass boat you can mount a depth transducer inside the hull as long as you get no air between the bottom of the transducer and the fiberglass (and the fiberglass that you use has no voids). You will loose a little bit of sensitivity this way, but it is probably the difference between measuring 400' deep and 600' deep. That is my backup plan if I can't use my existing transducer.
Toilet wax rings work well as the mounting substrate.
1986 Pearson 28-2 "Elena"
frequent crew/prior owner on Catalina 25 "Lutra"
Shilshole Marina, Seattle, Puget Sound, WA, USA