You might be able to get a crossover cable from transducer maker Airmar. I have a bunch of these I use for electronics testing. My test boat has an Airmar thru-hull transducer glassed in flush. It terminates with a 10-pin Furuno connector. I have hooked this transducer to at least 25 different sounders over the last 5 years of testing. It works everytime as long as I have the right crossover cable.
Al
Marine Electronics Reviews and Installations Tips