Thanks, all, for the input. After reading your responses and speaking with tech support at Garmin
, Simrad, and a few dealers, I found the answers that I needed.
Basically, matching one manufacturer's transducer (or adapter) with a different manufacturer's fishfinder, might work, and it might not. So for $80 I can purchase
a new in-hull transducer with 25' cable directly from Simrad.
Their tech rep was knowledgeable and her recommendations were accurate and useful. All things considered, their price
for this item was lower or about the same than many other retailers and eBay,
Going deeper into this, the older system that I purchased ($375, Simrad NSS8, introduced around 2008) requires an add-on (Sonarhub) for some of the more sophisticated transducers such as Structure Scan and Side Scan. In any case, the basic echofinder/fishfinder that Simrad recommended will suit my needs.
So, thanks again. No doubt, I'll be back here soon looking for info on my upcoming AP installation!