Hi Roger, I bought a Lowrance hd 5 and have been very pleased. The reason for purchasing it was it's NMEA 2000 compatability, in case I ever can find a engine sending unit for our 318's all interfaces can be read back at the depthfinder/gps unit. I also installed it so it can be used at either station (fly or main) by putting in an extention sender cable and a spare power lead at the flybridge. Jack

The first thing to do when shopping for a depth finder is to spend some time on the Airmar website because they make most of the depth transducers for the marine instrument industry. I started with ordering a likely kit and it came with a 1 7/8” diameter transducer. The hole in my hull was 2”. I had to buy another transducer that fit. I ended up with a nice 2” flush unit with a retractable element. I had to order it through the maker of the head unit. Airmar does not sell directly to retail customers. They do have a manufacturer cross reference on their website. The way instrument makers lock in customers is by varying the wire connector type. So if you want to use an existing transducer you need to identify the connector type. You also need to locate the specification label attached to the wire. If the wire has been cut you are out of luck.

I took out my old cut wire thru-hull by carefully chipping the outside plastic flange away with a small chisel. It was mounted with 5200. I used 4200.

Some new “smart transducers” use NMEA standards and feature depth, temperature, speed and even camera outputs. I chose a simple depth head unit that provided an output to an additional fly bridge gauge.

http://www.airmartechnol.../2009/about/contact.php

Thanks Jack & Yooper for the information.

Roger