I faced the same dilemma a few years ago, and here is the path I took:
The SX120 transducer and the Raymarine transducers operate on different principles--the Raymarine is a three-wire Hall Effect transducer, the Datamarine SX120 is a two-wire small current
device. So you can't really use the existing transducer to drive an ST70 pod, without custom electronics
. And even if you did, you'll be unable to read the result on your S100 Knotlog. However, if you decide to throw out the Datamarine knotmeter
, you will be left with a 4" round hole that will have to be patched or covered up somehow when you install a newer, square instrument.
Assuming you are content with a SeaTalk
1 network (as opposed to SeaTalk
NG or SeaTalk NT), the following solution will work. The last Datamarine Corinthian knotmeter
, model CS100, had NMEA 0183
inputs and outputs, and works well with Raymarine's Seatalk 1 network, provided you use an NMEA
to SeaTalk adapter such as the Raymarine E85001 Interface Box. I replaced my S100 KL with a CS100 on my boat, and it interfaces very well with my SeaTalk network and my Garmin
chartplotters. I also installed a Datamarine CD400 depth
indicator and a Datamarine CW360 wind
indicator to add their functions to the network.
Datamarine is essentially out of business, but these NMEA-enabled units appear on eBay from time to time. Also, DMI Marine
, formed by former Datamarine personnel, sells Phoenix knotmeters and depth
indicators which are NMEA-enabled replacements
for the Datamarine Corinthian units.
Hope this helps--at least it's an option that I know works, and doesn't require patching holes in fiberglass