Airmar ST800/ST850 question - deadrise
looking to get an airmar ST800 or ST850 NMEA speed/temp transducer.
1) This is not a depth tranducer, however the manual states a deadrise of 22 or less. Mine is about 36-38 in pretty much the only place it can go (where the old, broken, nexus log is). Full keel, not great access anywhere else for it. I don't understand why a paddle wheel would need to be vertical, and presume its more standard language because all the depth ducers need it. Maybe speed is off slightly due to water flow, but I ain't racing.
The only place I could put it perfectly level is a special cut out where the depth is and get a DST instead, however it has a cut-out in the hull/keel so water flow is probably exceedingly turbulent for the paddle.
2) The difference between the two seems to be only what kind of existing mount it fits in to, there's no reason to choose one over the other when it's a new installation, correct?
3) It says "plastic" everywhere, and I assume it ain't marelon so bronze it is (GRP hull) unless anyone knows otherwise.