I don't think there is a written spec, a few inches of airspace is what they recommend. If you are mounting it vertically it will shed heat a little faster.
You are over thinking it. The prop is behind the transducer anyway, but if you can stay 20" away from it I think you won't have any problems. If you are unsure post a picture of your transom and I'll let you know.
Sorry I meant Woody not creekwood, too much wood around here. Your observation about right of way is dead on. It's just a coincidence. The difference between course and heading will be significant if the effects of set and drift are significant. If they are not the difference won't be much. The...
I don't think you have a source for heading info. The Rn300 GPS is a source for position info, and course info from that. Heading requires a heading sensor.
No there isn't. The sizes are considerably different now, and the newest raymarine Axiom MFD's do not have an easy way to hook to the older Sea talk 1 accessories. Sorry.
Kevin if you already have the Garmin cable end and just need to go to Ray end you just cut it off and splice it. I'll get you a part number. If it's a new install, Chris and I both recommend the mix and match and raymarine end. I'm sure there was an error in translation.