This thread has been dormant for a while. Hope nobody minds me churning it up.
I just bought the 640 and have a couple of questions/comments. I called Garmin tech support, but the tech who helped me didn't know what VMG means.
It appears that the 640 will not display VMG to a waypoint unless you have a wind instrument connected. This doesn't make any sense, and I hope I'm wrong. I had a 478 (and many previous Garmin chartplotters) that did this, and I'm totally confused as to why they would omit this. It's a trivial calculation. The Garmin support person told me that VMG was actually removed from the 478, and I'd have lost it if I'd done a software update.
Second, the optional bar across the screen that shows data from a wind instrument is cool, but Garmin doesn't seem to sell a NMEA 0183 wind instrument. Could anyone recommend a headless instrument or a converter from NMEA 2000 to 0183?
Other than the VMG gripe, this thing is really cool. I'm considering the flush mount, but it's hard to cut a hole that big in the bulkhead!
"Figment" 1978 Pearson 30 #1083