1) Do you know of anybody who makes such a device?

Maretron's been threatening to ship an NMEA 2000 black box for engine
sensors. But it's still not available. Murphy's PowerView works with new
engines that already have NMEA 2000 or CANBus (probably not your, but check
with Yanmar).

2) Any generic parts that could be coaxed to do this?

None I've seen. Lowrance's EP-35 temp sensor only goes up to 176F so it's
no good for engine monitoring, but that's not what they sell it for anyway.

3) Installing an analog gauge would be a lot easier?

Easier and certainly less expensive. That and, frankly, having used an E-80
all this past season, along with NMEA 2000 networking, I find it's better to
have things like engine sensors on a different display. Either on their own
gauges, a multi-element gauge or on something like a Lowrance LMF-series
digital display. For things like engine temps and oil pressure you REALLY
want it visible without having to fiddle with displays. Most are calibrate
such that the normal operating value lays at a predictable and indicated
point on the gauge. That way to detect a problem you only have to scan the
dials looking for something that's NOT resting at the expected location. I
find the chartplotter is best left showing charts, radar or weather. Trying
to cram numeric or psuedo-analog gauges onto the display just crowds things
too much to be useful. And even if I had room for a whole other E-80 I'd
still use separate gauges for their quick-scan visibility.

-Bill Kearney