Where could I find one? Just any auto parts store?
It's not OBD-II, it's marine specific. As AD said, Rinda is the only company authorized to distribute scanner software, and scanners (for Mercruiser).
You can get the top of the line, the Diacom software. Load it up on a laptop, plug it in via USB and you have realtime display and interaction with the ECU.
A stand-alone scanner (TechMate Pro) that also has some realtime feedback.
Then you can get the Codereader. Very basic, and no information about the output of each sensor...
Honestly, for the extra $200, I'd buy the Diacom over the scanner, and the codereader is by far the least useful (but still better than nothing)..
Chris.........
EDIT: Having just re-read the Rinda site (and found a new toy, eh tool, to buy ) the Codereader is for MEFI1 to 4 only, not any of the ECM/PCM controllers. You have a choice of either the TechMate Pro or the Diacom software. I have the software. Expensive, yes, very, but after you use it twice, it's paid for itself... And you can scanner all you friend's engines too. (and charge them )