Specifically looking at the 740.

Dave

I have the 740s. I read that it is, although my engines are carbs so I have no personal experience.

if the smartcraft is NMEA compatible then probably yes

Yes, thru nema 2000. But you will need a gateway from mercury, ($350.00) two cables and a port expander .

Also will need a backbone for the nmea2000. You cannot plug the gateway into the back of the 740 directly. Both the 740 and gateway go to the backbone along with two terminators and pwr 12vdc. If you Garmin with external antenna and backbone you only need a tee

Smartcraft is a proprietary Mercury communications protocol and, as such, will not communicate with ANY NMEA2000 chartplotter without a gateway. (Thanks, Mercury...)

On the positive side, I have a 740 and really like it. Since I am Ilmor-powered, there are no communication issues.