It "should" work with etecs, they are backward compatible with older style instruments. Up to a couple of years ago, etecs were still supplied with the old style gauges in the States, I-command was an optional extra.
I'm not sure if that is a genuine BRP/Evinrude gauge though, it could be an after market. In which case ignore my first comment.
Rule#2: Never argue with an idiot. He'll drag you down to his level & then beat you with experience.
Rule#3: Tha' can't educate pork.
Rule#4: See rule#5