You will probably be amazed at the similarities. Outboard performance and economy "tain't what it used to be". With loop charging for carburetored engines; injection for that type, with exhaust tuning and streamlining of the lower unit and great props and all with PTT, plus pound per hp lower weight 2 strokers of this era really can give 4 strokers a run for their money. If you are worried about fuel all that much, go to the OEM charts on boat performance and look at the curves. You'll find that your best economy is just on plane, not blasting away at WOT. While on the charts look at your WOT fuel consumption handicap. If offshore you aren't usually going to be going all that fast anyway. Other thing is that the whole OB is corrosion protected whereas a lot of the Inboard type aren't. I have had both and won't go back to inboard engine propulsion and on outboard it will be 2 stroke.
I know nothing about the Etech but were I in the market for a new rig and all I certainly would spend time learning about them. Some time ago, 6 mo. or so, I saw a documentary on the Etech factory and it was very impressive. One thing that caught my attention is their usage of 0.0001" rather than the normal 0.001" tolerancing which is usually the norm. Just one example of the effort that goes into those engines. Possibly you can pick up the video on You Tube.
