The 'old' EFI and carb two strokes are on the way out as of 2006, and cannot be sold in California now. The new direct injection 2 strokes are just at the point of refinement this year.

 Introduced a few years back as a result of the EPA regulations, the direct injection 'green' two strokes are actually a bit cleaner burning than the current 4 strokes. I don't know enough about the Mercury Project X 4 stroke motors to compare them to Mercury's Optimax outboards yet. I ran a Mercury racing 250 OptiMax last year. The 250 optiMax is the finest motor I have had the privilege to run.

The new 4 stroke motors are heavier, but far more fuel effecient than their old 2 stroke cousins. The bigger bore OptiMax outboards compare fairly closely to the 4 stroke models.The 4 strokes idle, troll, and run through the power curve very smoothly. No nasty smoke to breath, either. Some of the new generation 4 strokes will compare nicely in hole shot and high performance top end, too. Of course, the new technology costs more than the old in most cases.

I have tons of specs here, anything special you wish to know?