The problem is NOx emissions, if I remember right, hard to manage with 2-strokes although techniques like variable exhaust port heights (varying effective compression ratio) help, and work is ongoing.

Marine engines are subject to much laxer emission controls than highway engines. It is not possible to run a two stroke in closed loop in conjunction with a 3 way catalytic converter-which rules out its use in petrol engines.

The critical acclaim is mainly from the companies' press offices!

Diesel engines?

The only company making high speed two strokes is Detroit Deisel-and they've spent twenty years desperately trying to get out of the two-stroke business. They know more about two strokes than anyone else-and the fact that they're not interested should tell you something...

Detroits were horrendously noisy, had a narrow rev range, slobbered oil and had worse emissions than a four stroke. The kicker was that weren't as fuel efficient as 4 strokes either. Absolutely no reason to revisit the concept.

Once turbocharging and high pressure injection allowed 4 strokes to reach the same power levels as two strokes-the detroit was dead.

The 2 stroke has one major advantage: because it fires twice as frequently as a 4 stroke, the torque delivery is smoother and it imposes less stress on the clutch and drivetrain. But the list of negatives is just too long.

Evinrude have had and are still having major problems with their engines and was a major factor in causing them to go bust the last time before Bombardier took them over-they are so finicky that the spark plugs have to be indexed -ie the earth electrode has to face a certain way in the combustion chamber-there is no earthly reason why anyone should buy an engine of this type-if you want a decent outboard, buy a Honda or Suzuki four stroke.