Well i know for a fact that, for a Merc the 2-Stroke is the way of the fossil. Mercury has stopped production of all conventional 2-stroke's but they still make Optimax. So the four strokes are the way of the future. Cleaner for the environment, quieter, better on gas, no smoke and weight wise it's about 85Lbs a 2-stroke will come in about 10-15lbs lighter. If you go to the Merc website 2-stroke's aren't even listed anymore.