The March edition of Practical Sailor has a run down on all the 4-stroke outboards.

". . . the price of small 4-strokes has dropped within reasonable range of same-power 2-strokes. (The same is not yet true of the bigger four-strokes, unfortunately.) The bad news is that weight remains a major issue with the small 4-stroke outboard. Some are so heavy they don't qualify as "portable" engines, in our view."

For example, the 6-hp Suzuki, Tohatsu, Nissan and Mercury all weigh 55 lbs. with a 15" shaft, a bit more with a 20" shaft. The 6-hp Johnson is about 13 lbs. heavier at 68 lbs, but the Yamaha is really heavy at 83 lbs! [As an 8, the Yamaha is one of the lightest engines along with the Johnson 8.]