Adam,
Agreed that the 4 strokes are quieter than the new generation 2 strokes, however, they are no more economical. In fact I am getting far better fuel economy with my E-Tec than I ever achieved with the Honda.
Have never used more than 25 litres on a fishing trip yet and averaging around 1.5 to 1.75 NM per litre.
I echo PD's comments. 2 Strokes are more economical in most of the rev range. Comparative tests on 75 and 90 hp found 4 stroke is more economical at id ringe only.