on a 5 metre or close aluminium runabout which would be the best option, 1st an 08 model low hour (approx 120 from memory) 60 Yamaha four stroke, 2nd an 05 model 237 hour Mercury 75 four stroke and lastly an 04 model 155 hour Mercury 90 2 stroke. My head says go with either of the four strokes for quieter running with better economy, but the head is thinking of the fun of the 90.