My 1969 Chrysler 20 HP comes with a 14:21 gear ratio and an 8 1/2 " X 8 1/2" propeller, the 1981 model has a 2:1 gear ratio and an 8 1/2" X 10". If the 2:1 is a reduction ratio, at WOT the 1981 motor will rev. at half the motor speed. But in my case my motor will over rev. the propeller because it is a multiplication gear. What prompted this change in phylosophy? What are the consequences in terms of fuel efficiency and motor durability?<br /><br />Thanks in advance for shedding some light in this matter that intrigues me.