There are many questions asked about the “best engine” for a particular boat. This page will provide some links to possible answers:

Electric propulsion is becoming more popular, and the affordability of our catamarans seems to encourage experimentation. See this twin electric 9m

Outboard Propellor types and test on 8m Linking the steering to the outboard 9.9 hp Yamaha fuel consumption (external link)

Twin outboards: Many people have added twin outboards in various configurations: From attempts to make an 8m plane: ...to smaller (9hp) mounted just in the hulls and retractable Summary of consumption data for Yamaha T9.9 with a 11 3/4“ x 7” prop on a 3000lb 20ft monohull (from the external link.(click image to enlarge))

I also found a note in the 2002 newsletter that said: Your readers may be interested to know that my husband & I decided to try a different prop on our 9.9HP 4-stroke Yamaha (ed note - presumably the “high thrust” version?) outboard fitted to our 8m Catalac. The outboard comes with a standard 9.25“ pitch x 11”. We changed it to a prop of 11“ x 11” and found our petrol consumption virtually halved, with no loss of top speed, or thrust (we even made steady, but slow, progress against Littlehampton's mid ebb at springs!). However, Yamaha only supply this prop in plastic and it did not take long to become damaged.