I assume you have a Fusion
catamaran?? You may find
posting in the Multihulls section more profitable??
Over 20 years ago we were building the 35ft Banshee sailing
catamaran. An 8 berth performance cruiser with bridgedeck
cabin so probably something like a smaller Fusion in
concept.
One US customer fitted twin 90hp outboards. I
motor sailed it at 16 knots, and sailed it at 19. I have a
photo showing him towing a waterskier at 22 knots (with the rig up).
However the
fuel consumption was pretty horrible. At speeds over 10 knots you will need roughly another 10hp for every one
knot speed increase.
So how fast do you want to go?? Do you want to do 2mpg or 10?
I would say that 8 knots was a sensible maximum
Richard Woods of Woods Designs
www.sailingcatamarans.com