That somewhat sad and neglected Gemini catamaran is a great example of the more is better silliness where engines and horsepower come into play...
Really, eighty horsepower?
The Gemini is a light boat (some might even say TOO light) and it does not take a lot of power to make it get up and go. Its rig HP is something close to 6.3 HP @ 10 knots of wind, 8.5 HP @ 14 knots of wind, and 17 HP @ 20 knots of wind. Which pretty much says to me that anywhere between a single 8 HP and a 25 HP outboard would be OK and my engine of choice would more than likely be a 9.9HP because the Gemini has a fair amount of windage otherwise I'd have gone with the 8HP.
Then again, eighty-fucking-horsepower...
Offhand, I just can't see why anyone would want an engine that exceeds their rig's horsepower unless what they really wanted was a power boat. If so, why even bother to carry around an expensive rig?
For those keen on checking their rig's HP, the formula is HP at 10 knots
of wind = .015 X square feet (use .020 for 14 knots and .040 for 20
knots). Not perfect but it is accurate enough to tell you what you need