90 ETEC on a Potter 20 CC???

[bitsamonkey]

I know you can do it and be happy with the results. I run a new generation Suzuki 90 25" on the transom of an 18'. I can cruise at 28 mph and top out at 38 mph light. More weight drops cruise to around 24 mph. I get up to 7 mpg at cruise and the boat is very responsive, gets on plane quickly, and stays there down to about 13 mph. I would never go back to a heavier motor on these hulls. The way this boat rides with a light engine on the notch is infinitely better than with more power and more weight.
Look at the Suzuki 90 and compare performance reports of similar or equal hulls. I studied all of this info for weeks before committing to the Suzuki. It's a tad heavier, but pushed the same hulls faster with less fuel. It also has a higher final drive ratio which allows you to use a bigger prop. I run a stainless 14x18 3 blade with a cup.
I think there's something to be said for rigging small boats light with lower power. A friend just put a 40 hp tiller 4-stroke on an old aquasport 17 and cruises between 20 and 25 mph tops 29 mph. Here in Miami you're not going any faster in these small boats anyway.