Re: used pontoon boat/party boat
You might want to find a pontoon boat that has the largest engine allowable by the manufacturer. With 25" pontoons, most would put a 90 hp on a 20' pontoon, a 115 hp on a 22 ft and a 150 hp on a 24' pontoon. You could ski with any of them. My 24' (115 hp) pontoon will pull skiers, however I'm really not comfortable in tight turns. A full hulled boat just does that job so much better than a two toon boat.
If money wasn't an issue, the best performers are tri-toons--especially with lifting strakes, commonly called high performance pontoons. They're best when used by 150 hp motors or larger, and they give incredible speed, handling and pulling ability for a skier. That's really the way to go, but the price is relatively high--even used.
Good luck!