I have a Sea Nymph and rate it a very sea-worthy boat, not a fast boat due to the displacement hull design, about 7/8 knots will be your maximum speed, and a 20 hp is more than enough to achieve this. I have a Mercury 25 hp and only ever run at 1/3 throttle, due to the engine well design once you have arrived at 7/8 knots the more power you deliver to the boat only results in the stern getting lower in the water, due to the engine being a couple of feet forward of a traditional transom and the fact that it is not a planing hull, that said, I don't believe you could be in a safer boat for its size, I hope this helps and will be happy to answer any other questions, regards Steve.