We tested the 21 SSi with the 240 hp Volvo Penta SX drive, and achieved a top speed of about 47 mph and snapped onto plane in under 4 seconds. The power steering and super-smooth throttle and shift enhanced the sporty feel of the responsive hull. If you are into sterndrives, and most inland boaters are, the 240 was the ideal horsepower. However, Chaparral also offers the 21 SSi in an outboard configuration. We tested that one with a 200 hp Yamaha and brought it onto plane quickly, reaching a top speed of 45 mph. In both models, the boat crushed doubled-up wakes without rattling hatches or teeth. Turns were graceful, and only the most aggressive turns caused a little slippage.