The power of the 1.5-liter Rotax triple startled me when I first hopped on board the RXT-X. After idling through a short no-wake, I grabbed a finger-full of throttle and was almost pitched off the back of the seat. This new version of the Rotax mill used in almost every Sea-Doo model has been tweaked up from 215 hp to 255 hp with 25 percent more supercharger boost, a larger intercooler, high-flow fuel injectors and forged pistons. Premium unleaded is mandatory. Closed cooling remains a standard feature (the heat exchanger is built into the ride plate), which is especially handy if you ride in salt water, but also allows the engine temperature to be more precisely controlled.