The Kawasaki Ultra 150 boasts one of the most technologically advanced engines in the industry, which Kawasaki conservatively rates at 145 horsepower. It features three separate lightweight aluminum cylinders, which are connected only at the crankcase. Each has its own cooling water jacket to ensure that cooling capacity matches the high power output. On the inside of each cylinder is a lightweight, wear-resistant Nikasil plating for maximum heat dissipation. New counter balancers at both ends of the crankshaft make this the smoothest-running Kawasaki triple ever produced, and it's also rubber-mounted in the hull for a more comfortable, vibration-free ride.

The engine is fed by triple 40mm constant-velocity carburetors. Each carburetor is linked to the digital DC Capacitor Discharge Ignition system by the Kawasaki Throttle Responsive Ignition Control throttle-position sensor. The entire system alters the independent timing maps for each cylinder based on engine speed and throttle opening for quick throttle response and acceleration. To reduce power fade if air temperatures inside the hull rise, such as when riding on a hot day, a sensor in the CDI advances ignition timing to enhance the engine's response. Engine temperature is constantly monitored by a sensor located at the exhaust pipe, and if the heat rises to 90 degrees Celcius or above, the ignition gradually cuts engine speed to 3500 rpm where it stays until the temperature is lowered.

For maximum engine performance, the Ultra 150 uses a dry exhaust. Water jackets encase the exhaust pipe and exhaust manifold, allowing exhaust gases to flow completely dry and free from power-robbing water vapor. This water insulation also suppresses engine noise and lowers the temperature of the aluminum exhaust components for increased durability.