Though technically a new engine for Sea-Doo, the 1630 is loosely based on the previous Rotax 1503. It features the identical 100 mm cylinder bore, but gains 9 percent in displacement due to the stroke being lengthened from the previous 63.4 mm to the current 69.2. Cylinders feature a new plasma coating, rather than pressed-in, iron sleeves. Applied by a proprietary thermal spraying process, the coating minimizes friction, improves heat transfer, and reduces engine weight. Pistons have been redesigned with longer, coated skirts and weigh 20 grams less. Connecting rods, shortened to accommodate the increased stroke, are also lighter. Additional changes include the improved shape of the single overhead cam cylinder head, larger injectors, and a coil-on-plug ignition system that delivers nearly twice the discharge.