Jet Drive vs Sterndrive Pt. 1 of 6

Jet Drive vs Sterndrive

Muscling their way onto the market in the early ’90s, “sport jets” were dismissed as little more than toys, quick and agile playthings, scoffed at by serious boaters. They peaked quickly and then vanished just as fast.

But a funny thing happened on the way to obscurity. Sea-Doo and Yamaha developed bigger, more versatile offerings. Today jet-powered runabouts are the best-selling models in the 24- and 21-foot segments.

To find out why jets are giving sterndrives a run for their money, and to determine if jets are suitable propulsion for experienced boaters, we pitted a Sea-Doo 210 Challenger S featuring a single 255 hp supercharged high-output Rotax jet drive against a Chaparral H2O 19 Sport with a 220 hp MerCruiser sterndrive and put them through their paces.

Round 1: Layout
Dock a sterndrive boat and its jet-drive counterpart side by side and the difference is obvious. A sterndrive engine, based on an automotive block, is much heavier and larger. MerCruiser’s 4.3 MPI measures 28 by 30 by 22 inches and tips the scale at 775 pounds without the Alpha sterndrive. By comparison, Sea-Doo’s Rotax is 30 by 21 by 18½ inches and weighs 198 pounds. The sterndrive’s drive shaft exits the hull and then makes two 90-degree turns before linking to the propeller. The drive itself adds 85 pounds to the total. The Sea-Doo drive shaft links directly to the impeller, housed within an enclosed jet pump with integral pivoting nozzle, adding 35 pounds.

The jet’s smaller profile enables boat designers to take liberties unavailable with sterndrives. Most notably, jet boats aren’t forced into a sun pad layout in order to enclose the engine. As aboard the Sea-Doo, this opens up the aft cockpit with low-profile benches and center transom walk-throughs. In contrast, the Chaparral features a sterndrive’s typical sun pad, nice for a passenger wanting to lay out but cumbersome to climb over when boarding. Many sterndrive manufacturers combat this with walk-through passages to the side of the engine, but ultimately a sterndrive takes up a bigger percentage of the boat’s volume.

Layout and boarding ease aside, it’s interesting to note that the shorter, narrower Chaparral (20 feet 6 inches by 7 feet 6 inches) and the longer, beamier Sea-Doo offer almost identical passenger space forward of their platforms. I measured the Sea-Doo as having a 42-inch-long bow cockpit and 90-inch-long main cockpit and the Chaparral a 45-inch-long bow cockpit and 90-inch main cockpit. The big differences are aft of the cockpit. The jet engine’s small size grants Sea-Doo a three-foot-long swim platform, with padded backrests for seating when not under way, and a large stowage locker built into the platform. By contrast, Chaparral takes up nearly the same three feet in sun pad length, followed by a smaller, 20-inch-long platform.

Part 1 of 6