Sea-Doo has reopened personal watercraft's longest-running horsepower fight. The 2027 Rotax 1630 ACE now makes 350hp, the most powerful factory PWC engine in production, and cuts the RXP-X's 0-60mph sprint to a claimed 3.1 seconds.
The 350hp engine appears across four models: the RXP-X 350, RXT-X 350 and GTX Limited 350, plus the new RXP-X Senna 350.
What changed
The supercharger compressor wheel grows from 72.5mm to 75.5mm, moving more air into the 1630cc three-cylinder engine, and the rev limit rises from 8,250rpm to 8,500rpm. Sea-Doo has strengthened the connecting rod and its bolts to handle the added load, alongside a redesigned intake grate, revised stator vanes and a reshaped ride plate aimed at reducing cavitation and improving pump hookup. Sea-Doo claims a 0-60mph time of 3.1 seconds for the RXP-X 350, down from 3.4 seconds on the outgoing 325hp version.
The climb to 350hp
The Rotax 1630 ACE launched at 300hp in 2016. It climbed to 325hp for the 2024 model year, giving Sea-Doo the highest claimed factory horsepower among the major production PWC brands, ahead of Kawasaki's Ultra 310. Now, 350hp extends that advantage further.
| Model / Year | Engine | Peak Power | 0-60mph (5-60mph tested) |
|---|---|---|---|
| Sea-Doo RXP-X (2016) | Rotax 1630 ACE, supercharged | 300hp | n/a |
| Sea-Doo RXP-X (2021 test) | Rotax 1630 ACE, supercharged | 300hp | 3.60 sec (independently tested) |
| Yamaha GP1800R SVHO (2021 test) | 1.8L supercharged SVHO | 250hp | 3.85 sec (independently tested) |
| Sea-Doo RXP-X (2027) | Rotax 1630 ACE, supercharged | 350hp | 3.1 sec (Sea-Doo claimed) |
| Kawasaki Ultra 310 | Supercharged 4-stroke | 310hp | n/a |
All current-generation stock PWC models sold under US specification share a voluntary top-speed limiter of roughly 65 to 70mph, regardless of horsepower.
Where the numbers stop mattering, at least in the US
A 100hp gap between Sea-Doo and Yamaha's GP SVHO sounds decisive until the speed limiter enters the picture. US market PWCs have long operated under a voluntary industry speed restraint, introduced at the request of the US Coast Guard rather than as a formal regulation, and today's fastest US-spec stock machines generally top out in the upper 60mph range regardless of horsepower. Acceleration and handling carry the real competition instead. A controlled side-by-side test in 2021 clocked a 300hp Sea-Doo RXP-X at 3.60 seconds from 5-60mph against 3.85 seconds for a 250hp Yamaha GP1800R SVHO, a quarter-second gap despite a 50hp difference, helped by the Yamaha's lighter NanoXcel2 hull.
Australia gets a different proposition. Sea-Doo sells higher-speed RS specification performance models there, and the outgoing 325hp RXP-X RS has been instrument-tested at around 118km/h, with individual runs closer to 120km/h, well above the US-spec limiter. Whether New Zealand receives the same RS specification as Australia, or the US-limited version, hasn't been independently confirmed, so it's worth checking with the local distributor before assuming Kiwi buyers get the extra speed.
The trade-off
The GTX Limited 350 loses Sea-Doo's Intelligent Debris Free system, or iDF, which lets the rider reverse pump flow to clear weeds and debris from the intake without getting into the water. Riders working weed-choked water will feel that one.
The flagship wears the same engine
The RXP-X Senna 350 comes from a one-year partnership with Senna Brand, a global company created by the Senna family to perpetuate Ayrton Senna's legacy, and is limited to 1,991 units worldwide, each carrying a numbered plate reading "1 of 1991" rather than an individual serial number. Under the paint job and the price tag sits the identical 350hp engine found in the standard RXP-X.
