I start the day by establishing some baseline numbers for our project craft, a waterbike that in its stock form will thrill even the most jaded speed freak. On this relatively calm, 72-degree Florida morning, the RXP proves strong, setting a 69.14-mph baseline. It also impresses me with its 1.72-second acceleration from 0 to 30 mph. A $100,000 offshore go-fast could take up to 12 seconds to do the same.
It's this rocket-like acceleration that instantly separates a waterbike from most speedboats. Only inches removed from the water and straddling a craft that's barely 4' wide, I experience a rush of speed I've never felt inside a cockpit. It's an arm-wrenching, sphincter-puckering surge that happens so quickly, it takes a few seconds for my brain to catch up. It's so sudden that without the proper stance, the rush forward could be hard to control. Before launching, I have to stand with my feet braced firmly in the craft's footwells and lean most of my body over the handlebars. This helps keep the bow planted as the craft pulls hard. Otherwise, it would simply leap out of the hole and leave me in its wake. Once on plane, I ease back into a crouch, in contact with the seat but with most of my weight supported by my legs. At top end, the speed pulls tears from my eyes and flaps my cheeks as if I were in a hurricane.
Impressive? Sure. But I'm looking to hand a go-fast its lunch. So it's time to get dirty.
Back on land, the switch to Riva's Stage I components goes relatively smoothly. The primary challenge is wrestling the lengthy stock intake ducting out of the waterbike's snug engine compartment. It's easier if you remove the engine compartment cowling - just make sure to tape the exposed fiberglass edges or you'll get some nasty cuts.
It's a cumbersome job, but by removing the stock piece in sections, I get it done, albeit with the help of a few four-letter words. Part of the stock unit I pull out through the bow's stowage hatch. The remainder I ease out via the engine compartment. Installing Riva's replacement part is far easier. I slide in this shorter piece using a sweeping motion, then fasten the ends in place, one at the supercharger, the other at the front of the engine. Riva's instructions are clear and detailed, but there's tech support available by phone if you need it.
The remaining parts require removing the pump and switching out the stock impeller. Everything else is accomplished with basic hand tools, but the impeller requires a special $31 tool from Sea-Doo. The pump wedge is installed as I reassemble the pump. A swap out of the stock intake grate, a little silicone sealant, and I'm done. Time on the clock: 4 hours, 5 minutes. According to Bamdas, Riva techs would do the work for me in three hours for about $300, plus another hour of labor for water testing. I think most moderately skilled owners could easily handle the job.
BURDEN OF PROOF
Back on the water, I reacquaint myself with the newly kitted RXP. From a pure seat-of-the-pants perspective, the performance gains are felt mostly on the top end. To verify this I set up for a radar run. I idle into position, then punch the throttle, summoning all of the RXP's power as I rocket across the lake on a series of back-to-back runs. A check of the computer confirms my intuition. I hit an average top speed of 71.9 mph, nearly a 3-mph gain, yet only slightly improved on the stocker's already strong acceleration, going from 0 to 30 mph in 1.65 seconds, a gain of o.o7 seconds.
Had that hypothetical go-fast been next to me at the start I would have handily beaten it off the line, then slowly increased my lead as we sped across the lake. I'm impressed.
Purely for grins, I meet up with the Riva techs at the company's test lake and take the throttle behind two of the company's higher-end packages - one with a Stage II kit, the other tweaked to kill with a Stage III. These modifications aren't as simple to install as my Stage I, although they're still relatively inexpensive. However, Riva doesn't recommend them for recreational use, billing them for "competition" only. You also need to be a fair mechanic to do the installations.
The Stage II kit costs around $2,900. It contains the workings of the Stage I package and adds such items as a new supercharger impeller and oversize intercooler. Riva's Power Cooler claims to deliver a 15-hp increase in peak power, while lowering exit temperatures an average of 50 degrees. Cooler air equals better power, and this is the big-ticket item on the list, costing nearly $1,300. Other mods include a rear exhaust kit, which reduces backpressure and restriction in the exhaust but does away with the stock sound suppression system. Performance types might love the throaty growl, but your neighbors will likely feel otherwise. Still, it's a lot quieter than the average go-fast running an open exhaust. Other components affect handling, including the removal of the stock off-throttle steering system as well as the addition of performance sponsons.