Formula 800

Quoted from Group K's page. Not measured here, and not reproducible without knowing the conditions, which are mostly not published.

Top speed

52 to 53 mph at 7,250 to 7,300 RPM Group K's figure for its own package. Nobody here has measured it, and the page does not state the water, the rider weight or the hull condition it was run on. Their stated stock baseline for comparison is 43 to 44 mph at 6,350 RPM.

Displacement after big-bore

753cc at 84mm bore From 701cc at 81mm stock. Group K says the stock sleeve tops out near 84.5mm, so the package deliberately stops at 84mm to leave room for a later overbore.

Fuel and mix

91 octane minimum, 32:1 pre-mix Group K's requirement for this package, against a stock spec they give as 87 octane and 50:1. Read it as part of the build rather than as a preference.

A tuner's package rather than one person's race ski, and the parts list is Group K's catalogue, so read it the same way as the RIVA entries here. Its value is that it is a complete recipe with the reasoning attached, which is rare: it says why the single 44mm carburettor is chosen over twin 38s for low-range pull, why the heavier 64U head casting has to come with the big-bore rather than after it, and why stainless reed petals are refused at raised RPM. Two of its cautions are worth more than the speed figure. Group K says running the tank low in rough water lets air into the fuel system and detonation follows almost immediately, and that the stock 7,050 RPM limiter has to be raised or the package cannot reach the powerband it is built around. The ride plate choice is presented as a trade rather than an upgrade, costing smooth-water speed and making the ski steer on the nose. Check any ride plate extension against the class page for the class you enter before fitting one, because this page is the builder's view and not a rulebook reading.

Whether any of it is legal in your class. A builder describing its own product, including by a class name, is not a check against a rulebook. Class legality holds the checks that name a section and a person.

Whether it would do the same on your machine. A quoted top speed is one builder's result on one craft, usually without the conditions, the rider weight or the fuel.