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Runabout GP1

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Runabout GP1

UIM2026, 502.04. An open class. It carries no clause requiring the craft to stay stock, so anything the rules do not restrict appears to be permitted. That reading is ours rather than the rulebook’s.

Open questions on this class (4)

Places where the rulebook contradicts itself, or where a figure could not be settled. Nothing in this list is decided, and it sits here rather than in a footnote because it is what you would want before spending money.

  • No boost pressure limit is published - the single largest gap.
  • No ECU rule, no ignition rule, no driveline rule, no intercooler rule, no steering or handlebar rule.
  • Whether the lower classes' handlebar padding requirement applies to GP1 is not stated.
  • The appendix diagram for the pump cover plate referenced at 502.04.02-04 was not located.

Sections this rulebook does not contain for this class

Confirmed absent by a targeted read rather than merely unnoticed. In a closed-list class an absent article is why a part reads as not permitted; in an open class it is why one reads as open.

  • engine block and crank
  • cylinder head and camshafts
  • porting
  • fuel injection and throttle body
  • ignition and ECU
  • jet pump and impeller and nozzle
  • steering
  • handlebars
  • hood and hatches

What the rules say (68 parts)

18 permitted outright, 48 answered by our reading of the class rather than by a quoted rule, 50 the rules do not settle. Grouped by the answer, because an open class gives one answer to most questions and printing it once per part would say the same sentence forty times.

No rule, this is an open classOur reading, not a rule we can quote at you. This class carries no stock clause at all, so anything unlisted appears to be open. The rulebook does not say so in terms.

Legal, within limits1 part

Must fit the OEM battery box and be securely fastened. GP2 additionally allows relocation of the battery, box or housing limited to the strict minimum needed to fit an aftermarket exhaust.

Legal, within limits1 part

BOTH turbocharging and supercharging on four-strokes, capped at 2000 cc. Water-jacketed housing and manifold required. NO BOOST LIMIT IS PUBLISHED. 502.04.01-01c, 502.04-07

Legal, within limits1 part

Max 100 mm beyond THE END OF THE PUMP ITSELF - a different measurement from the lower classes' 177.80 mm plate dimension. 502.04.02-04

Legal, within limits1 part

Full-length type with at least one bar parallel to the drive shaft, all leading edges radiused, extending no more than 12.00 mm below the flat plane of the pump intake area. GP1 adds that the projecting member must be filed so as not to create a hazard.

Legal, within limits1 part

Identical, plus the bond-flange protrusion clause. 502.04.02-02

Legal, within limits1 part

Prototypes expressly permitted via the UIM logbook. The 50-specimen threshold does not apply. 500.02.02, 502.04-08

Legal, within limits1 part

Aftermarket, modified or PROTOTYPE seats permitted. Must respect the structure and measurements of those available on the market for pleasure-navigation homologated PWC. The base must be well consolidated as it is the divider between the engine compartment and the seat. Seat height may be modified up to 10% from the original model. Back rest height max 18 cm with rider seated. 502.04.03

Legal, within limits1 part

Replacement bumpers allowed. A soft flexible water-spray deflector may attach to the hull sides or bond flange, not exceeding the perimeter of the original bumpers or the external hull edge measured with a plumb line. SAFETY BUMPERS ARE COMPULSORY in both GP1 classes.

Legal, within limits1 part

Same. Ballast may be added prior to competition to meet the 300 kg minimum. 502.04.02-07

Legal, within limits1 part

All cooling system valves must be of FIXED OR AUTOMATIC type - thermostats, pressure regulators, solenoids. Manually controlled devices that alter cooling water flow while under way are prohibited in every class, as are electronic water injection systems unless of origin.

Legal1 part

Padding and mat kits may be added and custom painting is allowed. Metal components above the bond flange may be polished, shot peened or painted.

No rule, this is an open class34 parts

No article covering this part. Free under the open-list reading of GP1.

No rule, this is an open class1 part

Not specified; free under the open-list reading.

No rule, this is an open class1 part

No hood article.

UIM 2026, 502.04, read from the rulebook on 2026-09-08, not verified by a racer. Read the rule yourself. Every UIM class · where the rulebooks differ.

This is one class. Every part below also has a page of its own showing where it stands across every class this body runs, and legality by part is the index of them.

68 parts read · 18 permitted outright · 2026 rulebook

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