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Class Legality

UIM · runabout

Runabout GP1

UIM 2026, 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.

  • 1The rules do not say
  • 14Legal, with conditions
  • 4Legal
  • 52No rule, this is an open class

Read out of the published UIM rulebook on 2026-09-08, so confirm anything that decides a purchase. The full note is at the foot of the page.

Running the class

Displacement limit
2000cc forced-induction four-stroke, 2600cc two-stroke atmospheric and 2600cc four-stroke atmospheric (502.04.01-01). The main criteria state the capacities and the engine sections carry no allowance to bore, so the figures describe the engine as the class admits it. 502.04.01.
Minimum weight
300 kg dry.

Read from the same class section as the part answers. The rider side of the sport, tiers, ages, licences and what gets inspected, is set out across the bodies at Racing.

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 (71 parts)

4 permitted outright, 14 permitted with stated conditions, 52 left open by our reading of the class rather than by a quoted permission and 1 the rules do not settle. Grouped where the same rule gives the same answer, so two "Not legal" groups can sit side by side under different rules. An open class gives one answer to most questions, and printing it once per part would say the same sentence forty times.

What each answer below means

The rules do not say
Unanswered. The rules do not settle this, so ask the club before you rely on it.
Legal, with conditions
Keep it, but measure it: the rules permit this part only inside stated limits.
Legal
Keep it. The rules permit this part in this class.
No rule, this is an open class
Probably keep it. The class carries no stock clause at all, so anything unlisted appears to be open. The rulebook does not say so in terms, and this is our reading rather than a permission anybody wrote down.

Legal, with conditions1 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, with conditions1 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, with conditions1 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, with conditions1 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, with conditions1 part

Two rear sponsons are required, each at most 92 cm long, protruding no more than 100 mm, with a channel and a drop below the hull intersection of at most 63.5 mm each and a thickness over 6 mm; sponsons fixed inside the bond flange may not protrude outside it. 502.04.02-02

Legal, with conditions1 part

Permitted. May not exceed the width of the planing surface or extend more than 100 mm rearward beyond the transom. All edges radiused. No fins, rudders or skegs. 502.04.02-05

Legal, with conditions1 part

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

Legal, with conditions1 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, with conditions1 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, with conditions1 part

Ballast of constant mass may be added within the normally exposed areas of the hull before competition to reach the 300 kg minimum, with no fluid ballast and no modification or relocation of other parts. 502.04-05, 502.04.02-07

Legal, with conditions1 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 class35 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

GP4 to GP2 require the reverse gate removed, but GP1 prints no driveline article, so removal is left to the builder. 502.04

No rule, this is an open class1 part

No hood article.

No rule, this is an open class1 part

GP1 prints no article on work to the hull, so under its open-list reading a modified OEM hull is free while the craft stays within 360 cm long (394 cm for Endurance) and 127 cm wide. 502.04.01-03, 502.04.01-04, 502.04.01-05

No rule, this is an open class1 part

No article limits an extension to the hull, so under the open-list reading of GP1 one is free inside the 360 cm overall length (394 cm for Endurance), and trim tabs may reach 100 mm past the transom. 502.04.01-03, 502.04.01-05, 502.04.02-05

UIM 2026, 502.04, read from the rulebook on 2026-09-08. Read the rule yourself. Every UIM class · where the rulebooks differ · how this site reads a rulebook.

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.

Cite this page

“Runabout GP1, UIM class rules”, BaddJet archive, https://baddjetarchive.com/legality/uim/runabout-gp1/

Add the date you read it.

71 parts read · 4 permitted, 14 with conditions · 2026 rulebook

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