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Runabout GP4

UIM · runabout

Runabout GP4

UIM2026, 502.01. A closed-list class. The craft must stay stock except where the rules allow otherwise, so anything unlisted is not permitted.

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 exhaust rule at all.
  • No ballast rule.
  • No explicit statement on whether GP4 four-strokes may be bored.
  • No model or model-year eligibility list.

What the rules say (52 parts)

23 permitted outright, 13 answered by our reading of the class rather than by a quoted rule, 0 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.

Not permitted, not listed in the rulesOur reading, not a rule we can quote at you. This class requires the craft to stay stock except where the rules allow otherwise, and this part is not on the list.

Not legal1 part

NO MODIFICATIONS TO THE HOOD are allowed beyond those listed. 502.01.02-15

OEM part required1 part

THE HEAD GASKET MUST BE ORIGINAL - stated expressly and uniquely for Runabout GP4. 502.01.03-01

Not permitted, not listed in the rules11 parts

Not listed in this class. Illegal under the class's own stock clause.

Not permitted, not listed in the rules1 part

Only the manual trim system substitution.

Legal, within limits1 part

Equivalent aftermarket air filters/flame arresters available on the market; the flame arrestor/air restrictor DOWNSTREAM of the throttle body may be removed. 502.01.04

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

Original diameter maintained. 502.01.06-01

Legal, within limits1 part

Permitted subject to the universal limits in uim-globals.yaml constants.

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

TWO REAR SPONSONS required. Max 92 cm each side, 100 mm protrusion, 63.5 mm channel, 63.5 mm below the hull intersection, minimum 6 mm thick.

Legal, within limits1 part

The cover may be changed, including covering seat and backrest as a single piece, provided the shape and dimensions are unaltered. The glossary caps aftermarket seat covers at 10 mm thickness and forbids altering the original shape.

Legal, within limits1 part

Start/stop switches may be replaced or aftermarket; the kill switch may be moved from its original position. 502.01.02-16/17

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

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.

UIM 2026, 502.01, 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.

52 parts read · 23 permitted outright · 2026 rulebook

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