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Class Legality

UIM · runabout

Runabout GP3

UIM 2026, 502.02. A closed-list class. The craft must stay stock except where the rules allow otherwise, so anything unlisted is not permitted.

  • 10Not legal
  • 10OEM part required
  • 19Not permitted, not listed in the rules
  • 1The rules do not say
  • 21Legal, with conditions
  • 10Legal

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
1300cc two-stroke atmospheric, 2000cc four-stroke atmospheric and 200 horsepower (502.02.01-01, 502.02.01-02). GP3 is the ONLY Runabout class with an explicit power cap. The 2-stroke engine section permits the engine to be bored and requires the displacement not to exceed the class designation, so the figure is a ceiling on the engine as raced and not only as the factory built it. 502.02.03.
Minimum weight
216 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 (6)

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 four-stroke exhaust rule.
  • No trim/VTS rule.
  • No hood rule - the GP4 "no other modifications" clause is not repeated and the aftermarket-hood permission is a GP2 addition.
  • How the 200 Hp cap is measured or enforced is not stated.
  • Driveline article 502.02.09 is numbered 01 then jumps to 04 - items 02 and 03 are missing from the published text, so driveline permissions may have been lost in editing.
  • No ballast rule.

What the rules say (71 parts)

10 permitted outright, 21 permitted with stated conditions, 10 refused by a rule we can quote, 10 held to the original part by a rule we can quote, 19 refused by our reading of the class rather than by a quoted rule 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.

What each answer below means

Not legal
This comes off. The rules refuse it in this class.
OEM part required
This comes off. Only the part the manufacturer fitted is allowed here.
Not permitted, not listed in the rules
Treat it as coming off. The class requires the craft to stay stock except where the rules allow otherwise, and this part is not on the list, so this is our reading rather than a rule we can quote at you.
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.

Read the refusals as a list of work. Anything below marked Not legal, OEM part required, or Not permitted has to come off the machine, or go back to the standard part, before it races in this class.

Not legal1 part

Two-stroke exhaust systems must remain entirely of origin, and four-strokes have no exhaust article and stay stock, so on either engine the through-hull outlet flap may not be removed. 502.02.03.03, 502.02-02

Not legal1 part

Unlike Ski GP3, neither Runabout GP3 nor GP2 prints a chamfering allowance, and the class bars grinding or machining any engine component. 502.02.03-02

Not legal1 part

Homologated production craft only - 50 specimens, marketed, conformity certificate. 500.02.01

OEM part required1 part

Two-stroke: the exhaust system must remain entirely of origin, so the original water box is required. Four-stroke: Runabout GP3 has no exhaust article, so the water box stays stock under the class's own stock clause. 502.02-02, 502.02.03-03

OEM part required1 part

Two-stroke: the exhaust system must remain entirely of origin as delivered by the manufacturer. Four-stroke: Runabout GP3 has no exhaust article, so the manifold and head pipe stay stock under the class's own stock clause. 502.02.03-03

OEM part required1 part

Runabout GP3 keeps the original equipment charging system, allows no ignition change it does not list, and unlike GP2 prints no flywheel, alternator or flywheel cover allowance. 502.02.07-04, 502.02.07-05

OEM part required1 part

Crankshaft must remain stock; replacement bearings or bearing shells only, of original type and dimensions. 502.02.04-02

OEM part required1 part

Camshaft(s) must remain stock; replacement bearings of original type and dimensions only. 502.02.04-03

OEM part required1 part

The ORIGINAL EQUIPMENT BASE for that model and type must be used - a relaxation from GP4, which requires the whole seat. 502.02.02-11

OEM part required1 part

The hull may be repaired but not otherwise modified, and a repair may not alter the original configuration by more than 5 mm. 502.02.02-02

Not permitted, not listed in the rules15 parts

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

Not permitted, not listed in the rules1 part

The GP4 prohibition is not repeated and the aftermarket-hood permission is a GP2 addition.

Legal, with conditions1 part

Four-stroke: ducting from the flame arrester to the throttle body or intake manifold inlet is free to modify or replace. Two-stroke: Runabout GP3 omits the ducting sentence Ski GP3 prints, so two-stroke ducting stays original. 502.02.06-02, 502.02.05-01

Legal, with conditions1 part

Two-stroke: a modified or aftermarket filler cap is allowed if no hazard results. Four-stroke: the four-stroke fuel article has no filler cap clause, so the original cap stays. 502.02.05-02, 502.02.06

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

Bored; cylinders interchanged between homologated craft of the same manufacturer. 502.02.03

Legal, with conditions1 part

Must retain original port timing, compression ratio, dome profile, skirt length/shape and material type, and weigh within +/-25.00% of OEM. 502.02.03-04

Legal, with conditions1 part

Rebuild allowed. Stroke and rod length may NOT change. Bearings must keep original type and dimensions. Counterweights must resemble the original with no new holes or pockets. Total assembly weight within +/-5.00% of OEM. Non-ferrous counterweights, crank pins and connecting rods are prohibited. 502.02.03-05

Legal, with conditions1 part

Original diameter maintained. 502.02.09-01

Legal, with conditions1 part

Permitted, subject to the limits UIM applies to every class, namely the sound ceiling, the hull repair tolerance, the fuel specification, and the intake grate, sponson and pump dimensions.

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 required. Max 92 cm each side, 100 mm protrusion, 63.5 mm channel, 63.5 mm below the hull intersection, minimum 6 mm thick. 502.02.02-04, 502.02.02-05, 502.02.02-06, 502.02.02-07

Legal, with conditions1 part

Cover may be changed. 10 mm glossary cap applies.

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

Two-stroke: the cooling system, cooling lines and bypass systems may be modified or aftermarket, with bypass fittings pointing downward and/or rearward. Four-stroke: water-exit derivations may be modified or replaced in the same directions, but no water exit may be added to the head, cylinder or casing. 502.02.03-08, 502.02.04-04

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

CDI unit may be modified or aftermarket; RPM limiter bypassed or eliminated; ignition timing may be changed. OEM charging system required. 502.02.07

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.

Legal1 part

The original bilge pump may be modified, disconnected or removed and aftermarket bilge draining systems are allowed if no hazard is created. 502.02.02.13

UIM 2026, 502.02, 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 GP3, UIM class rules”, BaddJet archive, https://baddjetarchive.com/legality/uim/runabout-gp3/

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71 parts read · 10 permitted, 21 with conditions · 2026 rulebook

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