BaddJet Archive Home

Class Legality

UIM · runabout

Runabout GP2

UIM 2026, 502.03. A closed-list class. The craft must stay stock except where the rules allow otherwise, so anything unlisted is not permitted.

  • 5Not legal
  • 9OEM part required
  • 4Not permitted, not listed in the rules
  • 2The rules do not say
  • 30Legal, with conditions
  • 21Legal

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 supercharged four-stroke, 2600cc two-stroke atmospheric and 2600cc four-stroke atmospheric (502.03.01-01). 302.01 lists a flat 2600 cc and will mislead if used alone - the 2000 cc forced-induction sub-limit appears only in 502.03.01. 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. The supercharged four-stroke sub-limit sits in the main criteria rather than in that section. 502.03.03.
Minimum weight
310 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.

  • THE BELASSI BURRASCA APPENDIX DOES NOT EXIST in the 189-page document. The GP2 turbo boost limit is genuinely unpublished.
  • No four-stroke exhaust rule.
  • No intercooler rule.
  • No ballast rule.
  • No explicit statement of whether non-Belassi turbo craft may run.
  • Article 502.03.03 is misnumbered (01, 02, 05, 04, 05...) with two items numbered 05, so an item may be missing.

What the rules say (71 parts)

21 permitted outright, 30 permitted with stated conditions, 5 refused by a rule we can quote, 9 held to the original part by a rule we can quote, 4 refused by our reading of the class rather than by a quoted rule and 2 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

Unlike Ski GP3, neither Runabout GP3 nor GP2 prints a chamfering allowance, and the class bars grinding or machining any engine component. 502.03.03-05

Not legal1 part

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

OEM part required1 part

Two-stroke: the OEM water box must be used unmodified even though the chamber may be aftermarket. Four-stroke: the engine article prints no exhaust allowance, so the original water box stays. 502.03.03-07, 502.03.04

OEM part required1 part

OEM tank, filler and relief valve; pickup, filter and petcock may be aftermarket; fuel cell foam may be added. 502.03.05-04

OEM part required1 part

Crankshaft must remain stock; replacement bearings or bearing shells only, of original type and dimensions. 502.03.04-02

OEM part required1 part

Camshaft(s) must remain stock; replacement bearings of original type and dimensions only. 502.03.04-03

OEM part required1 part

The valves themselves must remain original. 502.03.04-08

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. 502.03-02, 502.02.02-02

OEM part required1 part

Supercharged four-strokes to 2000 cc are admitted, but no article opens the supercharger, so its internals, clutch and pulleys stay original under the class's stock clause. 502.03-02, 502.03.01-01

The rules do not say1 part

NO INTERCOOLER RULE EXISTS for Runabout GP2, in a class where superchargers are legal. Do not assert either way.

Legal, with conditions1 part

Permitted subject to SAE J30R9 high-pressure hose, A.N. threaded fittings or equivalent with non-removable crimped clamps, metal-type filters only on the high-pressure side, and a fuel pump that stops automatically when the engine shuts off. 502.03.05-03

Legal, with conditions1 part

Two-stroke intake manifold assembly may be modified or aftermarket. FOUR-STROKE: the air intake manifold must ALWAYS CONFORM TO THE ORIGINAL MODEL - only reinforcement at the extremities with screws, rivets or a metal side plate is allowed. 502.03.05-01, 502.03.06-02

Legal, with conditions1 part

Two-stroke: flame arresters meeting the USCG, SAE J-1928 Marine or UL-1111 Marine backfire standard must be fitted, aftermarket ones included, and the intake silencer may be removed. Four-stroke: equivalent aftermarket air filters or flame arresters available on the market. 502.03.05-05, 502.03.06-01

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. 502.03.05-04, 502.03.06

Legal, with conditions1 part

Modified or aftermarket, not exceeding 5 cm x 15 cm, with a return line to the tank open at all times. 502.03.05-02

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

Must retain original port timing, compression ratio, dome profile, skirt length/shape and material type, and weigh within +/-25.00% of OEM. 502.03.03-01

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. 502.03.03-02

Legal, with conditions1 part

Two-stroke: a replacement starter motor and bendix may be used. Four-stroke: no starter clause appears for four-strokes, so the original stays. 502.03.03-09

Legal, with conditions1 part

SUPERCHARGED four-stroke up to 2000 cc. Turbocharging is NOT a general GP2 configuration - the sole turbo admission is the Belassi Burrasca, under an appendix that does not exist in the document. 502.03.01-01c, 502.03.04-09

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

Two-stroke: couplers, bearing housing and driveshaft may be modified or aftermarket if a 1:1 drive ratio is kept, but not in titanium. Both engine types may change the floating ring and c-clip on the transmission shaft. 502.03.09-01, 502.03.09-02, 502.03.09-04, 502.03.10-05

Legal, with conditions1 part

Two-stroke: aftermarket nozzle-trim systems may be used. Four-stroke: no trim allowance appears, and no transmission component may be modified. 502.03.09-01, 502.03.10-02

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. 502.03.02, 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. 502.03.02, 502.02.02-11

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

Allowed; four-stroke thermostats and pressure-regulating valves may be bypassed or removed. No fittings added to head, cylinder or casing on four-strokes. 502.03.03-08, 502.03.04-04, 502.03.04-05

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

Carburetors may be modified or aftermarket, so jets, needle valves and their springs may be changed, provided the carburetor does not vent or spill fuel, has no more venturis than cylinders and is not a slide type. 502.03.05.01

Legal1 part

CDI unit may be modified or aftermarket; RPM limiter bypassed or eliminated; ignition timing may be changed. OEM charging system required. 502.03.07-01

Legal1 part

Two-stroke cylinder head AND GASKET may be modified or aftermarket. 502.03.03-06

Legal1 part

The impeller may be modified or aftermarket on both engine types, and the class's own clauses carry no original-diameter condition. 502.03.09-01, 502.03.10-04

Legal1 part

The reverse gate must be REMOVED. 502.03.09.03, 502.03.10.03

Legal1 part

Aftermarket hoods and modified OEM hoods - the single explicit GP2 hull addition over GP3. 502.03.02-01

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. 502.03-02, 502.02.02.13

UIM 2026, 502.03, 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 GP2, UIM class rules”, BaddJet archive, https://baddjetarchive.com/legality/uim/runabout-gp2/

Add the date you read it.

71 parts read · 21 permitted, 30 with conditions · 2026 rulebook

Start
BaddJet Class Legality