BaddJet Archive Home

Class Legality

IHRA · runabout

Runabout GP3

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

  • 1Not legal
  • 16OEM part required
  • 30Not permitted, not listed in the rules
  • 23Legal, with conditions
  • 9Legal

Read out of the published IHRA rulebook on 2026-09-11, so confirm anything that decides a purchase. The full note is at the foot of the page.

Running the class

Eligible craft
Most two-stroke watercraft under 800cc and four-stroke watercraft under 1100cc, subject to class availability. No model-year list is published.
Displacement limit
800cc two-stroke and 1100cc naturally aspirated four-stroke (Z.1). Z.2.1 permits the engine to be bored within the displacement restrictions and requires the displacement not to exceed the class designation, so the figures are a ceiling on the engine as raced.
Licence or tier
Not stated.
Minimum weight
Not stated.

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 (2)

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.

  • Z.3.1 permits a non-conforming two-stroke piston with advance written approval and names no approver and no standard.
  • The phrase "Subject to class availability" is doing the work of an eligibility list here, as it does in Runabout GP2, and is defined nowhere.

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.

  • No hull-substitution or top deck rule. The hull article, Z.10, covers only ventilation and seat.

What the rules say (79 parts)

9 permitted outright, 23 permitted with stated conditions, 1 refused by a rule we can quote, 16 held to the original part by a rule we can quote and 30 refused by our reading of the class rather than by a quoted rule. 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.
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

Bolts, nuts and washers may not be substituted with titanium unless originally equipped. Locking mechanisms are allowed. J.7

OEM part required1 part

Z.3.3 keeps a two-stroke exhaust system stock, with only a stinger insert to reduce its inside diameter, and Z.2.5 lists no aftermarket manifold or head pipe for a four-stroke, allowing a manifold previously drilled or tapped once the holes are filled or capped, and flange removal. J.1, Z.2.5, Z.3.3

OEM part required1 part

The original carburetor body must stay, with only the jets, needle valves and springs replaceable, the choke removable and an aftermarket primer allowed. Z.4.2, Z.5.1

OEM part required1 part

Two-stroke entries: Original tank, pickup, filler, filter, tap assembly, relief valve unmodified. The petcock may be bypassed. Z.5.2

OEM part required1 part

The original ECU must stay and may only be reprogrammed, with no additional input, output or sensor, so an aftermarket or standalone box is not legal here. Z.6.1

OEM part required1 part

Z.7.1 lets a two-stroke entry's control unit, its CDI box, be modified with no input or output added, but names no aftermarket unit, so the original box stays. J.1, Z.7.1

OEM part required1 part

No aftermarket unit is listed. Z.1 admits four-stroke engines only as naturally aspirated, while Z.9.1 lets supercharger components be reinforced for safety and allows replacement parts with the original gear ratios kept; neither withdraws the other. J.1, Z.1, Z.9.1

OEM part required1 part

The original seat base must stay in use. The cover may be replaced, but seat height may change by no more than 12.7 mm either way and the cover may add no more than 12.7 mm. Z.10.2

OEM part required1 part

The hull may be repaired but not otherwise modified, and a repair may not move it more than 2 mm (0.08 in) from its original configuration. J.1, J.13

Not permitted, not listed in the rules29 parts

On a closed list an unlisted modification is not permitted. A.2.2, J.1

Not permitted, not listed in the rules1 part

Z.2.5 allows previously drilled manifolds if sealed and the removal of exhaust flanges on four-strokes; Z.3.3 keeps the two-stroke exhaust stock with a stinger insert; neither names the outlet, and under J.1 and A.2.2 an unlisted modification is not permitted. Z.2.5, Z.3.3

Legal, with conditions1 part

Only the jets, needle valves and springs replaceable, the choke removable and an aftermarket primer allowed, and nothing else on the carburetor may be changed. Z.4.2, Z.5.1

Legal, with conditions1 part

Every engine must run a flame arrester meeting USCG, UL-1111 or SAE J-1928 rather than the OEM one, and where a ribbon is the OEM arrester it may be removed if airflow does not increase and the air filter still suppresses flame. Z.4.1, Z.4.2, Z.5.1

Legal, with conditions1 part

The ducting between the flame arrester and the throttle body may be modified or aftermarket, or only as far as the airflow sensor where one is fitted, and nothing downstream of the sensor may change. No cold air system is named, so the allowance stops at that ducting. Z.4.1

Legal, with conditions1 part

Reprogramming the original unit is the permitted route, with no additional input, output or sensor. Z.6.1

Legal, with conditions1 part

Gauges may be modified or removed provided no hazard is created and any resulting hole is sealed. Section J permits modification and removal and never addresses adding an aftermarket instrument. J.15

Legal, with conditions1 part

J.7, in the general rules for every class, names wiring as replaceable with aftermarket options, which overrides the closed-list default and covers replacement wiring. Connectors are not named on their own, and J.7 does not open added inputs or outputs, a different harness design or an ECU. J.7

Legal, with conditions1 part

On four-stroke entries as Runabout GP2 at Y.2.1. On two-stroke entries the piston must keep its port timing, compression ratio, dome profile, skirt length and shape and material type, a non- conforming piston needs advance written approval, and weight stays within 25 per cent. Z.3.1

Legal, with conditions1 part

Repairs are allowed for a crack or puncture, but only one damaged area affecting one cylinder bank. No other modification. J.11

Legal, with conditions1 part

Under Z.9.1 supercharger components may be reinforced for safety and replaced, keeping the original gear ratios, yet Z.1 admits four-stroke engines only as naturally aspirated, so the section contradicts itself. Z.1, Z.9.1

Legal, with conditions1 part

May be modified or replaced with an aftermarket part. The original diameter must be maintained in Stock class, and the rulebook never defines which classes that is. J.18.2

Legal, with conditions1 part

May be replaced within OEM specifications. J.18.3

Legal, with conditions1 part

Aftermarket or modified, full-length type with at least one bar parallel to the driveshaft, dropping no more than 12.00mm (0.47 in) below the flat plane of the pump intake. J.18.1

Legal, with conditions1 part

Must replicate the original parts and handling characteristics. Material may differ if no hazard. Z.8.2

Legal, with conditions1 part

Braking devices may be disabled for safety, and reverse buckets and trim motors may be removed or modified to disable them, provided no hazard is created. J.18.4

Legal, with conditions1 part

Aftermarket, modified, repositioned or removed. Up to two, each no longer than 36 in (91.45 cm), protruding no more than 3.94 in (100 mm) horizontally, at least 6 mm thick with radiused leading edges, and not attached to a planing surface. J.16

Legal, with conditions1 part

Seat height may change by no more than 12.7 mm and the cover may be no thicker than 12.7 mm. Z.10.2

Legal, with conditions1 part

Replacement bumpers and side rails may be used provided they create no hazard. A permanently affixed nose bumper remains required. J.13, I.17

Legal, with conditions1 part

May be added to adjust handling. Constant mass only, and no other part may be modified to carry it. J.19

Legal, with conditions1 part

On two-stroke entries no fitting may be added to the cylinder head, cylinder or crankcase, only fixed or automatic valves are allowed, and electronic valves and water injection are prohibited unless OEM. Z.3.2

Legal1 part

J.7, in the general rules for every class, names hoses and clamps as replaceable with aftermarket options, which overrides the closed-list default and covers an aftermarket fuel hose. Fittings are not named on their own. J.7

Legal1 part

May be replaced, as may starters and oil injection systems, with the oil injection system removable or disconnectable. J.8

Legal1 part

Grips, throttle and cables may be modified or aftermarket. The bar must be padded at the mounting bracket or the crossbar padded. J.17.1

Legal1 part

Steering shaft, holder, handlebar holder and cables may be aftermarket, and quick-turn modifications are allowed. J.17.2

Legal1 part

The bilge pump may be modified or disconnected and aftermarket bilge draining systems are permitted, provided they create no hazard. J.10

IHRA 2026, Z, read from the rulebook on 2026-09-11. Read the rule yourself. Every IHRA 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.

What we corrected here, and when

  • Aftermarket expansion chamber / tuned pipe (2-stroke). Corrected 2026-09-30: this cell read allowed with limits on a note about drilled four-stroke manifolds and a stinger insert, neither of which is an aftermarket chamber, so the row contradicted its own lead sentence.
  • Aftermarket supercharger. Corrected 2026-10-05: the Runabout GP3 aftermarket supercharger row left out the replacement parts that Z.9.1 allows, and now notes that Z.1 admits only naturally aspirated four-strokes.
  • High-pressure fuel line and fittings. Corrected 2026-10-02: the Runabout GP3 row read the closed-list default and refused a fuel hose, which J.7 allows in every class; until 2026-10-31 this line wrongly excepted the drag section, where J.7 applies too.
  • Relocated or aftermarket through-hull outlet. Corrected 2026-09-30, Runabout GP3: the cell had been graded from a note about manifolds and inserts.
  • Supercharger internals, clutch and pulleys. Corrected 2026-10-05: on supercharger internals for Runabout GP3, this row now carries the Z.9.1 allowance for replacement parts and the clash with the naturally aspirated limit in Z.1.
Cite this page

“Runabout GP3, IHRA class rules”, BaddJet archive, https://baddjetarchive.com/legality/ihra/runabout-gp3/

Add the date you read it.

79 parts read · 9 permitted, 23 with conditions · 2026 rulebook

Start
BaddJet Class Legality