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Runabout GP2

IHRA · runabout

Runabout GP2

IHRA2026, Y. 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.

  • The class criteria admit two-stroke watercraft and section Y publishes no two-stroke engine rules, only the Y.3.2 induction article. Under the closed-list principle that leaves a two-stroke entry with almost nothing permitted on the engine, which is unlikely to be the intent and is what the document says.
  • The section's own introduction describes the class as intended for stock runabout watercraft up to 1800cc. Y.1, six lines later, sets the ceiling at 2000cc for four-stroke engines. Both figures are printed and neither is withdrawn, so both are recorded here and the `displacement` block above holds the one the class criteria state.
  • The phrase "Subject to class availability" is doing the work of an eligibility list here and is defined nowhere in the rulebook.
  • Y.2.6 states a head gasket thickness tolerance of 20 per cent, which is the same figure Ski Modified uses and a different shape of rule from the contradictory millimetre figures in the Lites classes.

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 or top deck article.
  • No two-stroke ENGINE article. Every article under Y.2, from pistons to valves, describes a four-stroke. The only place carburetted craft are addressed at all is Y.3.2, on induction. Runabout GP3 by contrast splits its engine articles by engine type.

What the rules say (77 parts)

31 permitted outright, 36 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

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

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. Y.3.2

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. Y.4.1

Not permitted, not listed in the rules36 parts

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

Legal, within limits1 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. Y.3.2

Legal, within limits1 part

No modifications downstream of the airflow sensor. INTAKE MANIFOLD MUST REMAIN AS ORIGINALLY EQUIPPED. Ribbon delete permitted if airflow is not increased. Y.3.1

Legal, within limits1 part

Reprogramming the original unit is the permitted route, with no additional input, output or sensor. Y.4.1

Legal, within limits1 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, within limits1 part

Must retain original compression ratio, dome profile and material type. Boring and stroke modifications within displacement limits, and ports must not be abrasively cleaned. Y.2.1

Legal, within limits1 part

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

Legal, within limits1 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, within limits1 part

May be replaced within OEM specifications. J.18.3

Legal, within limits1 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, within limits1 part

Must replicate the original parts and handling characteristics. Material may differ if no hazard. Y.5.2

Legal, within limits1 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, within limits1 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, within limits1 part

OE seat base must remain in use, with height change and cover thickness each limited to 12.7 mm. U.6.1

Legal, within limits1 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, within limits1 part

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

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, Y, read from the rulebook on 2026-09-11, not verified by a racer. Read the rule yourself. Every IHRA 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.

77 parts read · 31 permitted outright · 2026 rulebook

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