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Class Legality

IJSBA · runabout

Runabout Open / GP

IJSBA 2024, ROP. A closed-list class. The craft must stay stock except where the rules allow otherwise, so anything unlisted is not permitted.

  • 21Legal, with conditions
  • 32Legal

Read out of the published IJSBA rulebook on 2026-09-07, so confirm anything that decides a purchase. The full note is at the foot of the page.

Running the class

Eligible craft
Starting point is a stock OEM watercraft. Engine, hull and top deck may come from different sources. Aftermarket hulls permitted if homologated at 500 or higher units and IJSBA-approved. Upper decks must be an exact replica of the OEM deck with no change in dimensions or scale, judged by a "silhouette test", with IJSBA the final arbitrator (ROP.3.2).
Displacement limit
2000cc. ROP.4 permits the engine to be bored and requires the displacement not to exceed the class designation, giving 1100cc in Runabout 1100 Open as its example.
Licence or tier
Competitors in classes with turbocharged or supercharged runabout PWC must possess an Expert or Pro licence.
Minimum weight
Four-stroke runabouts equipped with a supercharger or turbocharger must weigh a minimum of 550 lb (ROP.2.1). No minimum stated for naturally aspirated craft.

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 (3)

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 ECU is genuinely absent from the document, verified with a second targeted fetch.
  • No racing number rule, no rider age, no naturally-aspirated minimum weight, no wear ring rule, no lanyard rule, no numeric boost cap.
  • Internal numbering irregularities - a "ROP.9.3" appears within the ROP.8 turbo section, and ROP.5/ROP.6 fuel sections are duplicated.

What the rules say (53 parts)

32 permitted outright and 21 permitted with stated conditions. 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

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.

Legal, with conditions1 part

Carburetors may be modified or aftermarket provided they do not vent or spill fuel at any attitude, with or without the engine running, and jets and needles are inside the carburetor. ROP.5.4

Legal, with conditions1 part

Aftermarket injectors giving increased fuel flow but no airflow increase; additional injectors allowed.

Legal, with conditions1 part

Must fit the OEM battery box and be securely fastened. GP/Open/Freestyle/Sport GP additionally allow an additional battery, a new box and relocation.

Legal, with conditions1 part

The impeller housing may be modified or aftermarket, and the wear ring is the liner inside that housing rather than a part the document names on its own. ROP.9.1

Legal, with conditions1 part

Couplers, bearing housing and driveshaft may be modified or aftermarket provided they keep a 1:1 drive ratio between the engine and the pump. The clause names no material, so a titanium shaft is covered by it. ROP.9.2

Legal, with conditions1 part

Extension may not be wider than the OEM plate, sides must be connected and radiused, and no fins, rudders or skegs. Max extension beyond the OEM plate: 100.00mm (3.94 in) Ski and Sport, 177.80mm (7.00 in) Runabout.

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 12.00mm (0.47 in) below the flat plane of the pump intake area.

Legal, with conditions1 part

Padding and/or mat kits may be added in every class. Where footwells exist they must be BLOCKED OFF during competition with no indentation into the footwell sides.

Legal, with conditions1 part

Permitted if homologated at 500 or higher units and IJSBA-approved. Upper decks must be an exact OEM replica judged by a silhouette test. From Jan 1 2025 the engine block must be from the same manufacturer as the originating top deck.

Legal, with conditions1 part

Replacement bumpers allowed provided no hazard is created. A soft flexible water-spray deflector may attach to the hull sides or bond flange, not extending beyond the perimeter of the OE bumper or side moldings as measured by plumb line. A permanently affixed IJSBA-approved nose bumper is REQUIRED under GEN.8.12.

Legal, with conditions1 part

Allowed in essentially every class. Universal prohibitions: no manually controlled devices that alter cooling water flow during operation, no electronically controlled valves or water injection unless original equipment, and in most stock classes no NEW fittings added to the cylinder head, cylinder or crankcase.

Legal, with conditions1 part

Constant mass only, within the normally exposed areas of the hull, creating no hazard and requiring no modification or relocation of other parts. Water and any other fluid ballast is prohibited in every class.

Legal, with conditions1 part

Separating the bond flange is the only work on the OEM hull the class lists: it must be rejoined by the original method, such as high-strength adhesive, and nothing else on the OEM hull may change. ROP.1.1, ROP.3.2

Legal, with conditions1 part

The class counts any extension mounted on the transom as a trim tab, which may be fixed, automatic or rider controlled but no wider than the planing surface and no more than 100mm (3.94 in.) past its end, as on the trim tab rows. ROP.3.6

Legal2 parts

ROP.7.1: "Ignition system, electrical box, flywheel and flywheel cover may be modified or aftermarket", with no limit on inputs or outputs. On these four-stroke craft (ROP.4) the ECU runs the ignition and sits in the electrical box, and the class also allows added injectors (ROP.5.1), removing the airflow sensor (ROP.5.2) and adding a turbo or supercharger (ROP.8.1), none of which works without a changed ECU. A reading of ROP.7.1: the class document does not name the ECU, where Limited and Superstock do (RAL.7.2, RSS.8.2). ROP.7.1

Legal1 part

Carburetors may be used in addition to or instead of fuel injection, venturi count not exceeding cylinder count. ROP.5.4

Legal1 part

Must meet USCG, SAE J-1928 Marine or UL-1111 Marine backfire flame arrester standards.

Legal1 part

Modified or aftermarket filler cap allowed provided no hazard is created. The FILLER and RELIEF VALVE themselves must stay OEM.

Legal1 part

Engines may be bored and aftermarket piston assemblies are allowed, with displacement kept within the class limit. ROP.4.4

Legal1 part

Plus aftermarket cam gears, tensioners, chain or belt. Camshaft COUNT must match original and conversion to solenoid actuation is prohibited.

Legal1 part

Aftermarket valvetrain components, valve springs and retainers included, are allowed provided the original method of valve activation is kept. ROP.4.3

Legal1 part

The original turbocharger or supercharger may be modified, or an aftermarket unit fitted, so its internals, clutch, belt and pulleys are open, and all hoses and pipes may be modified or aftermarket. ROP.8.1

Legal1 part

Hoods, hatches, covers and cowlings modified or aftermarket, OEM appearance maintained. ROP.3

Legal1 part

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

Legal1 part

Replacement engine mounts are allowed in every class that addresses them. Ski GP, Vintage and Freestyle additionally allow a modified or aftermarket ENGINE BED with the engine repositioned in the hull.

IJSBA 2024, ROP, read from the rulebook on 2026-09-07. Read the rule yourself. Every IJSBA 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

  • Carb jet kit, needle valve, needle valve spring. Corrected 2026-10-01: this row read as unanswered until ROP.5.4 was read against it, and the clause opens the carburetor these parts sit in.
  • Replacement wear ring. Corrected 2026-10-01: this row read as unanswered until ROP.9.1 was read against it, and the clause opens the housing the ring sits in.
  • Titanium driveshaft, impeller housing or stator vane assembly. Corrected 2026-10-01: this row read as unanswered until ROP.9.2 was read against it.
Cite this page

“Runabout Open / GP, IJSBA class rules”, BaddJet archive, https://baddjetarchive.com/legality/ijsba/runabout-open-gp/

Add the date you read it.

53 parts read · 32 permitted, 21 with conditions · 2024 rulebook

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