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Class Legality

IJSBA · runabout

Runabout Superstock

IJSBA 2025, RSS. A closed-list class. The craft must stay stock except where the rules allow otherwise, so anything unlisted is not permitted.

  • 4Not legal
  • 3OEM part required
  • 2Not permitted, not listed in the rules
  • 1Governed by the parent class
  • 15Legal, with conditions
  • 28Legal

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
Four-stroke engines only. Engine blocks may be interchanged between homologated watercraft of ANY OEM manufacturer, except the 2017 Kawasaki SX-R, which must use the engine block furnished by the manufacturer (RSS.3.1).
Displacement limit
Not specified in this document.
Licence or tier
Competitors must possess an Expert or Pro licence to compete in this category (RSS.1).
Minimum weight
Not stated in this document.

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.

  • No displacement limit, no minimum weight, no eligible-model list, no racing number rule, no wear ring rule, no numeric boost limit.
  • Internal tension between RSS.3.5 (retain the OEM intercooler housing for water-supply purposes) and RSS.6.2 (intercooler may be modified or aftermarket).
  • RSS.4, RSS.7 and RSS.9 contain two-stroke provisions that are inert since only four-stroke engines are eligible.

What the rules say (53 parts)

28 permitted outright, 15 permitted with stated conditions, 4 refused by a rule we can quote, 3 held to the original part by a rule we can quote, 2 refused by our reading of the class rather than by a quoted rule and 1 answered by the parent class. 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.
Governed by the parent class
Answered by the parent class rather than here, and the parent is named in the answer.
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

Only replaceable jets, needle valve and needle valve spring changes, choke removal and an aftermarket primer. RSS.5.5

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 2.00mm (0.08 in.). RSS.2.2

Not permitted, not listed in the rules1 part

No aftermarket hull is listed, the craft must remain strictly stock, and a deck repair may not alter the original configuration by more than 2.00mm (0.08 in.). RSS.1.1, RSS.2.2

Governed by the parent class1 part

Not addressed in Runabout Superstock. RSS.1.1 carries every Limited class provision into Superstock unless a Superstock rule says otherwise, so the answer is the Runabout Limited one. RSS.1.1

Legal, with conditions1 part

The exhaust system, water box included, may be aftermarket provided no hazard is created, and RSS.1 admits only four-stroke engines, so the two-stroke rule keeping the original water box does not arise. RSS.1, RSS.3.13

Legal, with conditions1 part

ECU may be modified OR aftermarket, provided it offers no additional inputs or outputs and uses original connections. RSS.8.2

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

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

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

An extension mounted on the transom counts as a trim tab, so it must be fixed in position, no wider than the planing surface and no more than 100.00mm (3.94 in.) past the end of the original planing surface, as on the fixed trim tab row. RSS.2.6

Legal1 part

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

Legal1 part

Fuel pumps and fuel pressure regulators may be modified or aftermarket provided a hazard is not created, and a fuel return line must be fitted in the pump assembly without modifying the tank. RSS.5.6

Legal1 part

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

Legal1 part

Pistons may be aftermarket under the four-stroke engine clause, which sets no weight or profile limit on them. RSS.3.2

Legal1 part

Connecting rods may be modified or aftermarket as part of the crankshaft assembly, whose total weight must stay within +/-5.00% of original. RSS.3.2

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. RSS.6.1

Legal1 part

RSS.6.2. Note the internal tension with RSS.3.5, which asks for the OEM intercooler housing for water-supply purposes.

Legal1 part

The impeller housing, stator vane assembly, pump mounting plate and pump shoe may be modified or aftermarket but not in titanium, and the complete pump and nozzle assembly may be no more than 50.00mm (1.97 in.) longer than original. RSS.10.1

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 2025, RSS, 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.

Cite this page

“Runabout Superstock, IJSBA class rules”, BaddJet archive, https://baddjetarchive.com/legality/ijsba/runabout-superstock/

Add the date you read it.

53 parts read · 28 permitted, 15 with conditions · 2025 rulebook

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