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Class Legality

IJSBA · runabout

Runabout Naturally Aspirated

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

  • 5Not legal
  • 12OEM part required
  • 6Not permitted, not listed in the rules
  • 24Legal, with conditions
  • 13Legal

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 Stock Class watercraft combined with two-stroke Limited Class watercraft. Models per the homologation appendix.
Displacement limit
Two-stroke: must not exceed the class designation (RNA.4.1). Four-stroke: no cc figure stated.
Licence or tier
Not stated.
Minimum weight
Not stated in this document (note this DIFFERS from Runabout Stock's 35 lb tolerance).

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.

  • LARGEST UNCERTAINTY IN THE SET. The document does not match its filename.
  • Internal contradiction on valve springs - listed as allowed in one place and as requiring IJSBA approval per RNA.3.9 in another.
  • No weight rule, no rider requirements, no ballast, no hood/hatch, no racing numbers, no separate ride plate article, no intercooler article.

What the rules say (60 parts)

13 permitted outright, 24 permitted with stated conditions, 5 refused by a rule we can quote, 12 held to the original part by a rule we can quote and 6 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.

OEM part required1 part

Modifying the original waterbox is prohibited.

OEM part required1 part

A four-stroke craft must keep its fuel injectors and fuel pump stock as furnished by the manufacturer. Only a two-stroke entry may fit an aftermarket fuel-injection system, built to the high-pressure hose, fitting and filter rules. RNA.5.3, RNA.6.3

OEM part required1 part

No throttle body change is listed, the intake rule bars any change to the airflow downstream of the airflow sensor, and every portion of the intake manifold must remain as originally equipped. RNA.1.1, RNA.5.1

OEM part required1 part

The crankshaft must remain stock; replacement bearings or bearing shells are allowed if they keep their original type and dimensions. RNA.3.3, RNA.4.4

OEM part required1 part

Camshafts must remain stock; timing adjustment allowed. RNA.3.4

OEM part required1 part

No intercooler change is listed, and on a craft with factory forced induction the turbocharger or supercharger system may not be modified at all, so the intercooler stays as supplied. RNA.1.1, RNA.5.1

OEM part required1 part

No hood change is listed, and even the engine compartment ventilation tubes must remain as originally equipped, so the hood stays OEM. RNA.1.1, RNA.2.13

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.). RNA.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.). RNA.1.1, RNA.2.2

Legal, with conditions1 part

RNA.4.7 lets the exhaust manifold, head pipe, expansion chamber, gaskets and the hose to the OEM waterbox be modified, altered or aftermarket, keeping the exhaust gas location and the original exit opening size, with the OEM waterbox unmodified and no tuned portion outside the hull. RNA.4.7

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

Listed as allowed in one place and as requiring IJSBA approval per RNA.3.9 in another, and which one governs is not settled.

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.

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

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, RNA, 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 Naturally Aspirated, IJSBA class rules”, BaddJet archive, https://baddjetarchive.com/legality/ijsba/runabout-naturally-aspirated/

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60 parts read · 13 permitted, 24 with conditions · 2025 rulebook

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