Not legal2 parts
Explicitly prohibited by this class document.
- Full porting service (ports reshaped, runners modified) · Engine
- Aftermarket hull or top deck · Hull and handling
IJSBA · runabout
Runabout Naturally Aspirated
IJSBA2025, RNA. A closed-list class. The craft must stay stock except where the rules allow otherwise, so anything unlisted is not permitted.
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 (58 parts)
37 permitted outright, 4 answered by our reading of the class rather than by a quoted rule, 1 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
Exit location unchanged, opening size unchanged.
Not legal1 part
Four-stroke: reprogramming only.
- Aftermarket standalone ECU · Ignition
Not legal1 part
Two-stroke internal modification of any kind is prohibited.
- Aftermarket cylinder (2-stroke) · Engine
Not legal1 part
Two-stroke.
OEM part required6 parts
This class requires the OEM part.
- Aftermarket fuel injectors · Fuel
- Replacement or aftermarket fuel tank · Fuel
- Aftermarket or modified throttle body · Fuel
- Aftermarket or modified crankshaft assembly · Engine
- Aftermarket camshafts · Engine
- Aftermarket hood / engine cover · Hull and handling
OEM part required1 part
Modifying the original waterbox is prohibited.
- Aftermarket waterbox · Exhaust
OEM part required1 part
Intake manifold modifications prohibited.
- Aftermarket intake manifold · Fuel
OEM part required1 part
RNA.5.1 is a no-modification freeze rule, NOT an eligibility ban.
- Aftermarket turbocharger or supercharger · Forced induction
OEM part required1 part
No modifications to the turbo/supercharger system.
- Supercharger rebuild internals, clutch, belt, pulleys · Forced induction
Not permitted, not listed in the rules4 parts
Not listed in this class document. Illegal under the closed-list principle.
- Stinger reducer insert + cooling line · Exhaust
- Aftermarket or lightened flywheel · Ignition
- Aftermarket connecting rods · Engine
- Rider-controlled or automatic trim tab system · Hull and handling
The rules do not say1 part
Not separately addressed.
- Aftermarket intercooler · Forced induction
Legal, within limits4 parts
Permitted subject to the universal limits in ijsba-globals.yaml constants.
- Aftermarket piston assemblies · Engine
- Port chamfering service (within the appendix limit) · Engine
- Aftermarket impeller at OEM diameter · Driveline
- Replacement wear ring · Driveline
Legal, within limits2 parts
Two-stroke only.
Legal, within limits1 part
Two-stroke manifold, head pipe, expansion chamber and the chamber-to-waterbox hose may be aftermarket. Exit location and opening size must not change.
Legal, within limits1 part
Same as Runabout Stock.
- Aftermarket exhaust manifold / head pipe · Exhaust
Legal, within limits1 part
Two-stroke aftermarket carburetors allowed. Four-stroke: jets and needles only.
Legal, within limits1 part
Two-stroke only, max 4 psi.
Legal, within limits1 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.
- Replacement battery · Electrical
Legal, within limits1 part
Listed as allowed in one place and as requiring IJSBA approval per RNA.3.9 in another. Verify.
Legal, within limits1 part
TWO-STROKE craft only. Four-stroke craft get impeller and wear ring only.
Legal, within limits1 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.
- Aftermarket pump cover plate / extension · Driveline
Legal, within limits1 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.
- Aftermarket intake grate · Driveline
Legal, within limits1 part
Max TWO. Max 38.00mm drop.
- Aftermarket sponsons · Hull and handling
Legal, within limits1 part
Replica plates only.
- Aftermarket FIXED-position trim tab / ride plate extension · Hull and handling
Legal, within limits1 part
The handlebar must be padded at the mounting bracket, or the crossbar padded if fitted. This is a tech-inspection item.
- Aftermarket handlebars, throttle, throttle cable, grips, switches · Hull and handling
Legal, within limits1 part
Two-stroke: OEM base required. Four-stroke: aftermarket seat assembly per the Appendix.
- Aftermarket seat assembly / seat base · Hull and handling
Legal, within limits1 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.
- Footholds, tray mats, padding kits · Hull and handling
Legal, within limits1 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.
- Replacement bumpers and water-spray deflectors · Hull and handling
Legal, within limits1 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, within limits1 part
Fixed-type or automatic valves only. Thermostats, pressure regulators and solenoids qualify. Manual actuation of any kind during operation is prohibited everywhere.
Legal, within limits1 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.
- Ballast weight kits · Hull and handling
Legal2 parts
Explicitly permitted by this class document.
Legal1 part
Two-stroke reed valves aftermarket.
- Aftermarket reed petals · Fuel
Legal1 part
Must meet USCG, SAE J-1928 Marine or UL-1111 Marine backfire flame arrester standards.
- Aftermarket flame arrester · Fuel
Legal1 part
Modified or aftermarket filler cap allowed provided no hazard is created. The FILLER and RELIEF VALVE themselves must stay OEM.
- Aftermarket fuel filler cap · Fuel
Legal1 part
Two-stroke CDI modified or aftermarket.
- Aftermarket CDI / ignition box (2-stroke) · Ignition
Legal1 part
RNA.7.2
- ECU reflash / reprogramming of the OEM unit · Ignition
Legal1 part
Aftermarket spark plugs of a different heat range are allowed in every class that addresses them.
- Aftermarket spark plugs of a different heat range · Electrical
Legal1 part
Two-stroke cylinder head and gasket aftermarket.
- Aftermarket cylinder head (2-stroke) · Engine
Legal1 part
Aftermarket steering shaft, steering shaft holder, handlebar holder and steering cables are allowed. Quick-turn modifications that alter the steering ratio are allowed in most stock classes.
- Aftermarket steering shaft, shaft holder, handlebar holder, steering cables · Hull and handling
Legal1 part
The original bilge pump may be modified or disconnected and aftermarket bilge draining systems are allowed, provided no hazard is created.
- Aftermarket bilge draining system · Hull and handling
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.
Legal1 part
Replacement starter motor and bendix are allowed in every class that addresses them.
- Replacement starter motor and bendix · Electrical
IJSBA 2025, RNA, read from the rulebook on 2026-09-07, not verified by a racer. Read the rule yourself, Runabout Naturally Aspirated. Every IJSBA 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.
58 parts read · 37 permitted outright · 2025 rulebook