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Class Legality

IJSBA · freestyle

Freestyle

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

  • 22Legal, with conditions
  • 39Legal

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
One homologated PWC per competitor. Ski, Sport and Runabout hull types all permitted. Stock, Limited, Superstock or Modified craft may be used. Crankcases determine the originating watercraft model for identification.
Displacement limit
1500cc naturally aspirated four-stroke, 950cc forced-induction four-stroke, 900cc two-stroke in Amateur and 1200cc two-stroke in Pro (FREST.3). FREST.3 permits the engine to be bored and states both ceilings in the same paragraph, 1200cc for Pro and 900cc for Amateur, so the figures are a ceiling on the engine as raced and not only as the factory built it.
Licence or tier
Not stated. One person per watercraft during competition.
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 (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.

  • No personal safety-equipment, rider age/licence or minimum weight rules appear in this document.
  • Homologation is referenced but never defined and no production-unit count is given.
  • Rule-number conflict - footwell blocking cited once as FREST.2.2 and once as FREST.2.12.
  • FREST.9.x forced-induction rules exist but no boost PSI cap was recoverable.

What the rules say (61 parts)

39 permitted outright and 22 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

The exhaust system, which this clause names as the manifold, head pipe, expansion chamber, waterbox and mufflers, may be modified or aftermarket, and an insert in the stinger is part of it. No tuned portion of the exhaust may protrude outside the hull. FREST.3.7

Legal, with conditions1 part

The fuel tank may be modified or aftermarket provided the craft cannot vent or spill fuel at any attitude and the tank is securely fastened to the hull, and the filler may be relocated. The same clause also keeps the narrower wording that limits a replacement to an unmodified tank from another homologated PWC or a race director approved aftermarket tank. It sits in the two-stroke fuel section, and the four-stroke section has no tank clause. FREST.4.4, FREST.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

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. FREST.6.1

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. FREST.6.2

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

Legal if it does not exceed OEM upper-deck length/width. Max 165.1mm (6.5 in) shorter than OEM length, within 50.8mm (2.0 in) of OEM width. Ski deck absolute minimums 193cm x 68.5cm x 53.3cm.

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

The hull may be modified within the plumb-bob outline of the original upper deck's bond flange, bumpers removed, and may be no smaller than the top deck's minimum measurements. A separated bond flange is rejoined by the original method, and hazardous fins, rudders and skegs are barred. FREST.2.2, FREST.2.3

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. FREST.2.7

Legal1 part

The exhaust system may be modified or aftermarket on every engine, the two-stroke manifold and head pipe and the four-stroke manifold and connecting pipes included. FREST.3.7, FREST.7.8

Legal1 part

Carburetors may be modified or aftermarket if they do not vent or spill fuel, with no more venturis than cylinders and no slide-type carburetors. FREST.4.1, FREST.8.4

Legal1 part

The carburetor may be modified or aftermarket provided it cannot vent or spill fuel at any attitude, which covers its jets, needle valves and needle valve springs. FREST.4.1, FREST.8.4

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. FREST.3.1, FREST.7.4

Legal1 part

A two-stroke crankshaft assembly may be modified or aftermarket with stroke and rod length changed, and a four-stroke crankshaft may be modified or aftermarket within +/-5.00% of original weight, keeping the original stroke above 1600cc. FREST.3.4, FREST.7.5

Legal1 part

Aftermarket camshafts are allowed if the original number of camshafts, the original bearing type and dimensions and the original method of valve activation are kept, and cam timing may be changed. FREST.7.3

Legal1 part

Aftermarket valvetrain components, valve springs and retainers included, are allowed provided the original method of valve activation is kept. FREST.7.3

Legal1 part

Two-stroke cylinders may be modified or aftermarket and four-stroke ports may be changed in diameter and shape, so a chamfer within the appendix limit is covered. FREST.3.3, FREST.7.2

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. FREST.9.1

Legal1 part

Sport and Runabout seat assembly modified or aftermarket. Presence of a seat classifies the craft as Sport or Runabout by dimension.

Legal1 part

Freestyle prints no hood clause, but engine covers, storage covers, hatches and instrument cowlings may be modified or aftermarket if no hazard is created, and the top deck may be modified or aftermarket within its size limits. FREST.2.2, FREST.2.16

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, FREST, 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

  • Replacement wear ring. Corrected 2026-10-01: this row read as unanswered until FREST.6.1 was read against it, and the clause opens the housing the ring sits in.
  • Stinger reducer insert + cooling line. Corrected 2026-10-01: this row read as unanswered until FREST.3.7 was read against it, and the clause opens the whole exhaust system.
  • Titanium driveshaft, impeller housing or stator vane assembly. Corrected 2026-10-01: this row read as unanswered until FREST.6.2 was read against it.
Cite this page

“Freestyle, IJSBA class rules”, BaddJet archive, https://baddjetarchive.com/legality/ijsba/freestyle/

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61 parts read · 39 permitted, 22 with conditions · 2025 rulebook

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