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Ski Modified

IJSBA · ski

Ski Modified

IJSBA2024, SKM. A closed-list class. The craft must stay stock except where the rules allow otherwise, so anything unlisted is not permitted.

Open questions on this class (5)

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.

  • Document year conflict - filename 2024, body reads 2023.
  • SKM.6, SKM.7 and SKM.8 do not exist. There is NO ignition/ECU section, NO dedicated exhaust-system section and NO flame arrester rule in this class document.
  • No port-chamfering allowance was returned, unlike the stock classes.
  • Sponson drop 63.5mm here vs 38.00mm in the stock classes it says Kawasaki hulls inherit from.
  • Deck height figure returned as ".155mm (.06in)" - almost certainly a decimal typo for 1.55mm.

What the rules say (50 parts)

29 permitted outright, 10 answered by our reading of the class rather than by a quoted rule, 5 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.

OEM part required1 part

Throttle bodies must remain stock. No throttle plate angle change, no housing modification, NO PHENOLIC OR ALUMINIUM SPACERS behind the throttle body. SKM.5.2

OEM part required1 part

Camshaft stock. Timing may be changed and adjustable sprockets fitted in the 1101-1500cc category.

Not permitted, not listed in the rules9 parts

Not listed in this class document. Illegal under the closed-list principle.

Not permitted, not listed in the rules1 part

No waterbox allowance in SKM.

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.

Legal, within limits1 part

Aftermarket springs and retainers in the 0-1100cc category ONLY. In 1101-1500cc, springs and retainers must be OEM. SKM.4.5

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.

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.

Legal, within limits1 part

Max TWO, 63.5mm drop per SKM.2.4, BUT the class also says Kawasaki hulls follow Ski Stock rules and Yamaha hulls follow Four Stroke Ski Lites rules. Unresolved conflict.

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.

Legal, within limits1 part

IJSBA-approved aftermarket hulls and top decks permitted, must display IJSBA-recognised hull identification. SKM.1.1

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.

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

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 2024, SKM, read from the rulebook on 2026-09-07, not verified by a racer. Read the rule yourself. 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.

50 parts read · 29 permitted outright · 2024 rulebook

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