Not legal1 part
Only reprogramming of the original ECU is allowed. FSKL.5.2
- Aftermarket standalone ECU · Ignition
IJSBA · ski
Four Stroke Ski Lites
IJSBA 2025, FSKL. A closed-list class. The craft must stay stock except where the rules allow otherwise, so anything unlisted is not permitted.
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
- OEM Ski PWC, four-stroke, max 1100cc. "At the time of this posting the only homologated watercraft for Four Stroke Ski Lites is the Yamaha Superjet produced 2021 and after."
- Displacement limit
- 1100cc (FSKL.1). FSKL.1 states the figure of the craft as the manufacturer furnished it, and FSKL.3.1 permits the engine to be bored without restating a ceiling. Both are recorded here as they read.
- Licence or tier
- Not stated.
- 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.
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.
- Rule numbers for FSKL.3.x, 4.x, 5.x and 6.x were mostly not recoverable.
- Intake grate limit printed as 11.00mm (0.47 in) - same conversion conflict as Ski Lites.
- IJSBA Approved aftermarket valves (FSKL) conflicts with the OEM weight/dimension valve rule used in other stock classes.
- No valve-cover, starter motor, engine mount or oil injection rules were found.
What the rules say (53 parts)
9 permitted outright, 16 permitted with stated conditions, 4 refused by a rule we can quote, 9 held to the original part by a rule we can quote and 15 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.
Not legal1 part
Only the 1.00mm / 30-degree chamfer. Abrasive port cleaning is prohibited. FSKL.3.1
Not legal1 part
No internal modification of driveline components including pump stator and reduction nozzle. FSKL.6.2
Not legal1 part
Only ventilation tube changes. Enlarging inlet or outlet openings is prohibited. FSKL.2.12
- Aftermarket hood / engine cover · Hull and handling
OEM part required1 part
Any modification to the water box is prohibited. FSKL.3.6
- Aftermarket waterbox · Exhaust
OEM part required1 part
Intake manifold modification in any portion is prohibited, including screens, filters and spark suppressors.
- Aftermarket intake manifold · Fuel
OEM part required1 part
Fuel injectors must remain stock.
- Aftermarket fuel injectors · Fuel
OEM part required1 part
Fuel injectors and fuel pump must remain stock as furnished by the manufacturer. FSKL.4.2
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. FSKL.1.1, FSKL.4.1
OEM part required1 part
The crankshaft must remain stock; replacement bearings or bearing shells are allowed if they keep their original type and dimensions. FSKL.3.3
OEM part required1 part
Camshaft replacement prohibited. Only bearings, timing changes and adjustable sprockets allowed. FSKL.3.4
- Aftermarket camshafts · Engine
OEM part required1 part
Intercooler assembly and housing must remain OEM.
- Aftermarket intercooler · Forced induction
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.). FSKL.2.2
- Modification of the OEM hull · Hull and handling
Not permitted, not listed in the rules11 parts
Not listed in this class document. Illegal under the closed-list principle.
- Through-hull exhaust outlet / relocation kit · Exhaust
- Aftermarket or modified carburetor · Fuel
- Carb jet kit, needle valve, needle valve spring · Fuel
- Replacement or aftermarket fuel tank · Fuel
- Aftermarket or lightened flywheel · Ignition
- Aftermarket connecting rods · Engine
- Supercharger rebuild internals, clutch, belt, pulleys · Forced induction
- Titanium driveshaft, impeller housing or stator vane assembly · Driveline
- Aftermarket nozzle trim system (pump-mounted) · Driveline
- Rider-controlled or automatic trim tab system · Hull and handling
- Hull extension · Hull and handling
Not permitted, not listed in the rules1 part
FSKL.3.6 lists no aftermarket manifold or head pipe: a manifold previously drilled or tapped may be used once the holes are filled or capped, aftermarket hose or piping may run only from the water box to the exhaust outlet pipe, and the water box and manifold outlet may not be modified. FSKL.1.1, FSKL.3.6
- Aftermarket exhaust manifold / head pipe · Exhaust
Not permitted, not listed in the rules1 part
No clause allows a turbocharger or supercharger, changes not listed are not permitted, and the intake rule bars any change to the airflow downstream of the airflow sensor. FSKL.1.1, FSKL.4.1
- Aftermarket turbocharger or supercharger · Forced induction
Not permitted, not listed in the rules1 part
Not listed in this class document, so illegal under the closed-list rule (FSKL.1.1); FSKL.6.2 also bars internal modification of the reduction nozzle.
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.). FSKL.1.1, FSKL.2.2
- Aftermarket hull or top deck · Hull and handling
Legal, with conditions3 parts
Permitted, subject to the limits IJSBA applies to every class, namely the sound ceiling, the hull repair tolerance, and the intake grate and sponson dimensions.
- Port chamfering service (within the appendix limit) · Engine
- Aftermarket impeller at OEM diameter · Driveline
- Replacement wear ring · Driveline
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.
- Replacement battery · Electrical
Legal, with conditions1 part
Replacement piston assemblies must keep the original compression ratio, dome profile, skirt length and shape and material, and this class states no weight tolerance and no approval route for a non-conforming skirt. FSKL.3.1
- Aftermarket piston assemblies · Engine
Legal, with conditions1 part
IJSBA-approved valves, valve springs and retainers. Conflicts with the OEM weight and dimension rule elsewhere in the document, 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.
- Aftermarket pump cover plate / extension · Driveline
Legal, with conditions1 part
Full-length, with a bar parallel to the drive shaft and radiused leading edges. This document prints the same conflicting limit as Ski Lites, 11.00mm beside 0.47 in (about 11.9mm), so a grate built to 11.00mm passes under either figure; confirm with the inspector before the event.
- Aftermarket intake grate · Driveline
Legal, with conditions1 part
Max TWO. Max 38.00mm drop.
- Aftermarket sponsons · Hull and handling
Legal, with conditions1 part
Replacement trim PLATES only, replica parts offering the same handling characteristics as stock. Material may differ from OEM. FSKL.2.6
- Aftermarket FIXED-position trim tab / ride plate extension · Hull and handling
Legal, with conditions1 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, 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.
- Footholds, tray mats, padding kits · Hull and handling
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.
- Replacement bumpers and water-spray deflectors · Hull and handling
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
Fixed-type or automatic valves only. Thermostats, pressure regulators and solenoids qualify. Manual actuation of any kind during operation is prohibited everywhere.
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.
- Ballast weight kits · Hull and handling
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
Reprogramming of the original ECU with no additional inputs or outputs and original connections retained. FSKL.5.2
- 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
Modified or aftermarket handlepole and mounting bracket, provided it functions as originally designed. Attaching point may be reinforced. FSKL.2.9
- Aftermarket handlepole / pole bracket · Hull and handling
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, FSKL, read from the rulebook on 2026-09-07. Read the rule yourself, Four Stroke Ski Lites. 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.
- Aftermarket intake grate. Corrected 2026-10-04: the Four Stroke Ski Lites row gave 12.00mm, where its class document prints 11.00mm (0.47 in).
Cite this page
“Four Stroke Ski Lites, IJSBA class rules”, BaddJet archive, https://baddjetarchive.com/legality/ijsba/four-stroke-ski-lites/
Add the date you read it.
53 parts read · 9 permitted, 16 with conditions · 2025 rulebook