WILLIAMS 435 SportJet Sport
(Rotax 1503 Engine)
Technical guide, maintenance and spare parts
The Williams SportJet 435 Sport equipped with the BRP Rotax 1503 4-TEC 150 HP engine is the high-performance version of the SportJet 435 of this generation.
Thanks to its 1,494 cc three-cylinder engine, this version offers acceleration and performance superior to the Standard SportJet 435 equipped with the 90 HP Rotax ACE 903.
With an advertised top speed of up to approximately 84 km/h (52 mph), the SportJet 435 Sport 1503 is particularly well-suited for water sports, while retaining its primary function as a yacht tender.
The SportJet 435 model has existed with several engine configurations depending on the year and version. This guide covers the naturally aspirated 150 HP Rotax 1503 4-TEC configuration, not the Standard ACE 903 or the Sport ACE 1630 versions. Identify the year, horsepower, and engine serial number before ordering any parts.
Find parts for your WILLIAMS SportJet 435 Sport – Rotax 1503
- Engine parts
- Fuel system
- Ignition
- Sensors
- Electrical parts
- Cooling
- Oil and filters
- Seals and gaskets
- Jet pump parts
- Other
The different versions of the Williams SportJet 435
This article is dedicated to the SportJet 435 Sport with Rotax 1503 engine. The three configurations below help distinguish the engine types, without replacing the need to check the engine plate.
- SportJet 435 Sport – Rotax 1503 (described in this article)
- SportJet 435 Standard – Rotax ACE 903
- SportJet 435 Sport – Rotax ACE 1630
SportJet 435 Sport – Rotax 1503 (described in this article)
This generation of the SportJet 435 Sport is equipped with the BRP Rotax 1503 4-TEC 150 HP engine, a 1,494 cc four-stroke, three-cylinder engine. In this Williams configuration, it is a naturally aspirated version, without a supercharger.
This engine provides more power and torque than the 90 HP Standard ACE 903, particularly for water activities and uses requiring better acceleration. Engine parts differ; some part numbers may be common, but this must be verified part by part.
See our Rotax 1503 engine guide.
SportJet 435 Standard – Rotax ACE 903
The Standard version is equipped with the BRP Rotax ACE 903 90 HP engine. This four-stroke, three-cylinder engine is also used on the TurboJet 285 and 325, as well as the SportJet 345 and 395 described in our guides.
Find its specifications and parts in our article on the Williams 435 Standard with Rotax ACE 903 engine.
SportJet 435 Sport – Rotax ACE 1630
On newer versions, particularly from 2021 onwards depending on the configuration, the SportJet 435 Sport may be equipped with the Rotax ACE 1630. Always confirm the engine actually installed without relying solely on the year. Many parts are specific: the name "SportJet 435" is not enough to identify a part.
See our Rotax 1630 engine guide.
How do I know which version of the SportJet 435 I have?
Check the year of manufacture, the engine model on the plate or certificate of conformity, the horsepower, and the serial number of the tender or engine. Photos can help with identification but do not replace checking the actual engine. Two visually similar SportJet 435s may use different mechanical parts.
Technical specifications of the Williams SportJet 435 Sport – Rotax 1503
- Length overall: 4.35 m.
- Beam: 1.93 m.
- Height: 1.04 m.
- Draft: 0.36 m.
- Dry weight: 480 kg.
- Engine: BRP Rotax 1503 4-TEC.
- Displacement: 1,494 cc.
- Power: 150 HP.
- Propulsion: Jet pump.
- Capacity: 7 people.
- Fuel tank: 60 liters.
- Top speed: up to 84 km/h (52 mph).
- Maximum load: 633 kg.
- Tube compartments: 5.
- CE Category: C.
- Recommended yacht: approx. 20 m and above.
Specifications may vary slightly depending on the year of manufacture, equipment, and tender configuration.
Maintenance schedule – Williams SportJet 435 Sport / Rotax 1503
The Williams maintenance program provided for this article is mainly based on three intervals: 50 hours or 1 year, 100 hours or 1 year, and 200 hours or 2 years. For operations directly related to the Rotax 1503 engine, also consult the corresponding engine manual. A dash indicates that no operation is listed in that cell of the provided table, not that general maintenance is unnecessary.
| Item | 50 h / 1 year | 100 h / 1 year | 200 h / 2 years |
|---|---|---|---|
| Engine oil and filter | Replace | Replace | — |
| Engine rubber mounts | Inspect | Inspect | — |
| Engine anti-corrosion protection | Regular lubrication* | Regular lubrication* | — |
| PTO sleeve / seal | — | — | Replace** |
| Exhaust system | Inspect | Inspect / clean | — |
| Exhaust flushing | Regular cleaning*** | Regular cleaning*** | — |
| Cooling hoses and clamps | Inspect | Inspect | — |
| Coolant | Inspect | Inspect | Replace |
| Throttle body | Inspect | Inspect | — |
| Fuel system and lines | Inspect | Inspect | — |
| Engine fault codes | Inspect | Inspect | — |
| Air filter | Inspect / replace if necessary | — | — |
| Spark plugs | Inspect | Inspect | Replace |
| Ignition coils | Inspect | Inspect | Inspect |
| Electrical connections | Inspect | Inspect | Inspect |
| Engine stop switch | Inspect | Inspect | Inspect |
| Steering cable and connection | Inspect | Inspect | — |
| Steering nozzle bushings | Inspect | Inspect | — |
| Carbon ring / driveshaft bellows | Inspect | Inspect | — |
| Propulsion control and cables | Inspect | Inspect | — |
| Reverse bucket | Lubricate | Lubricate | — |
| Driveshaft / jet pump splines and PTO | Inspect / lubricate | — | — |
| Shaft seal, sleeve, and O-ring | Inspect | — | Replace |
| Impeller and wear ring clearance | Inspect | Inspect | — |
| Sacrificial anode | Regular check**** | Regular check**** | Regular check**** |
| Intake grate / plate | Inspect | — | — |
* For saltwater use, anti-corrosion protection for engine compartment metal components every 10 operating hours.
** The PTO sleeve and seal must be replaced at 200 hours, regardless of age.
*** The exhaust system must be flushed daily after use in saltwater or polluted water.
**** The sacrificial anode must be checked monthly, and every two weeks in saltwater. It must be replaced when necessary.
Important points for saltwater use
A SportJet used as a yacht tender is exposed to seawater. Corrosion prevention is therefore particularly important. After use, pay special attention to the following items, according to manufacturer procedures:
- flushing the cooling system;
- flushing the propulsion unit;
- checking the anode;
- cleaning the engine compartment;
- anti-corrosion treatment of metal components;
- checking electrical connections;
- checking the impeller and intake grate.
See our engine flushing guide as a supplement to the WILLIAMS and Rotax manual specific to your configuration.
Common parts for the WILLIAMS SportJet 435 Sport – Rotax 1503
The OEM part numbers in this selection are used to identify the parts being replaced; they do not automatically denote original parts. The two oil filters with part number 420956744 below are common to both 1503 and 1630 engines.
The iNR connector only concerns tenders equipped with this option. For the cylinder head, check the valves, seats, keepers, springs, and retainers before choosing a variant.
| 1503 4-TEC head gasket | 420641110 / 420950770 | Block / cylinder head sealing. |
| Valve cover gasket | 290950820 / 420950820 | Valve cover sealing. |
| 4-TEC timing chain | 420898042 | Timing synchronization. |
| 1503 oil pump bellows | 420832648 | Oil circuit |
| 1503 connecting rod bearing kit | Not specified | Bottom end rebuild; choose between standard or +0.50mm repair size after measurements by a professional. |
| 1503 intake / exhaust valve | 420254682 ; 420254293 / 420254298 | Targeted replacement; intake, exhaust, or pair, compare geometry and grooves. |
| Kit of 12 single-groove valves | 420254682 / 420253163 | Cylinder head rebuild only if the valve train assembly uses the corresponding single-groove configuration. |
| Kit of 12 triple-groove valves | 420254298 / 420254682 | Cylinder head rebuild; confirm triple groove. Do not automatically substitute for a single-groove kit. |
| 1503 valve stem seals | 420630200 / 420630202 | Sealing around valve stems; set of 6 or 12 depending on variant. |
| 1503 4-TEC magneto stator | 420889721 / 420889720 / 290889720 | Electric power generation; for 2002–2017 Sea-Doo applications; verify mounting and Williams connector. |
| Complete 1503 engine gasket kit | Not specified | Engine sealing during a rebuild; verify BLACK/RED versions and exact contents for your configuration. |
| 4-TEC forged connecting rod | 420917516 | Transmits force from piston to crankshaft; sold individually or by 3, verify reference and dimensions. |
| Connecting rod and crankshaft bearings | 420933456 / 420933466 / 420933523 | Bottom end rebuild; variants and STD/repair sizes to be determined by measurement based on journal surfaces. |
| Intake air temperature sensor | 420222427 / 420222423 | Air temperature measurement for engine management; compare reference and connector. |
| Complete Rotax 1503 piston kit, STD or +0.50mm | 420890244 | 3-cylinder kit with pistons, rings, pins, and circlips |
| WSM 010-862K piston kit, STD size | 420890244 / 420892735 ; WSM 010-862K | Piston, rings, pin, and circlips |
Common problems with the WILLIAMS SportJet 435 Sport – Rotax 1503
The following symptoms may have multiple causes. These guidelines assist in inspections but do not replace professional diagnosis nor automatically justify part replacement. Interventions on fuel, electrical, and moving parts must be performed safely, according to the manual, and by a professional when necessary. (FMT)
- Engine does not start: battery, electrical connections, battery switch, safety lanyard, fuses, relays, fuel supply, spark plugs, ignition coils, or sensors. A battery capable of powering accessories may not provide sufficient voltage during cranking.
- Engine misfires: systematically check ignition, fuel supply, sensors, and connections before replacing parts.
- Lack of power: spark plugs, coils, fuel supply, injectors, sensors, ECU faults, cooling, or propulsion unit may be involved. This 150 HP configuration is naturally aspirated: do not search for supercharger issues as you would with a supercharged engine.
- Fault code display: the code points to a detected anomaly, without necessarily identifying a faulty part. Verify the error code and associated inspection procedures for the engine installed.
- Engine overheating: check water supply, cooling system, hoses, obstructions, and exhaust per documentation. Stop the engine in case of persistent warnings. Consult our article on engine overheating.
- Engine runs but thrust decreases: intake blockage, debris, internal impeller damage, or a worn wear ring may be the cause. Stop the engine and prevent restart before any inspection; never attempt to clear the intake while the engine is running.
Consult our Rotax fault code guide to assist with your inspections. (FMT)
How to identify the correct part for your SportJet 435 Sport 1503?
Please send us a clear photo, the visible OEM part number, the model, year, and engine serial number. Specify that it is the Rotax 1503 150 HP engine and confirm the presence of the iNR option for relevant components. Do not rely solely on the "SportJet 435" designation.
Identify my part from a photo.
SportJet 435 Sport Rotax 1503 or Standard Rotax ACE 903?
The two configurations compared below have a 7-person capacity and a 60-liter tank, but their engines and performance differ. Data concerns the versions described and may vary by model year and equipment.
| Feature | 435 Sport – Rotax 1503 | 435 Standard – Rotax ACE 903 |
|---|---|---|
| Length | 4.35 m | 4.35 m |
| Width | 1.94 m | 1.94 m |
| Height | 1.06 m | 1.06 m |
| Dry weight | 480 kg | 446 kg |
| Engine | BRP Rotax 1503 4-TEC | BRP Rotax ACE 903 |
| Power | 150 HP | 90 HP |
| Capacity | 7 people | 7 people |
| Tank | 60 liters | 60 liters |
| Top speed (claimed) | 84 km/h (52 mph) | 64 km/h (40 mph) |
| Recommended yacht | Approx. 20 m and up | 20 m and up |
The 150 HP Sport 1503 offers superior acceleration and top speed, which is particularly attractive for water sports. The 90 HP Standard ACE 903 remains another configuration of the same model, with its own parts and features. Consult our Williams SportJet 435 Standard guide.
WILLIAMS 435 SportJet (Rotax 1503): Frequently Asked Questions - FAQ
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Which engine powers the Williams SportJet 435 Sport?
This generation of the SportJet 435 Sport is equipped with the BRP Rotax 1503 4-TEC, a 1,494 cc four-stroke three-cylinder engine developing 150 HP.
-
What is the difference between the SportJet 435 Standard and the SportJet 435 Sport?
The Standard version of this generation uses the 90 HP Rotax ACE 903, while the Sport version described uses the 150 HP Rotax 1503. The Sport version offers significantly higher acceleration and top speed.
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What is the top speed of the SportJet 435 Sport 1503?
The announced top speed for the 150 HP version can reach approximately 84 km/h (52 mph), depending on the configuration and operating conditions.
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What is the displacement of the Rotax 1503?
The Rotax 1503 described has a displacement of 1,494 cc and a four-stroke three-cylinder architecture.
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How many people can the SportJet 435 carry?
The Williams SportJet 435 described can carry up to 7 people. Observe your tender's capacity and load limits.
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What is the fuel tank capacity?
The fuel tank capacity of the SportJet 435 Sport is 60 liters.
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What is the weight of the SportJet 435 Sport 1503?
The dry weight indicated for this version is approximately 480 kg, with potential variations depending on the year and equipment.
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Is the SportJet 435 Sport 1503 equipped with a supercharger?
No. In this Williams 150 HP configuration, the Rotax 1503 is a naturally aspirated version.
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Which spark plugs should be used for a SportJet 435 Rotax 1503?
The recommended spark plugs are NGK DCPR8E. Our adaptable DCPR8E compatible spark plug is perfectly suited for the Williams 435 Sport with a 1503 engine. Note: Do not confuse it with the CR8EB for the Standard ACE 903.
- When should I perform an oil change on the Rotax 1503?First service after break-in: to be performed between 10 and 25 hours (oil change and oil filter replacement, checks of hoses, clamps, and general inspection). The maintenance schedule (see above) subsequently requires the replacement of engine oil and oil filter at 50 hours or 1 year, then every 100 hours or 1 year thereafter. Also, consult the corresponding user manual.
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When should the spark plugs be replaced?
The provided schedule calls for inspection at the 50-hour and 100-hour intervals, and then replacement at 200 hours or 2 years.
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Should the SportJet 435 be flushed after use in the sea?
Yes. It is imperative to perform a flush after use in saltwater or polluted water. Anti-corrosion protection is particularly important in a marine environment. Follow the WILLIAMS and Rotax procedure; consult our flushing guide in addition to the manual.
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Why does my SportJet 435 1503 lack power?
A loss of power may stem from the following elements:
- spark plugs or ignition coils;
- fuel supply;
- injectors;
- engine sensor;
- fault code recorded in the ECU;
- obstruction of the water intake;
- jet pump or wear ring;
- cooling system issue.
Reading fault codes and methodical diagnostics are recommended before replacing parts. (FMT)
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Where can I find parts for a Williams SportJet 435 Rotax 1503?
Rotax Tender Parts offers maintenance parts and components whose applications are specified in the product sheets. Browse the table in this article and our Rotax parts catalog, then verify the part number and engine model for each product. If you do not know the part number, send us a photo, the year, and engine information via Identify your part.
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