WILLIAMS 520 SportJet
(Rotax 1503 Engine)
Technical Guide, Maintenance and Spare Parts
The Williams SportJet 520 is a jet-propelled sport tender equipped, on this generation, with the BRP Rotax 1503 4-TEC 200 HP engine, a four-stroke three-cylinder engine with a capacity of 1,494 cm³. With its length of 5.20 meters, its capacity for 7 people and its 100-liter fuel tank, it is designed for travel as a yacht tender and for water activities. The indicated top speed for this version is 84 km/h (52 mph).
At Rotax Tender Parts, we offer maintenance and replacement parts for the SportJet 520 and Rotax engines: filters, spark plugs, sensors, relays, fuel systems, gaskets, and propulsion block components.
Find Parts for Your WILLIAMS SportJet 520 – Rotax 1503
- Engine parts
- Fuel system
- Ignition
- Sensors
- Electrical parts
- Cooling
- Oil and filters
- Gaskets and seals
- Turbine block parts
- Other
Technical Specifications of the Williams SportJet 520 – Rotax 1503
- Overall length: 5.20 m.
- Width: 2.01 m.
- Height: 1.40 m.
- Draft under load: 0.42 m.
- Dry weight: 595 kg.
- Engine: BRP Rotax 1503 4-TEC, three-cylinder, four-stroke.
- Displacement: 1,494 cm³.
- Power: 200 HP.
- Propulsion: jet.
- Top speed: 84 km/h (52 mph).
- Capacity: 7 people.
- Fuel tank: 100 liters.
- Maximum load: 750 kg.
- Tube compartments: 5.
- CE category: C.
- Fuel: unleaded gasoline.
Specifications may vary slightly depending on the year of manufacture and the tender configuration. For engine part identification, it is recommended to check the Rotax 1503 serial number.
Maintenance Schedule – Williams SportJet 520
The Williams SportJet 520 maintenance program distinguishes checks to be performed at each use, after the break-in period, at regular intervals, and at the end of the season.
For all operations specific to the Rotax 1503 engine, the recommendations of the Rotax engine manual must also be followed.
| Item | At each use | 10-hour break-in | Every 60 hours | End of season |
|---|---|---|---|---|
| Turbine block / propulsion block | Inspect | ✓ | ✓ | — |
| Propulsion block anodes | Inspect / replace if necessary | ✓ | ✓ | ✓ |
| Carbon ring and shaft bellows | Dealer check every 100 hours or before the season | — | — | — |
| Bilge | Inspect / clean | ✓ | — | ✓ |
| Electrical connections | Inspect / clean / lubricate | ✓ | — | ✓ |
| Fuel circuit | Inspect | ✓ | — | ✓ |
| Ignition / battery disconnect | Inspect / clean / lubricate | ✓ | ✓ | ✓ |
| Reverse cable | Inspect / clean / lubricate | ✓ | ✓ | ✓ |
| Steering cable | Inspect / clean / lubricate | ✓ | ✓ | ✓ |
Routine maintenance recommended by Williams
In addition to the periodic schedule, Williams recommends in particular to:
- wash the tender regularly with fresh water to remove salt deposits;
- check the engine oil level;
- check the coolant level;
- flush the open cooling circuit;
- grease the control cables on the console side and the propulsion block side;
- check for water, oil, or fuel in the bilge;
- regularly check the condition of the anodes;
- regularly check the tube pressure.
After use in salt water
After use at sea, rinsing is particularly important. It is advisable to:
- rinse the tender with fresh water;
- perform the engine flushing procedure;
- rinse the turbine block and the propulsion area;
- check the intake screen;
- check the condition of the anodes;
- inspect the engine compartment;
- monitor electrical connections and any signs of corrosion.
Intensive use or use in a tropical environment may require more frequent maintenance intervals. Follow the procedure in your manual; consult our engine flushing guide as a supplement.
Common parts of the WILLIAMS SportJet 520 – Rotax 1503
This selection (except the yellow wear ring, specific to the 520 assembly) applies to the Williams SportJet 400, 460, and 520 range equipped with the Rotax 1503 engine. OEM references identify the replaced parts; they do not automatically designate original parts. Click on a "Buy" thumbnail to add one unit of the product to the cart and access the cart. If the version or batch requires a choice, the "Choose the version" thumbnail opens the product sheet. The names and references retain their links to the sheets.
iNR components concern only the tenders equipped with this option; the engine overhaul parts on the second table require specific validation for the installed engine configuration.
| Buy | Part | OEM Reference | Function |
|---|---|---|---|
 |
1503 4-TEC Head Gasket | 420641110 / 420950770 | Block sealing. |
 |
Cylinder head cover gasket | 290950820 / 420950820 | Cylinder head cover seal. |
 |
4-TEC Timing Chain | 420898042 | Timing chain. |
 |
1503 Oil Pump Bellows | 420832648 | Shaft seal (transmission) |
 |
1503 Connecting Rod Bearing Kit | Unspecified | Lower engine rebuild. |
 |
1503 Intake / Exhaust Valve | 420254682 ; 420254293 / 420254298 | Targeted replacement; compare intake or exhaust, dimensions, ports, and keys. |
 |
1503 Valve Stem Seals | 420630200 / 420630202 | Valve stem sealing; set of 6 or 12 depending on the variant. |
 |
1503 4-TEC Magneto Stator | 420889721 / 420889720 / 290889720 | Electrical generation. |
 |
1503 Complete Engine Gasket Kit | Unspecified | Gasket set for an engine rebuild |
 |
4-TEC Forged Connecting Rod | 420917516 | Piston stroke transmission. |
 |
Connecting Rod and Crankshaft Bearings | 420933456 / 420933466 / 420933523 | Lower engine rebuild. |
 |
Intake Air Temperature Sensor | 420222427 / 420222423 | Air temperature measurement. |
Common Problems with the WILLIAMS SportJet 520 – Rotax 1503
The following symptoms can have several causes. These clues help guide checks, but do not replace a diagnosis or automatically justify replacing a part. Work on fuel, electrical systems, and moving parts must comply with the manual and be entrusted to a professional when necessary. (FMT)
- The engine does not start: battery, cranking voltage, battery disconnect, safety kill switch, fuses, relays, fuel supply, spark plugs, coils, injectors, or sensors may be affected.
- Engine misfires: methodically check the ignition, fuel supply, sensors, wiring, and compression before replacing a part.
- Lack of power: injection, ignition, cooling, electronic limitation, or propulsion unit may be to blame. A clogged water intake, damaged turbine, or excessive play can reduce thrust.
- Fault code displayed: the code identifies a detected anomaly, but does not prove on its own that a part needs to be replaced.
To guide your checks, consult our list of Williams and Rotax fault codes and our Rotax fault code guide. Stop the engine and prevent it from restarting before inspecting the water intake or propulsion unit.
How to identify the right part for your SportJet 520?
Send us a clear photo, the visible OEM part number, the model, the year, the HIN, and the engine serial number. Specify the Rotax 1503 engine, its horsepower, and the presence of the iNR option for the components concerned. Do not rely solely on the SportJet 520 designation.
Identify my part from a photo.
WILLIAMS SportJet 520 Rotax 1503: Frequently Asked Questions - FAQ
-
What engine is fitted to the Williams SportJet 520?
The SportJet 520 of this generation uses a BRP Rotax 4-TEC from the 1503 family, a three-cylinder four-stroke engine with 1,494 cm³. Williams rates this version at 200 HP in its owner's manual.
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Does the SportJet 520 have the same Rotax 1503 as other Williams?
The Rotax 1503 has been used in different configurations and power ratings on several Williams Jet Tenders. The differences in power from one boat to another result from ECU / ECM programming and different propulsion units.
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What is the maximum speed of the Williams SportJet 520?
Williams rates it at approximately 84 km/h (52 mph). The actual speed may vary depending on the load, hull condition, operating conditions, and propulsion condition.
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What is the weight of the SportJet 520?
Williams states a dry weight of 595 kg.
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How many people can the SportJet 520 carry?
The SportJet 520 is designed for 7 people..
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What is the tank capacity?
The SportJet 520 has a tank of approximately 100 liters.
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Why won't my Williams SportJet 520 start?
The first elements to check include:
- battery and cranking voltage;
- battery disconnect;
- safety kill switch;
- fuses and relays;
- fuel pump;
- fuel pressure;
- spark plugs;
- ignition coils;
- injectors;
- engine sensors;
- fault codes recorded by the ECU.
An electronic diagnosis can prevent the unnecessary replacement of several components. (FMT)
-
Why does my Rotax 1503 start but lack power?
A loss of power may be related to the engine or the propulsion. The main clues are:
- spark plugs or coils;
- fuel supply;
- injectors;
- engine sensor;
- cooling problem;
- electronic limitation related to a fault;
- clogged water intake;
- damaged turbine;
- excessive play in the propulsion unit.
It is important to inspect the propulsion unit before concluding that there is an engine problem. Stop the engine and prevent it from restarting before this inspection.
-
Why is my SportJet 520 overheating?
Overheating can notably be caused by:
- obstruction of the water circuit;
- clogged water intake;
- improper rinsing;
- damaged or clogged hose;
- cooling problem;
- defective temperature sensor.
If a temperature alarm appears, avoid continuing to use the engine before identifying the cause. See our article on engine overheating.
-
Should the SportJet 520 be rinsed after every outing at sea?
Yes. Rinsing with fresh water is particularly important after use in salt water. Williams recommends rinsing the open cooling circuit and regularly cleaning the tender to remove salt deposits. Follow the applicable manual procedure; our engine rinsing guide is complete without replacing it.
-
What is the carbon ring of the SportJet 520?
The carbon ring (or carbon ring, or carbon ring) is part of the transmission shaft sealing system. Its condition and that of the rubber bellows must be monitored. Williams recommends a professional check every 100 hours or before the season. An anomaly in this system can notably cause water to enter the engine compartment.
-
Why is there water in the bilge of my SportJet 520?
A small amount of water can have different origins, but an abnormal accumulation must be investigated. In particular, it is advisable to check:
- shaft sealing system (carbon ring, bellows...);
- seawater / coolant heat exchanger (Plate heat exchanger)
- hoses;
- fittings;
- exhaust system;
- bilge pump
- hole or crack in the hull.
The presence of water must be diagnosed quickly if it reappears after each use.
-
Why does my SportJet 520 cavitate on acceleration?
A sensation of cavitation or loss of thrust on acceleration may be due to:
- debris in the intake screen;
- a damaged propeller;
- a damaged propulsion unit
- incorrect clearance between the turbine and its surroundings;
- deterioration of propulsion unit components (see our article on wear rings);
- air intake or water flow disturbance.
The propulsion system should be inspected before looking for an engine failure. Stop the engine and prevent it from restarting before inspecting the screen and turbine housing.
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What oil should I use in the SportJet 520 Rotax 1503?
Use oil that meets the specifications recommended by BRP for this engine: XPS 4T 5W-40.
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Which spark plugs should I use on the SportJet 520?
The recommended spark plugs are NGK DCPR8E. Our DCPR8E compatible spark plug is perfectly suited for the Williams 520 Sport with a 1503 engine.
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How can I identify the correct fuel pump, relay, or sensor?
Do not rely solely on the "SportJet 520" label. To correctly identify a part, use the following whenever possible:
- the tender's year;
- the HIN number;
- the engine serial number;
- the part number marked on the original part;
- a photo of the part.
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Where can I find parts for a Williams SportJet 520 Rotax 1503?
Rotax Tender Parts offers engine parts and components for Rotax 1503 engines, notably used on Williams Jet Tenders. Find the selection in the tables in this article and consult our Rotax parts catalog. .
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