Rotax 1503 engine

October 14, 2026

Rotax 1503 4-TEC Engine

for SEADOO and WILLIAMS jet-powered tenders

The Rotax 4-TEC 1503 is a 3-cylinder, 4-stroke engine recognized for its reliability and efficiency in high-end marine propulsion. At Rotax Tender Parts, we offer a wide range of maintenance and replacement parts compatible with OEM references for SEADOO jet skis and WILLIAMS tenders equipped with the Rotax 1503 engine (as well as 1630 and 903 models). From seals and sensors to pumps and pistons, our aftermarket parts are selected to ensure optimal performance and long-term durability for your engine at the best price.

Find parts for your Rotax 1503 engine

Engine parts
Fuel system
Ignition
Sensors
Electrical parts
Cooling
Oil and filters
Gaskets and seals
Jet pump parts
Other

Which models use the Rotax 1503 engine?

WILLIAMS tenders:

2015–2021: WILLIAMS 435 Sportjet (Sport version)
2015–2021: WILLIAMS 400 Sportjet
2015–2021: WILLIAMS 460 Sportjet
2015–2021: WILLIAMS 520 Sportjet

SEADOO Jet Skis:

2002–2006: GTX 4-TEC, including Standard, Wake, Supercharged, Limited SC, and Limited SCIC versions.
2004–2006: RXP / RXP Supercharged.
2005–2006: RXT.
2006–2007: GTI 4-TEC, including Standard, SE, and Rental versions.
2007: GTX 4-TEC Standard, Wake, and Limited BVIC; RXP 1503 BVIC and NA; RXT BVIC.
2007–2016: GTI 130; GTX 155 and GTX 215.
2008: RXP 155.
2008–2009: RXP 215; GTX Limited 215.
2008–2010: RXT 215; GTI SE 130, GTI SE 155, and GTI Rental 130.
2008–2011: RXP-X 255.
2008–2016: GTI 155.
2009: GTX Limited iS 255.
2009–2010: RXT-X 255, including the RS versions listed for these years.
2009–2016: Wake 155 and Wake Pro 215.
2010–2011: GTX iS 215.
2010–2016: RXT-X 260.
2010–2017: RXT 260; GTX Limited 260.
2011: GTS Pro 130; RXT aS X / aS XRS 260; RXT 260 RS and RXT-X 260 RS.
2011–2016: GTS 130 and GTI Limited 155.
2012–2015: RXP-X 260.
2012–2016: GTR 215 and GTX S 155.

SEADOO Sport Boats:

These applications are also listed for Rotax 1503 versions in our product descriptions. For twin-engine boats, identify each installed engine and the corresponding parts separately.

2003–2006: Sportster 4-TEC.
2005–2006: Sportster S/C 215.
2005–2012: Challenger 180, including SE and SP versions.
2006–2009: Islandia 220 / SE.
2006–2011: Utopia 205 / 205 SE.
2006–2012: Speedster 200.
2007–2012: Speedster 150; Challenger 230, including SE, SP, and Wake versions.
2010–2012: Challenger 210, including SE, SP, and Wake versions.

Common Rotax 1503 parts

Select a part or reference below to open its product page. Compatibility may depend on the engine version and installed configuration. Some of these parts may be identical across multiple engine types (1503, 1630, 903...); please refer to the specific engine to identify your parts. OEM references are provided to identify replacement parts and do not mean that every product is a genuine OEM part.

Part	OEM Reference	Function
Oil Filter	420956744	Engine oil filtration. Fits 1503 and 1630 engines.
NGK DCPR8E Spark Plug	5297630 / 707000246 / 715900637 / 296000421 / 715900642	Ignition. Fits 1503 and 1630 engines.
Ignition Coil	420666142	Spark generation
35 A / 12 V Relay, single	278002822 / 278003828	Electrical circuit switching
35 A / 12 V Relay, pack of 5	278002822 / 278003828	Electrical circuit switching
Starter Solenoid Relay	278000513 / 278002347 / 278001802 / 278001766	Starter power switching
12 V Power Relay	278003012	Power supply switching
Voltage Regulator / Rectifier	710001103 / 0460375	Battery charging and voltage regulation
Magneto Stator	420889721 / 420889720 / 290889720	Electricity generation
Fuel Pump Strainer, pack of 2	270600113	Fuel pre-filtration
Crankshaft Position Sensor	420966575 / 420966570	Crankshaft position monitoring
Oil Pressure Sensor	420856533	Oil pressure monitoring
Right Throttle Position Sensor	278002283	Throttle control monitoring
Cylinder Head Gasket	420641110 / 420950770	Cylinder head sealing
PTO / Magneto Cover Gasket	420931130	PTO cover sealing
Oil Pump Rubber Bellow	420832648	Oil pump assembly component
Intake / Exhaust Valves	420254293 / 420254298: intake; 420254682: exhaust	Intake and exhaust gas control
Valve Stem Seals, 6 or 12 pieces	420630200 / 420630202	Oil sealing around valve stems
Double Valve Spring Kit	5238180 / 0462526	Valve return
Bronze Valve Guides	5253929	Valve stem guidance
WSM Piston Kit, standard size, 1503 supercharged	420890244 / 420892735	Compression and piston assembly replacement
Rotax 1503 Piston Kit, STD / +0.5 mm options	420890244	Compression and piston assembly replacement
Complete Engine Gasket Kit	Not specified in product sheet	Engine sealing during rebuild
Connecting Rod Bearing Kit	Not specified in product sheet	Connecting rod bearing support
Inconel Intake / Exhaust Valve Kit	Not specified in product sheet	Intake and exhaust gas control
Drive Shaft, 591.5 mm	271001719	Power transmission to propulsion unit

Common Rotax 1503 issues

The symptoms below may relate to several components or systems. These are possible causes, not a diagnostic or troubleshooting guide.

Engine will not start: battery, starter relay, starter motor, power supply, wiring and connectors, fuel pump, fuel supply, or ignition components.
Engine misfiring: spark plugs, ignition coils, injectors, fuel supply, wiring, sensors, or cylinder compression.
Lack of power: injection, ignition, air intake, supercharger on supercharged versions, cylinder compression, or propulsion unit components such as the impeller and wear ring.
Fault code display: sensors, power supply, wiring, connectors, or the system identified by the code. A fault code is not sufficient to confirm that a particular part needs to be replaced.

For more information on fault codes, consult our list of Rotax fault codes for Sea-Doo and Williams and our guide for decoding Rotax fault codes on Sea-Doo and Williams.

How to identify the right ROTAX Ace 1503 part?

Not sure which Rotax part to choose? Send us a photo of the part, its OEM reference, and the model of your engine or your Williams / Sea-Doo. We can help you identify the appropriate replacement part.

Identify my part from a photo

Rotax 1503: Frequently Asked Questions - FAQ

What is the Rotax 1503 engine?
A 1,503 cc 4-stroke marine engine used on certain Sea-Doo jet skis (PWC) and Williams jet-powered tenders.
Where can I find the Rotax engine serial number?
According to the 2005 SeaDoo Rotax 1503 4-TEC workshop manual, the engine identification number (E.I.N.) is located on a plate on the front of the crankcase/engine block. It is generally a 7-digit number.
Are Sea-Doo Rotax 1503 parts compatible with Williams tenders?
Yes, engine-related parts are identical, but some differences may exist for so-called "marinized" components, such as the exhaust system (exhaust manifold, catalytic converter housing, exhaust elbow...) or the heat exchanger.
Which Sea-Doo models use the Rotax 1503 engine?
Certain versions of the GTI, GTS, GTR, GTX, RXP, RXT, Wake, and sport boats; check the list above.
Which Williams tender models use the Rotax 1503 engine?
The WILLIAMS tenders powered by the ROTAX 1503 are the Sportjet 435 (Sport), 400, 460, and 520 built between 2015 and 2021; confirm the engine installed on your tender.
What are the main differences between atmospheric (naturally aspirated) and supercharged Rotax 1503 engines?
Supercharged versions use forced induction to develop more power. This is the function of the supercharger; component compatibility and maintenance requirements differ. Indeed, a supercharger overhaul, including the replacement of the shaft and bearings, is necessary every 200 hours of operation.
What engine oil should be used in a Rotax 1503?
Generally, BRP XPS 4T 5W-40 synthetic oil.
How much oil is needed for a Rotax 1503 engine?
Total capacity when dry / after complete overhaul: 4.8 US quarts (4.5 L). Capacity during a standard oil change: approximately 3.2 US quarts (3.0 L).
How do I correctly check the oil level of a Rotax 1503?
- Start the engine and run it with an appropriate water supply if out of the water, or ride briefly to bring the oil to its normal operating temperature.
- Briefly rev the engine to approximately 4,000 to 4,500 rpm for about 15 seconds to ensure oil flow and circulation.
- Stop the engine immediately using the start/stop button or remove the safety lanyard.
- Wait about 30 to 60 seconds to allow the oil to drain back into the tank/oil pan.

Which oil filter is suitable for the Rotax 1503 engine?
Check your original filter part number; confirm the compatibility of the 420956744 with your engine before ordering.
What spark plugs are used on a Rotax 1503?
The original spark plugs are NGK DCPR8E. The compatible spark plug is available here.
How often should a Rotax 1503 engine be serviced?
First break-in service: to be performed between 10 and 25 hours (oil change and filter replacement, debris check, and system inspection). Regular full maintenance: every 50 hours or once a year.
Why won't my Rotax 1503 engine start?
Possible causes include the battery, starter circuit, electrical power, fuel supply, or ignition faults.
Why does my Rotax 1503 start but lose power during acceleration?
Fuel supply, ignition, air intake, supercharger, compression, or the propulsion unit could be at fault.
Why is my Rotax 1503 engine overheating?
Possible causes include coolant loss, restricted cooling circulation, a faulty thermostat, insufficient raw water flow (clogged exhaust cooling circuit, pinched hose, suction of seaweed or other debris, closed towing valve...), or heat exchanger issues. Consult our article dedicated to overheating.
Why is my Rotax 1503 running roughly or misfiring?
Spark plugs, coils, injectors, fuel supply, sensors, wiring, or compression could be at fault.
What are the most common problems with the Rotax 1503 engine?
Possible issues include starting difficulties, misfires, loss of power, overheating, and electrical faults; causes vary by engine.
How do I read Rotax 1503 fault codes?
Use the display procedure specific to your model (navigate through your display menu until you find the "Error Codes" menu) or a compatible diagnostic tool; check our fault code guide.
What do Rotax 1503 fault codes mean?
They identify detected faults, and not necessarily defective parts; consult our list of Rotax fault codes.
How do I know if a Rotax 1503 fuel pump or injector is defective?
Fuel pump: check the 12V power supply, listen for a brief buzzing sound for 2 to 3 seconds (pressurization), and check the fuel pump pressure (at least 42 psi, or 44 psi for a supercharged version). Injectors: disconnect them electrically one at a time, or carefully remove them from the engine to observe if they spray when the engine is cranked. Caution: these operations must be performed with all necessary precautions.
How do I identify the right spare part for my Rotax 1503 engine?
Check the OEM reference, engine version, and model; send us a photo if in doubt.
Where can I buy replacement parts for a Rotax 1503?
Buy OEM parts from your local SEADOO dealer, or browse the products featured above at Rotax Tender Parts to find certified aftermarket parts at the best price. Confirm compatibility before ordering.