Rotax 903 ACE Engine

for SEADOO and WILLIAMS jet-propelled tenders

The Rotax ACE 903 engine (often called Rotax 900 ACE) is a 4-stroke inline 3-cylinder internal combustion engine designed by BRP-Rotax, known for its light weight, low fuel consumption, and reliability. It powers certain Sea-Doo jet skis and the majority of WILLIAMS jet-propelled tenders. At Rotax Tender Parts, we offer maintenance and replacement parts for these applications: oil filters, spark plugs, sensors, and transmission parts. Check the model, year, and use the original OEM reference to find its compatible equivalent.

Find parts for your Rotax 903 ACE engine

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

Which models use the Rotax 903 ACE engine?

WILLIAMS Tenders:

• Since 2016: WILLIAMS 280 Minijet.
• Since 2017: WILLIAMS 345 Sportjet
• Since 2017: WILLIAMS 395 Sportjet
• Since 2017: WILLIAMS 435 Sportjet (standard version)
• Since 2019: WILLIAMS 285 Turbojet,
• Since 2019: WILLIAMS 325 Turbojet

SEADOO Jet Skis:

• 2014–2026: Spark 2UP / 3UP and TRIXX
• 2014–2015: Spark 903, 2UP / 3UP versions
• 2016: Spark 2UP HO 900 ACE; Spark 2UP iBR 900 HO ACE; Spark 3UP iBR 900 HO ACE,
• 2017: Spark 903 and 903 HO, 2UP / 3UP / iBR versions; Spark TRIXX.
• 2018: Spark P-1 60 hp, P-1 90 hp, P-1 iBR 90 hp, P-2 90 hp and P-2 iBR 90 hp.
• 2019–2020: Spark DT NA / TRIXX 2900,
• 2017: GTI 903; GTI SE 903; GTS 903,
• 2018–2020: GTI 90.
• 2017–2026: GTS equipped with the Rotax 900 / 903 ACE, (continuity of versions to be confirmed)
• 2018: GTS 90,

Check the installed engine, year, and OEM part number before ordering.

Common parts for the Rotax 903 ACE

Select a product below to open its details page. This list brings together parts, accessories, and tools whose descriptions mention the Sea-Doo Spark, Williams 280 Minijet or Turbojet 285 / 325 (from 2019 only), or the Williams Sportjet 345, 395, and 435 (Std). Confirm the year, reference, dimensions, and fitment before ordering.

Common Rotax 903 ACE problems

The symptoms below may involve multiple components or systems. These are potential causes, not a diagnosis or troubleshooting guide. A symptom is not sufficient to identify a part to replace.

• Engine does not start: have the battery, starting circuit, power supply, wiring, connectors, fuel supply, and ignition checked according to the model procedure.
• Engine misfire: checks may include spark plugs, ignition, injection, fuel, sensors, wiring, and compression.
• Lack of power: distinguish between an engine fault and a propulsion unit problem. Intake, fuel supply, ignition, compression, turbine, and wear ring should be evaluated according to the installed configuration.
• Displaying a fault code: record the exact code and the circumstances under which it appeared. A code may relate to a circuit, a power supply, or a signal; it does not by itself confirm that a sensor is faulty.

To learn more about fault codes, consult our complete list of Rotax fault codes for Sea-Doo and Williams and our guide for decoding Rotax fault codes on Sea-Doo and Williams. Verify that the information consulted applies to your model.

How to identify the correct ROTAX Ace 903 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. Include the model year and, if available, the engine identification number. We can help you identify the appropriate replacement part.

You can also use our automatic part recognition tool for the item you are looking for by clicking:

Identify my part from a photo

Rotax 903: Frequently Asked Questions - FAQ

• What is the Rotax 903 ACE engine?

  The engine designated as Rotax 903 ACE or 900 ACE in our catalog is used on certain Sea-Doo personal watercraft and Williams jet-propelled tenders. Check if your machine is included using the detailed list above.

• Where to find the Rotax engine serial number?

  On the Rotax 903 ACE engine, the serial number, generally composed of 8 digits, is located on a plate attached to the intake manifold.

   
• Are Sea-Doo Rotax 903 ACE parts compatible with Williams tenders?

  All parts relating to the engine block are identical for Jet Skis (personal watercraft) and WILLIAMS tenders. However, check the elements specific to marinization (notably the exhaust system, which is equipped with a catalytic converter on tenders), the transmission (driveshaft, carbon seal, stuffing box...), and the propulsion unit.

• Which Sea-Doo models use the Rotax 903 ACE engine?

  All SEADOO Spark, Spark TRIXX, GTI / GTI SE 903, GTI 90 and GTS 903 / 90. Consult the models and model years above and then the compatibility of each part; this list is not exhaustive.

• Which Williams tender models use the Rotax 903 ACE engine?

  The 280 Minijet, 285 / 325 Turbojet since 2019 and 345 / 395 / 435 Sportjet Std are equipped with the Rotax ACE 903. Consult the detailed list above.

• Should the information for supercharged Rotax versions be applied to the Rotax 903 ACE?

  No: the supercharger and overhaul indications for the 1503 guide do not apply to the 903 ACE because it does not exist in a supercharged version (no turbo or supercharger). All Rotax 903 engines are "naturally aspirated".

• Which engine oil should be used in a Rotax 903 ACE?

  Generally, BRP XPS 4T 5W-40 synthetic oil. This oil is the same for the Rotax 1503 and the Rotax 1630.

• How much oil is required in a Rotax 903 ACE engine?

  Approximately 3.4 to 3.6 liters depending on the exact configuration of the crankcase. Note that, during an oil change, not all the oil can be removed, as some remains inaccessible at the bottom of the crankcase. Generally, the volume of oil that can be replaced during an oil change is between 2 and 3 liters.

• How to correctly check the oil level of a Rotax 903 ACE?
  • Start the engine and run it with an appropriate water supply if it is out of the water, or navigate 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 fluidity and circulation.
  • Immediately stop the engine using the start/stop button or remove the safety lanyard.
  • Wait approximately 30 to 60 seconds to allow the oil to drain back into the reservoir/oil pan.
    
  • Top up gradually only if necessary, then recheck the level using the same procedure.
    
    
• Which oil filter is suitable for the Rotax 903 ACE engine?

  Our catalog offers the 420956123 for Sea-Doo personal watercraft and Williams tenders powered by the ACE 903. 

• Which spark plugs are used on a Rotax 903 ACE?

  The recommended spark plugs are NGK CR8EB spark plugs. Rotaxtenderparts.com offers generic compatible NGK CR8EB spark plugs, Rotax reference 5297925, in packs of 3.

• How often should a Rotax 903 ACE engine be serviced?

  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). Regular full maintenance: every 50 hours or once a year.

• Why won't my Rotax 903 ACE engine start?

  Several systems may be involved: battery, electrical supply circuit, fuel (fuel pump), or ignition. Note the symptoms and any fault codes before having the engine checked.

• Why does my Rotax 903 ACE start but lose power during acceleration?

  An inspection must distinguish between supply, ignition, intake, or compression problems and issues with the propulsion unit. Indeed, a foreign object stuck in the propulsion unit will affect the power of your machine without affecting engine performance. This symptom alone, therefore, does not allow for determining which part to replace.

• Why is my Rotax 903 ACE engine overheating?

  Possible causes may be a loss or poor circulation of coolant, a faulty thermostat (not opening correctly), insufficient raw water flow (clogged exhaust cooling circuit, pinched hose, suction of seaweed or other debris, towing valve closed where applicable...), or heat exchanger problems. Consult our article dedicated to overheating, which provides general leads to check for your model.

• Why does my Rotax 903 ACE run irregularly or misfire?

  The diagnosis may focus on spark plugs, ignition, injection, fuel, sensors, wiring, or compression. 

• What are the problems that can affect the Rotax 903 ACE engine?

  Starting difficulties, misfiring, loss of power, overheating, or electrical faults are possible symptoms. Frequent oxidation of electrical harnesses and a bad ground on the engine block have been documented, among others. This presentation does not constitute a ranking of their frequency on the 903 ACE.

• How to read Rotax 903 ACE fault codes?

  Follow the procedure on your model's display or use a compatible diagnostic tool. Consult our fault code guide, verifying its applicability to your installation.

• What do the Rotax 903 ACE fault codes mean?

  They indicate detected anomalies, not necessarily a faulty part. Consult our Rotax fault code list, then the model documentation to confirm their interpretation.

• How to know if a Rotax 903 ACE fuel pump or injector is faulty?

  Fuel pump: check the 12V supply, listen if a brief humming sound is heard for 2 to 3 seconds (pressurization), and check the fuel pump pressure (minimum 56 psi). Injectors: disconnect them electrically one at a time, or carefully remove them from the engine to observe if they spray when the engine is turned on. Caution: these operations must be performed with all necessary precautions.

• How to identify the right spare part for my Rotax 903 ACE engine?Verify the OEM reference, engine version, model, and year, or send us a photo, or use our visual recognition tool integrated into this site. It's simple and fast: take a picture of your part, and if we have that part, you will be immediately directed to the relevant product page.
  
  
• Where to buy replacement parts for Rotax 903 ACE?

  Consult the product pages in the table above at Rotax Tender Parts for the suggested replacement parts, or a brand dealer for original parts. Always confirm the compatibility and nature of the product before ordering.