When to change NGK CR8EB spark plugs on your Williams or Seadoo Spark?

April 22, 2026

Quand changer les bougies NGK CR8EB sur votre Williams ou Seadoo Spark ?

Why are spark plugs essential for a Rotax ACE engine?

Spark plugs are at the heart of your Rotax ACE engine's combustion process. They generate the spark that ignites the air/fuel mixture during each engine cycle. For Rotax ACE 903 engines, found in Sea-Doo Spark and WILLIAMS tenders (Sportjet, Turbojet, Minijet), the recommended spark plug is the NGK CR8EB. Worn or fouled spark plugs lead to misfires, increased fuel consumption, and a significant loss of power.

When to change NGK CR8EB spark plugs?

BRP recommends replacing spark plugs at the following intervals:

Every 100 hours of navigation or every 2 years, whichever comes first
Systematically during each spring recommissioning if the spark plugs are more than one season old
Immediately in case of failure symptoms (see below)

On a Rotax ACE 903 engine (Sea-Doo Spark, WILLIAMS Minijet), there are 3 spark plugs to replace. On ACE 1503 and 1603 engines (WILLIAMS Sportjet, Turbojet), you will also need 3 spark plugs but of type DCPR8E. Always replace them as a complete set to ensure consistent combustion.

Symptoms of a faulty spark plug

Difficulty starting or engine stalling at idle
Noticeable misfires (abnormal vibrations)
Loss of power or sluggish acceleration
Unexplained increase in fuel consumption
Check engine light on (fault code related to ignition)
Smell of unburnt fuel from the exhaust

How to inspect NGK CR8EB spark plugs?

Regular visual inspection allows you to assess the condition of the engine and the spark plug:

Light brown/greyish electrode: normal combustion, spark plug in good condition
Black and dry deposits: too rich mixture or clogged air filter
Black and oily deposits: oil in the combustion chamber, engine wear
White or melted electrode: overheating, cooling problem, or unsuitable fuel
Eroded or rounded electrode: spark plug at the end of its life, immediate replacement

Also check the electrode gap: it should be between 0.7 and 0.8 mm for Rotax ACE engines. A gap outside tolerance degrades ignition performance.

How to replace NGK CR8EB spark plugs?

Required materials

3 NGK CR8EB spark plugs (set of 3 recommended)
Appropriate spark plug wrench (16 mm)
Torque wrench
Clean rags
Penetrating oil spray (if spark plugs are stuck)

Replacement steps

Step 1 — Access the spark plugs
Open the engine hood. On Sea-Doo Spark and WILLIAMS, the spark plugs are accessible on top of the Rotax ACE engine block (903, 1503, and 1603). Disconnect the ignition coils by pulling on the boot (never on the cable).

Step 2 — Remove the old spark plugs
Unscrew the spark plugs with the spark plug wrench counter-clockwise. If they are stuck, apply penetrating oil and wait a few minutes before forcing. Clean the spark plug housing before installing the new ones.

Step 3 — Install the new spark plugs
Screw the new NGK CR8EB spark plugs in by hand until contact, then tighten with a torque wrench: 20 to 25 Nm. Do not overtighten to avoid damaging the cylinder head threads.

Step 4 — Reconnect and test
Reconnect the spark plug wires, ensuring they click into place correctly. Start the engine and check for misfires. The engine should run smoothly and evenly.

Why choose the NGK CR8EB?

The NGK CR8EB is the original spark plug recommended by BRP for Rotax ACE engines. It offers:

Built-in resistance (5 kΩ) to reduce electromagnetic interference
A thermal index of 8 suitable for high-stress marine engines
Proven reliability on Rotax ACE engines in marine conditions
Guaranteed compatibility with BRP ignition systems

Do not use spark plugs with a different thermal index without manufacturer validation: a spark plug that is too cold will foul quickly, a spark plug that is too hot risks causing destructive pre-ignition.