SIERRA 18-8906 Impeller Johnson/evinrude

( Brand: Sierra ), ( Manufacturer Part Number: 18-8906 ), ( Part Type: Impeller )

Review SIERRA Replacement Impeller Johnson/evinrude

The **Sierra 18-8906 Impeller** is a high-performance, precision-engineered replacement part designed specifically for Johnson and Evinrude outboard motors, ensuring optimal water flow, enhanced throttle response, and extended engine longevity. Crafted from durable, corrosion-resistant materials, this impeller is built to withstand the demanding conditions of marine environments, including saltwater exposure, high RPMs, and prolonged use. Its unique design features a carefully balanced blade configuration, which maximizes water displacement while minimizing turbulence, allowing the engine to operate at peak efficiency. The impeller s tight tolerances and smooth machining reduce friction and wear on the engine s internal components, such as the lower unit and drive shaft, thereby reducing the risk of costly repairs and improving overall reliability. Whether installed on a recreational boat, a fishing vessel, or a performance watercraft, this impeller delivers superior power transfer and fuel economy, making it an essential upgrade for any marine enthusiast seeking to restore or enhance their Johnson or Evinrude outboard s performance. Backed by Sierra s reputation for quality and compatibility, this impeller is a direct-fit solution that ensures seamless installation and immediate performance benefits, helping to keep your engine running smoothly for years to come.

**Pros and Cons of buying a Sierra 18-8906 Impeller for Johnson/Evinrude Engines**

The Sierra 18-8906 impeller is a popular aftermarket replacement for stock Johnson and Evinrude outboard motors, particularly in models with 90-degree V-twin engines. Below is a detailed breakdown of its advantages and drawbacks.

### **Pros**

1. **Improved Performance and Throttle Response**

The Sierra 8906 impeller is designed to increase water flow through the engine, which enhances throttle response and power delivery. Many users report a noticeable difference in acceleration, especially in the mid-range RPMs. This is particularly beneficial for fishing boats where quick bursts of speed are needed.

2. **Better Fuel Efficiency**

By optimizing water flow, the impeller helps the engine run more efficiently, reducing fuel consumption. This can be especially useful for long days on the water where fuel economy matters.

3. **Reduced Heat and Stress on the Engine**

Improved water circulation helps cool the engine more effectively, reducing the risk of overheating. This can extend the life of critical components like the lower unit and water pump.

4. **Compatibility with Stock Lower Units**

The Sierra 8906 is designed to fit standard Johnson/Evinrude lower units without requiring modifications. This makes it a straightforward upgrade for most owners.

5. **Durability and Quality Materials**

Sierra impellers are made from high-quality materials, including reinforced nylon or composite blends, which are more durable than some stock impellers. They are also resistant to warping and cracking over time.

6. **Easier Installation**

Unlike some high-performance impellers that require lower unit modifications, the Sierra 8906 can often be installed with basic tools and minimal effort. Many users report being able to complete the job in under an hour.

7. **Cost-Effective Upgrade**

Compared to full engine upgrades or high-end performance kits, the Sierra 8906 is relatively affordable. It provides noticeable performance gains without the expense of a complete overhaul.

8. **Reduced Cavitation and Vibration**

A well-designed impeller like the Sierra 8906 helps minimize cavitation (air bubbles forming in the water pump), which can cause vibration and damage to the engine over time.

---

### **Cons**

1. **Potential for Increased Wear on Lower Unit Components**

While the Sierra 8906 is designed to be compatible, some users report increased wear on the lower unit s water pump seals or bearings over time. This is due to the higher water flow and pressure generated by the impeller. Regular maintenance and seal checks are recommended.

2. **Possible Voiding of Warranty**

Many manufacturers void warranties if aftermarket impellers are installed. Johnson/Evinrude, for example, may not cover engine issues if an impeller upgrade is detected. Owners should check their warranty terms before proceeding.

3. **Mixed Reviews on Long-Term Durability**

Some users report that while the Sierra 8906 holds up well initially, it may not last as long as stock impellers in extreme conditions (e.g., frequent deep-diving, heavy loads, or saltwater use without proper flushing). Saltwater environments can accelerate wear on plastic impellers.

4. **Not a Substitute for Full Engine Tuning**

While the Sierra 8906 improves performance, it is not a replacement for a full engine tune-up, carburetor adjustment, or exhaust system modifications. For maximum gains, these should be addressed alongside the impeller upgrade.

5. **Potential for Increased Noise**

Some owners notice a slight increase in engine noise, particularly at higher RPMs, due to the impeller s design. This is usually minor but may be noticeable in quiet conditions.

6. **Limited Effect on Top-End Power**

The Sierra 8906 is optimized for mid-range performance and throttle response rather than raw top-end horsepower. For significant horsepower gains, a full performance kit (including a larger impeller, exhaust, and carburetor) would be required.

7. **Installation Risks if Not Done Correctly**

Improper installation such as misalignment or incorrect torque on bolts can lead to leaks or impeller failure. While the upgrade is straightforward, inexperienced DIYers may encounter issues if they lack familiarity with outboard maintenance.

---

### **Conclusion**

The Sierra 18-8906 impeller is a solid aftermarket choice for Johnson/Evinrude owners looking to enhance throttle response, fuel efficiency, and cooling without a major investment. It strikes a balance between performance gains and practicality, making it suitable for recreational and light fishing applications. However, it is not a universal fix for all engine issues and may require additional maintenance to prevent long-term wear.

For owners who prioritize **improved mid-range power, better cooling, and a cost-effective upgrade**, the Sierra 8906 is a worthwhile consideration. Those who plan to push their engines to extreme limits (e.g., high-speed planing, heavy loads, or frequent deep-diving) may need to pair it with other modifications or opt for a more robust impeller.

---

### **Recommendation**

- You want noticeable improvements in throttle response and fuel efficiency without a full engine overhaul.

- Your primary use is fishing, cruising, or light recreational boating.

- You are comfortable performing basic maintenance and checking seals periodically.

- You are willing to accept that it may not drastically increase top-end power or last indefinitely in harsh conditions.

- You rely on warranty coverage for your engine and are unwilling to risk voiding it.

- You plan to use the boat for high-performance activities (e.g., racing, heavy towing, or extreme deep-diving).

- You prefer a more aggressive performance upgrade and are open to full engine tuning kits.

- You are unsure about installation or maintenance and lack experience with outboard repairs.

**Final Verdict:** The Sierra 8906 is a **good mid-tier upgrade** for most Johnson/Evinrude owners seeking practical performance gains. For those who want maximum power, a full performance kit (including a larger impeller, exhaust, and carburetor) would be more appropriate. Always ensure compatibility with your specific engine model and follow installation guidelines carefully.

Details:

The impeller fits Johnson/Evinrude OMC/BRP outboard model's: 5HP 1996-98 and 6-8HP 1991-2005. Sierras 18-8906 Impeller replaces Johnson/Evinrude OMC/BRP Part Number 436137. This platform is now integrated and seamless.

part #: 188906 prices

• $30.71-$79.22

specifications ignitionstartin:

• for makes: Johnson, Evinrude
• brand: Sierra
• mpn: 18-8906
• part type: Impeller

general ignitionstartin:

• Boat Parts > Inboard Engines Components > Ignition Starting Systems
• condition: New

offer ignitionstartin:

• availability: In Stock
• started: June 7, 2026
• sold: 0
• quantity: 1
• options: Ship-to-home

shipping ignitionstartin:

• transit: 4-10 Days
• service: Economy
• type: Fixed
• cost: $0.00
• class: Economy

seller ignitionstartin:

• # reviews: 113178
• city: Wheeling, Illinois
• rating: 99.0%

payments ignitionstartin:

• other
• wallet: Paypal
• credit card: Mastercard

returns ignitionstartin:

• policy: Returns Accepted
• time: 30 Days
• paid by: Seller

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