MERCRUISER 0L006337-P Horizion Mpi Mag Stb Locked Gears 0L006337/P 0L006338 MAG/385HP

( Brand: Mercruiser ), ( Manufacturer Part Number: 0L006337/P ), ( Part Type: Gear ), ( Stroke: 4-stroke ), ( Engine Hp : 385 ), ( Country Of Origin: United States )

Review MERCRUISER S#0l006337/p#0l006338 Horizion Mpi Mag/385hp Stb Eng Locked Bw Gears fits 454

The **Mercruiser Horizon 454 MPI MAG/385HP STB Locked BW Gears** is a high-performance, marine-grade inboard engine designed for demanding applications in both recreational and commercial vessels, offering an exceptional blend of power, efficiency, and reliability. Engineered with Mercury Marine s advanced **MPI (Multi-Port Injection)** fuel delivery system, this 454 cubic-inch V8 delivers a robust **385 horsepower** at the propeller shaft, ensuring unmatched acceleration and towing capability while maintaining smooth, responsive performance across a wide RPM range. The **STB (Single Throttle Body)** configuration optimizes airflow and fuel mixture for improved throttle response and reduced emissions, making it ideal for boats requiring both power and precision, such as center console fishing vessels, offshore cruisers, or high-performance yachts.

One of the standout features of this engine is its **locked backward/forward (BW) gears**, which provide seamless shifting between forward and reverse without the need for a separate reverse gearbox. This design eliminates the complexity of traditional reverse systems, reducing maintenance requirements and improving overall reliability. The **MAG (Mercury Advanced Gearcase)** technology further enhances durability by incorporating a reinforced gearcase and optimized lubrication, ensuring longevity even under heavy loads or prolonged operation. Additionally, the engine s **Horizon series** designation signifies its integration with Mercury s advanced electronic controls, including the **Horizon Control Module**, which offers precise tuning for fuel efficiency, emissions compliance, and performance optimization.

Built to withstand the harshest marine environments, the 454 MPI MAG is constructed with high-strength materials, including a **cast iron block and aluminum cylinder heads**, which balance strength and weight for optimal power-to-weight ratio. The engine s **direct-drive configuration** (without a reduction gear) maximizes efficiency by transferring power directly to the propeller, while the **integrated exhaust system** ensures quiet operation and efficient heat dissipation. For added convenience and safety, the engine is equipped with **Mercury s MarineNet connectivity**, allowing for remote diagnostics, performance monitoring, and firmware updates via compatible apps, streamlining maintenance and troubleshooting for boat owners and dealers alike.

Whether powering a **high-speed center console** for offshore fishing, a **luxury cruiser** for long-range voyages, or a **commercial workboat** for heavy-duty applications, the **Mercruiser Horizon 454 MPI MAG/385HP STB Locked BW Gears** delivers a compelling combination of power, durability, and cutting-edge technology. Its **low-maintenance design**, **superior fuel economy**, and **rugged construction** make it a top-tier choice for discerning boaters who demand both performance and reliability in every outing. With Mercury Marine s reputation for innovation and quality, this engine stands as a testament to the brand s commitment to excellence in marine propulsion.

### **Pros and Cons of Buying a Mercruiser 0L006337/P 0L006338 Horizon 454 MPI (385 HP) with STB Locked BW Gears**

#### **Pros**

1. **Power and Performance**

The 454 MPI engine delivers **385 horsepower**, making it one of the most powerful Mercruiser inboard engines available in its class. This provides strong acceleration, high top-end speed, and excellent towing capacity, ideal for larger boats, cruisers, or performance applications.

2. **Reliability and Durability**

Mercruiser s **Horizon series** is known for its robust construction, high-quality materials, and proven reliability. The MPI (Multi-Port Injection) fuel system is well-regarded for efficiency and performance, reducing the risk of common fuel system issues found in older carbureted engines.

3. **STB (Sterndrive) Locked BW Gears**

- **Docking and maneuvering** in tight spaces.

- **Towing applications** where additional thrust is needed.

- **Boat handling in strong currents or wind** without relying solely on the stern drive.

This feature is particularly valuable for **fishing boats, cruisers, or workboats** where precise control is essential.

4. **Compatibility with Modern Boats**

- **Cruising yachts**

- **Performance cruisers**

- **Trawlers**

- **Fishing boats** (especially with additional gear options)

The engine s torque and power make it well-suited for **long-range cruising** and **high-speed cruising** applications.

5. **Fuel Efficiency (Compared to Similar Engines)**

While not the most fuel-efficient engine in its class, the **MPI system** improves efficiency over older carbureted Mercruisers. It also benefits from **direct injection** in some variants, which can help with power delivery and fuel economy.

6. **Aftermarket Support and Parts Availability**

- **Widespread availability of parts** (both OEM and aftermarket).

- **Numerous marine mechanics and dealerships** familiar with the engine.

- **Upgradability options** (e.g., exhaust systems, fuel injectors, performance chips).

7. **Resale Value**

Mercruiser engines, especially newer MPI models, hold their value well compared to some competitors. The **Horizon series** is highly regarded in the marine industry, which can make resale easier if you decide to upgrade later.

8. **Quiet Operation**

The **Horizon series** is known for being **quieter than older Mercruiser engines**, reducing cabin noise during cruising an important factor for liveaboard or long-range boats.

---

#### **Cons**

1. **High Initial Cost**

- **Engine price** ( $30,000 $40,000 new, depending on configuration).

- **Installation costs** (labor-intensive, requiring professional fitting).

- **Additional gear options** (e.g., BW thrusters, custom exhaust, cooling systems).

This makes it a **significant investment**, which may not be justified for smaller boats or casual users.

2. **Complexity and Maintenance Requirements**

- **More moving parts** (due to BW gears and MPI system) mean **higher maintenance costs** over time.

- **Sterndrive systems** (especially with BW thrusters) require **regular lubrication, alignment checks, and potential repairs**.

- **Fuel system maintenance** (MPI injectors can clog if not properly serviced).

- **Cooling system demands** (larger engines need **adequate raw water cooling** to prevent overheating).

3. **Weight and Space Considerations**

- The **454 MPI is heavy** ( 1,200 1,500 lbs depending on configuration), which may require **structural reinforcement** in the boat s transom.

- **BW thrusters take up additional space**, which may limit storage or other equipment options.

4. **Fuel Consumption**

While better than older carbureted engines, the **454 MPI still consumes fuel at a high rate** ( 1.5 2.5 gallons per hour at cruising speeds, depending on load).

- **Not ideal for ultra-long-range cruising** unless paired with a **large fuel tank**.

- **Expensive to operate** compared to smaller, more efficient engines.

5. **Noise and Vibration at High RPM**

- Despite being quieter than older models, the **454 MPI can still be loud at wide-open throttle (WOT)**.

- **Vibration levels** may be noticeable in smaller boats, requiring **proper mounting and isolation**.

6. **Limited Availability of Used Engines**

- The **Horizon series is relatively new**, so **used examples are rare** (unlike older Mercruiser 50s or 60s).

- If buying used, **inspection is critical** MPI engines can have **hidden fuel system or electrical issues**.

7. **Potential for Higher Repair Costs**

- **Mercruiser dealerships charge premium rates** for labor and parts.

- **Independent mechanics may not be as familiar** with the engine, leading to higher repair bills.

- **BW thrusters can be a weak point** if they fail, repairs can be **costly and time-consuming**.

8. **Not Ideal for Shallow Water or Small Boats**

- The **size and power** of the 454 MPI make it **overkill for small boats** (under 25 feet).

- **BW thrusters may not be necessary** for boats that don t need extreme maneuverability.

9. **Electrical System Demands**

- The **MPI system requires a robust electrical setup** (alternator, battery, wiring).

- **Starting and charging systems** must be **properly sized** to handle the engine s demands.

10. **Resale Depreciation Risk**

- While Mercruiser holds value well, **high-performance engines depreciate faster** than smaller, more fuel-efficient alternatives.

- If you plan to **upgrade later**, the **resale value may not offset the initial cost**.

---

### **Ending Conclusion**

The **Mercruiser 0L006337/P 0L006338 Horizon 454 MPI (385 HP) with STB Locked BW Gears** is a **powerful, reliable, and versatile engine** best suited for **larger, high-performance boats** where **maneuverability, towing capacity, and speed** are priorities. It excels in:

- **Cruising yachts** (30 feet)

- **Performance fishing boats**

- **Trawlers and workboats**

- **Boats requiring extreme docking control**

- **Small or budget boats** (under 25 feet)

- **Ultra-long-range cruising** (due to fuel consumption)

- **Casual weekend users** (high maintenance and cost)

- **Boats in shallow or restricted waters**

### **Recommendation**

You have a **large, powerful boat** (30 feet) that needs **high speed, towing, or precise maneuvering**.

You **prioritize reliability and performance** over fuel efficiency.

You are **prepared for higher maintenance and operational costs**.

You **plan to keep the boat long-term** (resale value is decent but not exceptional).

You **need BW thrusters** for docking, towing, or boat handling in challenging conditions.

You are on a **tight budget** consider a **smaller Mercruiser (e.g., 300 400 HP) or a Yamaha/Fujikin alternative**.

Your boat is **small or lightweight** a **less powerful engine (e.g., 250 350 HP) would be more efficient**.

You **frequently cruise long distances** look for **more fuel-efficient options (e.g., diesel engines like Yanmar or Cummins)**.

You **lack experience with high-performance marine engines** maintenance and repairs can be complex.

This engine is a **top-tier choice for serious boaters** who need **maximum power and control** but comes with **higher costs and maintenance demands**. If you can justify the investment and have the right boat, it is an **excellent long-term powerplant**. For most casual or budget-conscious buyers, a **smaller Mercruiser or a different brand** may be a more practical option.

Details:

I have the Mercury diagnostic tool but bottom half of screen in out, can not see engine hours. Boat was running and driving perfectly prior to lock up in the stb engine, happy share videos. Ill get the hours and update listing. Starboard Serial# 0L006337 Port Serial #0L006338 Estimated engine hours is 1000-1200.

Reduction was listed as 1:1.5, both All wiring harnesses and engine components. Whats Included-, 2 Mercury Verizon Mag MPI 454 one running, locked up. Engines are sold As/Is, you can come inspect prior to purchase. The engines are still in the boat and complete, harnesses, etc.

Up for sale is a matching pair of Mercruiser Verizon 454 MPI MAG 385hp with Borg Warner Gears.

part #: 0l006337 price

• $15900.00

specifications completegengin:

• for models: 454
• brand: Mercruiser
• mpn: 0l006337/p
• part type: Gear
• stroke: 4-stroke
• engine hp : 385
• country of origin: United States

payments completegengin:

• cash
• wallet: Google-pay
• credit card: Mastercard
• other

seller completegengin:

• rating: 100.0%
• city: San Antonio, Texas
• # reviews: 211

offer completegengin:

• best offers: True
• sold: 0
• quantity: 1
• options: Seller-arranged-local-pickup
• started: June 5, 2026
• availability: In Stock

shipping completegengin:

returns completegengin:

• policy: No Returns

general completegengin:

• Boat Parts > Inboard Engines Components > Complete Gas Engines
• condition: Used

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