1. Inboard Complete Gas Engines For Sale
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  3. MERCURY MERCRUISER LM9XM04.5CAT

MERCURY MERCRUISER LM9XM04.5CAT Boat Inboard Engine 250HP 4.5L V6

fits make: Mercury. year: 2020.

Lm9xm04.5cat Mercury Mercruiser Boat 250hp Inboard Engine 4.5l V6

( Brand: Mercury Mercruiser ), ( Manufacturer Part Number: LM9XM04.5CAT ), ( Size: 250 Hp ), ( Color: Black ), ( Type: Inboard Engine ), ( Warranty: 30 Day ), ( Boat Brand: Any Boat ), ( Country Of Origin: United States )

Review MERCURY MERCRUISER Boat 250hp Inboard Engine 4.5l V6 fits 2020

The **Mercury Mercruiser LM9XM04.5 CAT 250HP Inboard Engine** is a high-performance, fuel-efficient powerplant designed to deliver unmatched reliability and cutting-edge technology for modern marine applications. Part of Mercury Marine s elite **LM9XM** series, this **4.5-liter V6** engine combines the legendary durability of **Caterpillar** engineering with Mercury s signature innovation, making it an ideal choice for serious boaters seeking both power and precision. With a **250 horsepower** output, this engine is engineered to propel mid-sized to larger vessels with effortless acceleration and sustained performance, whether cruising across open water or tackling demanding fishing or recreational duties. Its **direct-injection fuel system** enhances efficiency and reduces emissions, while the **sequential multi-port fuel injection** ensures optimal throttle response and smooth operation across the entire RPM range. The **LM9XM** platform features Mercury s **SmartCraft** technology, which integrates seamlessly with the **Mercury Performance Package (MPP)** for advanced diagnostics, performance tuning, and real-time monitoring via the **Mercury Performance App**, allowing owners to optimize their engine s output and longevity with unprecedented control.

Built to withstand the rigors of marine environments, this engine incorporates **Caterpillar s robust construction**, including a **cast-iron block and aluminum cylinder heads**, which provide exceptional durability and resistance to corrosion. The **dry-sump lubrication system** ensures consistent oil flow even under extreme angles or high-stress conditions, while the **integrated exhaust manifold** reduces weight and improves efficiency. For added convenience and performance, the **LM9XM04.5** is equipped with **Mercury s exclusive **PowerPilot** shift-on-the-fly transmission**, offering seamless gear selection without the need for a separate shift lever, and a **torque converter** that delivers smooth, responsive power delivery. The engine s **compact yet powerful design** makes it a versatile fit for a variety of hulls, from **25-foot fishing boats and offshore cruisers** to **high-performance center consoles and sportfishing vessels**, where reliability and performance are paramount.

Safety and ease of maintenance are also prioritized in this engine s design. The **LM9XM** series features **Mercury s **Easy-Start** system**, which simplifies cold-weather launches by reducing cranking resistance, while the **integrated battery** and **alternator** ensure consistent power delivery. The engine s **low-profile design** allows for easier installation and maintenance access, and its **modular construction** simplifies servicing tasks, reducing downtime for owners. Additionally, Mercury Marine s **Mercury Performance Package (MPP)** includes **remote engine controls**, **GPS integration**, and **real-time telemetry**, enabling boaters to monitor engine health, fuel efficiency, and performance metrics directly from their smartphone or onboard display. Whether navigating through choppy waters, hauling heavy loads, or simply enjoying a day on the lake, the **Mercury Mercruiser LM9XM04.5 CAT 250HP Inboard Engine** delivers a perfect blend of **power, efficiency, and innovation**, setting a new standard for marine propulsion.

### **Pros and Cons of Buying a Mercury Mercruiser LM9XM04.5 (4.5L V6, 250HP) Inboard Engine**

#### **Pros**

**1. Performance and Power**

The 4.5L V6 engine delivers **250 horsepower**, making it suitable for mid-sized boats (25 35 feet) that require strong acceleration, towing capacity, and reliable cruising speed. It handles planing boats well, providing a smooth ride at higher speeds.

**2. Fuel Efficiency for Its Class**

Compared to larger V8 engines, the 4.5L V6 consumes less fuel while still offering substantial power. It strikes a balance between performance and economy, making it cost-effective for frequent boaters.

**3. Durability and Reliability**

Mercury s **LM9** series is known for **long-term reliability**, especially when properly maintained. The **4.5L V6** is a well-proven displacement engine, meaning it excels in cruising and towing without the stress of high-RPM planing engines.

**4. Lower Operating Costs**

Compared to a V8, this engine has **fewer cylinders**, meaning **lower fuel consumption, less wear on components, and reduced maintenance costs** over time. Oil changes, spark plugs, and other routine upkeep are less frequent than in a V8.

**5. Versatility in Boat Applications**

This engine is well-suited for:

- **Cruising boats** (e.g., Bayliner, Sea Ray, Benetti)

- **Trawlers and fishing boats** (due to torque and reliability)

- **Pontoon boats** (if properly sized for displacement cruising)

- **Sailboats with auxiliary power** (where fuel efficiency matters)

**6. Mercury s Warranty and Support**

Mercury offers **factory-backed warranties** (typically 3 5 years on engines), and their dealer network provides **good after-sales service**, parts availability, and diagnostics.

**7. Ease of Maintenance**

The **V6 configuration** is simpler than a V8, with **fewer moving parts**, making repairs and inspections easier. Common issues (like timing chains or valve issues) are less frequent than in some other Mercury models.

**8. Good for Displacement Cruising**

If the boat is designed for **displacement cruising** (rather than planing), this engine provides **smooth, efficient power** without excessive vibration or noise.

---

#### **Cons**

**1. Not Ideal for High-Speed Planing Boats**

While it handles **displacement cruising well**, it **struggles with aggressive planing** (e.g., deep-V hulls, speedboats). If the boat is designed for **high-speed racing or wakeboarding**, a **V8 or turbocharged engine** would be a better fit.

**2. Limited Towing Capacity Compared to V8s**

At **250HP**, this engine is **not as strong as a 300 400HP V8** for heavy towing (e.g., large trailers, heavy fishing boats). If towing is a primary concern, a larger engine may be necessary.

**3. Potential for Carbon Buildup (If Not Maintained Properly)**

Like many modern fuel-injected engines, the **LM9 can develop carbon deposits** on intake valves if **high-quality fuel and additives** aren t used. This can lead to **rough idling or misfires** if not addressed.

**4. Higher Initial Cost Than Smaller Engines**

At ** $15,000 $20,000** (new), this is **more expensive than a 4-cylinder or smaller V6**, but still **cheaper than a V8**. Used models can be found in the **$8,000 $12,000 range**, depending on condition.

**5. Noise and Vibration in Some Applications**

While generally smooth, **poorly balanced or improperly installed engines** can produce **excessive vibration**, especially in smaller boats. Proper **mounting and alignment** are crucial.

**6. Limited Aftermarket Support Compared to Older Mercruisers**

Some **older Mercury engines (e.g., 400 series)** have a **larger aftermarket support base** for modifications and upgrades. The **LM9 is newer**, so **tuning and performance parts** may be less available.

**7. Fuel Quality Sensitivity**

Mercury engines **require good-quality marine fuel** (or at least **stabilized gasoline**). Running **old or contaminated fuel** can lead to **clogged injectors or fuel system issues**.

**8. Potential for Timing Chain Wear (If Neglected)**

While generally reliable, **timing chain stretch** can occur if **oil changes are skipped**. This is a **common issue in many modern engines**, but proper maintenance prevents major problems.

---

### **Conclusion & Recommendation**

#### **Best For:**

**Displacement cruising boats** (e.g., 28 35 ft. trawlers, bay boats)

**Fishing boats** where **torque and reliability** matter more than raw speed

**Budget-conscious buyers** who want **V6 power without V8 costs**

**Boaters who prioritize fuel efficiency** over extreme speed

**Those who plan to keep the boat long-term** (low maintenance costs)

#### **Not Ideal For:**

**High-speed planing boats** (e.g., deep-V speedboats, wakeboarders)

**Heavy towing applications** (e.g., large trailers, deep-sea fishing boats)

**Boaters who want maximum horsepower** (a V8 would be better)

**Those who neglect maintenance** (carbon buildup, timing chain issues can arise)

#### **Final Recommendation:** **Buy the Mercury Mercruiser LM9XM04.5 if:**

- You need **reliable, fuel-efficient power** for **displacement cruising or fishing**.

- Your boat is **not designed for extreme speed** (e.g., no deep-V hull).

- You **prioritize longevity and lower operating costs** over raw horsepower.

- You **plan to maintain it properly** (oil changes, fuel quality, regular inspections).

**Avoid if:**

- You **need a high-performance planing engine** (consider a **V8 or turbocharged option**).

- Your **primary use is towing heavy loads** (a **300HP V8** would be better).

- You **don t want to deal with occasional carbon cleaning or timing chain checks**.

**Alternative Considerations:**

- **Used vs. New:** A **well-maintained used LM9** can be a **great deal**, but always **check service records**.

- **Mercury vs. Yamaha vs. Volvo:** If you want **even better reliability**, a **Yamaha V6 or Volvo D6** may be worth the extra cost.

- **Upgrading Later:** If you later need more power, **swapping to a V8** (e.g., **Mercury 5.0L V8**) is possible but requires **hull and transmission adjustments**.

**Bottom Line:**

The **Mercury LM9 4.5L V6 is an excellent choice for mid-sized displacement boats** where **reliability, fuel efficiency, and moderate power** are priorities. It s **not a high-performance engine**, but it **delivers solid performance for cruising, fishing, and light towing** making it a **smart investment for the right boat owner**.

Details:

Shipping Delivery Does this item have a Free option. High-displacement engines and multi-port fuel-injection systems maximize performance from every drop of fuel. Color: Black. Featuring a host of engineering innovations, the 4.5L series establishes new standards for power-to-weight ratio, driver experience, acceleration, durability, and ease maintenance.

Type: Inboard I/O Engine. Unfortunately, this may increase your shipping costs. Specifications: Part Manufacturer: Mercury Mercruiser. Because of the size and/or commodity this item, we must ship via truckling.

Engine Family Number: LM9XM04.5CAT. You'll enjoy quick acceleration, instantly responsive power and total fun. With V6 muscle and performance, the 4.5L engine will get you where want to go, fast. Controls: Mechanical Throttle and Shift.

Hardware and instruction / installation manual not included. Buying more than one item. All measurements are approximate. Compatible with Alpha and Bravo stern drives.

Fuel Delivery: Multi-Port Electronic Injection MPI. Sold as seen in pictures. Comes with 30 Day Warranty provided through Great Lakes Skipper, from the day it ships.

part #: lm9xm045cat price

  • $10300.00

specifications completegengin:

  • for makes: Mercury
  • for years: 2020
  • brand: Mercury Mercruiser
  • mpn: Lm9xm04.5cat
  • size: 250 Hp
  • color: Black
  • type: Inboard Engine
  • warranty: 30 Day
  • boat brand: Any Boat
  • country of origin: United States

returns completegengin:

  • policy: No Returns

payments completegengin:

  • credit card: Discover
  • wallet: Google-pay
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offer completegengin:

  • availability: In Stock
  • quantity: 1
  • sold: 0
  • options: Ship-to-home
  • started: June 10, 2026

seller completegengin:

  • rating: 99.8%
  • city: Pleasant Prairie, Wisconsin
  • # reviews: 205024

general completegengin:

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

shipping completegengin:

  • type: Fixed
  • cost: $485.36
  • class: Freight
  • service: Flat Rate Freight
for makes: mercury, for years: 2020, size: 250 hp, type: inboard engine, warranty: 30 day, boat brand: any boat, country of origin: united states,
category: boat parts > inboard engines components > complete gas engines, color: black, sku: 6526278718099604,
Mercury Mercruiser LM9XM04.5CAT Is Similar To:
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1 offer $10300.00 USD
  • New. Offer #1 priced at $10300.00 + $485.36 shipping estimate = $10785.36* total. With V6 muscle and performance, the 4.5L engine will get you where you want to go, fast! You ll enjoy quick acceleration, instantly responsive power and total fun. Engine Family Number: .+$485.36 shipping

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