MERCURY 700-859563T17 Dfi Optimax Starboard Piston 135-175

( Manufacturer Part Number: 700-859563T17 ), ( Part Type: Hp Piston ), ( Country Of Origin: United States )

Review MERCURY Dfi Optimax Hp Starboard Side Piston fits MARINE

The **Mercury 700-859563T17 Marine DFi Optimax 135 175 HP Starboard Piston Engine** is a high-performance, fuel-efficient outboard motor designed to deliver unmatched power and reliability for serious anglers, boaters, and performance enthusiasts. Engineered with Mercury s legendary craftsmanship, this **DFi Optimax** model combines cutting-edge **Direct Fuel Injection (DFi)** technology with a **Starboard piston configuration**, ensuring optimal combustion efficiency, reduced emissions, and superior torque delivery across its **135 175 horsepower range**. The **Optimax cylinder head** features advanced porting and valve timing, enhancing airflow and maximizing power output while maintaining smooth operation, even under heavy loads. This engine is built to thrive in demanding conditions, whether you're trolling at low speeds for hours or pushing through rough waters at full throttle, thanks to its **robust aluminum construction** and **precision-machined components**.

One of the standout features of this engine is its **adaptive throttle response**, which adjusts fuel delivery in real-time for optimal performance, whether you're cruising, fishing, or racing. The **DFi system** eliminates carbon buildup on intake valves, reducing maintenance needs and extending engine life, while the **Optimax cylinder head** improves cooling efficiency, preventing overheating even in high-load scenarios. The **Starboard piston design** further enhances reliability by distributing stress more evenly across the piston rings, reducing wear and improving durability over time. With a **compact yet powerful footprint**, this engine is ideal for a wide range of vessels, from mid-sized fishing boats and performance cruisers to high-speed runabouts, offering a seamless blend of **performance, efficiency, and low maintenance**.

For those who demand precision and adaptability, the **700-859563T17** integrates seamlessly with Mercury s **EFI (Electronic Fuel Injection) system**, allowing for fine-tuned control via the **Mercury Performance Edge (MPE) app** or **Mercury Link** connectivity, where available. This smart technology enables remote monitoring of engine diagnostics, fuel efficiency, and performance metrics, ensuring you can optimize your outboard s operation with ease. The engine s **low-vibration design** and **balanced crankshaft** contribute to a quieter, smoother ride, making it a favorite among boaters who prioritize comfort without sacrificing power. Whether you're navigating calm waters or tackling choppy seas, this **135 175 HP DFi Optimax** delivers the **speed, torque, and endurance** needed to dominate the water.

Built to last, the **Mercury 700-859563T17** incorporates **high-performance materials**, including **forged crankshafts, precision-ground rods, and reinforced cylinder walls**, ensuring longevity even under the most demanding conditions. The **Optimax cylinder head** also features **enhanced cooling fins** and **optimized combustion chambers** for better heat dissipation and efficiency. With a **5-year limited warranty** on the engine block and **3-year limited warranty** on the powerhead (terms may vary by region), Mercury stands behind this outboard s quality, providing peace of mind for owners. Whether you're upgrading an existing vessel or specifying this engine for a new build, the **DFi Optimax 135 175 HP Starboard Piston** is a **game-changing powerplant** that sets a new standard for performance, reliability, and smart boating technology.

### **Pros and Cons of buying a Mercury 700-859563-T17 Marine DFi Optimax 135-175 HP (Starboard Piston Engine)**

The Optimax series is known for delivering strong torque and reliable power output, making it suitable for mid-sized boats (18-25 feet) that require smooth acceleration and good top-end speed. The 135-175 HP range provides flexibility for different boat types, from cruisers to performance boats.

Compared to older piston engines, the Optimax series offers improved fuel efficiency, reducing operating costs over time. The DFi (Direct Fuel Injection) system enhances combustion efficiency, leading to better mileage.

Mercury s piston engines have a long history of durability, especially in marine applications. The Optimax is built with robust materials and is designed for saltwater resistance, reducing corrosion risks. Proper maintenance can extend its lifespan significantly.

As a piston engine, it has fewer moving parts than modern outboards, which can translate to lower maintenance costs over time. However, this depends on usage and upkeep.

Mercury piston engines, particularly well-maintained Optimax models, hold their value reasonably well in the used market, especially if paired with a compatible boat.

If you re running a boat that wasn t originally designed for modern outboards, a piston engine like this can be a practical alternative, offering similar power without the need for extensive modifications.

Some boat owners prefer the straightforward mechanics of piston engines, which can be easier to diagnose and repair than complex outboard systems. However, this is subjective and depends on the owner s mechanical skill level.

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The upfront purchase price of a used Mercury Optimax in this power range can be higher than comparable modern outboards, especially if the engine is in excellent condition. Newer outboards often offer similar power at a lower cost.

While more efficient than older piston engines, the Optimax still consumes more fuel and oil than modern fuel-injected outboards. Oil changes are more frequent, and fuel economy is generally worse than that of modern two-stroke or four-stroke outboards.

Piston engines are significantly heavier than modern outboards, which can affect handling, fuel efficiency, and the structural integrity of the boat. This may require additional reinforcement or modifications.

Piston engines tend to be noisier and vibrate more than modern outboards, which can be less comfortable for passengers and may require soundproofing or vibration dampening.

Older piston engines, including the Optimax, produce more emissions than modern outboards with catalytic converters and advanced fuel systems. If you operate in environmentally sensitive areas, this could be a drawback.

Unlike newer outboards with electronic fuel injection, throttle-by-wire, and advanced diagnostics, the Optimax relies on older mechanical systems. This can make troubleshooting and repairs less intuitive for newer boat owners.

While Mercury still supports piston engines, parts and service can be harder to find compared to modern outboards. Some specialty shops may be required for repairs, increasing downtime and costs.

While piston engines hold value, they depreciate faster than newer outboards in the long term. If you plan to upgrade soon, the resale value may not justify the initial investment.

Even with proper maintenance, piston engines are more susceptible to saltwater corrosion than modern outboards with sealed systems. Regular flushing and desalination are essential.

The Optimax is optimized for steady cruising rather than high-performance racing. If you need extreme speed or agility, a modern outboard or sterndrive would be a better choice.

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### **Conclusion and Recommendation**

The **Mercury 700-859563-T17 Marine DFi Optimax (135-175 HP)** is a solid choice for boat owners who prioritize **reliability, durability, and lower maintenance costs** over the latest in fuel efficiency and technology. It excels in **mid-sized cruising boats, fishing vessels, or older models that weren t designed for modern outboards**. If you re looking for a **proven, long-lasting engine** that can handle heavy loads and rough conditions with proper care, this engine is a strong contender.

However, if you re seeking **better fuel economy, lower emissions, quieter operation, or the latest in marine technology**, a **modern outboard or sterndrive** (such as Mercury s Verado, Mercruiser Alpha, or Yamaha s F200 series) would be a more modern and efficient alternative. The Optimax is best suited for **budget-conscious buyers, traditionalists, or those who need a heavy-duty engine for demanding applications**.

- **Buy it if:** You need a **reliable, high-torque engine** for a **cruising or workboat**, have a **budget for maintenance**, and don t mind the **higher fuel/oil consumption and weight**.

- **Avoid it if:** You want **modern fuel efficiency, lower emissions, or the latest in marine technology**, or if you re operating in **highly regulated environmental zones**.

- **Consider alternatives:** If possible, explore **used modern outboards** (e.g., Mercury Verado, Yamaha F200) or **sterndrives** (Mercruiser Alpha) for better long-term performance and lower operating costs.

Would you like recommendations on maintenance tips or specific boat models this engine pairs well with?

Details:

Mercury Part # 700-859563T17, 700-859563T4. THIS IS A STARBOARD SIDE PISTON TAKEN OFF 2004 MERCURY 135 HP DFI OPTIMAX.

part #: 700859563t17 prices

• $49.99-$199.95

specifications ouboaen:

• for models: Marine
• for makes: Mercury
• mpn: 700-859563t17
• part type: Hp Piston
• country of origin: United States

general ouboaen:

• condition: Used
• Boat Parts > Outboard Engines Components > Other

returns ouboaen:

• policy: No Returns

offer ouboaen:

• sold: 0
• availability: In Stock
• quantity: 3
• best offers: True
• started: May 8, 2026
• options: Ship-to-home

shipping ouboaen:

• class: Expedited
• cost: $18.05
• carrier: USPS
• service: USPS Priority Mail
• type: Calculated
• transit: 5-11 Days

seller ouboaen:

• city: Kaukauna, Wisconsin
• rating: 100.0%
• # reviews: 8274

payments ouboaen:

• other
• wallet: Apple-pay
• credit card: Mastercard

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