What Is the Weight of a Mercury 115 HP 4-Stroke Outboard?

The Mercury 115 HP 4-stroke outboard motor is one of the lightest in its class, with a dry weight of approximately 359 pounds (163 kg) for the standard ELPT model with a 25-inch shaft. This makes it a top choice for small to midsize center console boats, bay boats, and skiffs where weight distribution and transom load are critical factors ✅. Whether you're comparing engines for fuel economy, ease of mounting, or overall vessel balance, understanding the exact mercury 115 4 stroke weight helps ensure optimal performance and safety on the water.

Why Outboard Motor Weight Matters

⚙️ The weight of an outboard motor significantly influences several aspects of your boating experience. A heavier engine can shift the center of gravity aft, causing the bow to rise and reducing stability at planing speeds. Conversely, a lighter motor like the Mercury 115 4-stroke improves acceleration, hole shot, and fuel efficiency ⚡.

For owners of smaller vessels—especially those under 20 feet—the difference of even 20–30 pounds on the transom can affect:

• Boat trim and balance: Excess stern weight may lead to porpoising or reduced maneuverability.
• Fuel consumption: Heavier motors require more power to move, increasing fuel use over time.
\li> Launch and retrieval effort: Especially important when using lifts or trailers 🚚.
• Engine longevity: Properly matched weight reduces strain on mounting hardware and lower units.

This is why Mercury designed the 115 HP FourStroke as the “lightest engine in its category” according to Alberni Power & Marine¹, emphasizing both performance and practicality for everyday boaters.

Mercury 115 4-Stroke Weight by Model and Shaft Length

Not all Mercury 115 HP 4-stroke models weigh the same. Variations come from shaft length, gearcase type, and additional features such as Command Thrust or Pro XS tuning. Below is a detailed breakdown:

Model	Shaft Length	Weight (lbs)	Weight (kg)	Key Features
Mercury 115ELPT	20" (Short)	353	160	Standard gearcase, mechanical controls
Mercury 115ELPT	25" (Long)	359	163	Most common configuration
Mercury 115XLPT	30" (Extra Long)	368	167	Suitable for larger transoms or cuddy cabins
Mercury 115CT	25"	375	170	Command Thrust gearcase for improved low-speed thrust
Mercury Pro XS 115	25"	345	156	Race-inspired design, higher displacement, lighter materials

As shown, the Pro XS 115 is the lightest variant at just 345 lbs (156 kg), making it ideal for performance-focused applications like bass boats or flats fishing rigs. On the other end, the Command Thrust (CT) version adds about 16 lbs due to its larger-diameter, low-rpm optimized propeller and reinforced lower unit, which enhances pushing power in shallow water or heavy loads ✨.

How Weight Affects Real-World Performance

📍 While dry weight is useful for comparison, real-world impact depends on how that weight is distributed and what kind of boat you have. Let’s explore three common scenarios:

1. Small Skiffs and Bay Boats (16–19 ft)

These lightweight fiberglass or aluminum boats benefit greatly from a lighter motor. The standard Mercury 115ELPT at 359 lbs allows quicker planing and better fuel economy compared to older or heavier four-strokes. According to Saltwater Experience’s YouTube review², users report “noticeably snappier acceleration” and improved range when switching from Japanese-brand equivalents.

2. Center Consoles with T-top or Electronics

Larger center consoles often carry significant forward weight (t-tops, fishfinders, live wells). Adding a heavier outboard could imbalance the vessel. In this case, opting for the Pro XS 115 (345 lbs) instead of the standard model helps maintain equilibrium without sacrificing horsepower.

3. Pontoon or Dual-Motor Setups

If running twin 115s on a pontoon, every pound counts. At 359 lbs each, two standard engines add 718 lbs to the transom. Switching to Pro XS models saves 28 lbs total—equivalent to removing a full cooler of gear. That reduction translates into faster starts and less draft.

Understanding Dry Weight vs. Wet Weight

📌 It's crucial to distinguish between dry weight and wet weight. The published mercury 115 4 stroke weight refers to dry weight—the engine alone without oil, fuel, or accessories.

• Dry weight: Engine only, no fluids
• Wet weight: Includes ~4 quarts of engine oil (~8 lbs) and gear lube (~2 lbs)

So, while the listed weight might be 359 lbs, the actual installed weight will be closer to 369 lbs. Always factor in these extra pounds when calculating total transom load, especially if your boat has a maximum engine weight limit specified by the manufacturer.

Comparison With Competitors

To put Mercury’s weight advantage in perspective, here’s how the 115 HP FourStroke stacks up against similar models from major brands:

Engine	Horsepower	Weight (lbs)	Weight (kg)	Notes
Mercury 115ELPT	115	359	163	Lightest standard 115-class engine
Yamaha F115	115	386	175	Heavier despite similar output
Toyota F115	115	382	173	Built under license from Yamaha
Suzuki DF115	115	373	169	Moderate weight, good reliability
Honda BF115	115	378	171	Smooth operation but heavier

⚡ As seen above, Mercury holds a clear edge in weight savings—up to 27 lbs lighter than the Yamaha F115. For performance-oriented buyers, this difference can mean faster hole shot, better fuel economy, and easier trailering.

Does Lighter Mean Less Durable?

🔧 A common concern among buyers is whether reduced weight compromises durability. However, Mercury achieves its low mass through advanced engineering rather than cost-cutting:

• Aluminum alloy construction: High-strength, corrosion-resistant materials reduce bulk without weakening components.
• Compact design: Integrated electronics and streamlined housing contribute to space and weight savings.
• SmartCraft compatibility: Digital gauges and diagnostic tools allow proactive maintenance, extending engine life regardless of weight.

There is no evidence to suggest that the lighter Mercury 115 HP 4-stroke sacrifices longevity. In fact, many owners report reliable service beyond 1,500 hours with proper maintenance—a point supported by Brinson Marine’s annual maintenance videos³.

Maintenance Tips to Preserve Performance

🧼 Keeping your Mercury 115 running efficiently starts with routine care. Even minor neglect can offset the benefits of a lightweight, high-efficiency engine. Follow these best practices:

1. Change Oil Annually or Every 100 Hours

Use Mercury Premium Full Synthetic 10W-30 or equivalent. Fresh oil ensures smooth internal operation and prevents wear that could increase operating weight through friction buildup.

2. Inspect and Replace Fuel Filters

Water-contaminated fuel degrades performance and increases carbon deposits. Replace primary and secondary filters per owner’s manual—typically every 100 hours or annually.

3. Service the Water Pump Every 300 Hours

A failing impeller leads to overheating, which stresses metal components and shortens engine life. FloBass’ service tutorial⁴ shows how to replace it safely.

4. Grease Steering and Tilt Mechanisms

Prevent binding and uneven stress on mounts. Use marine-grade grease on all zerk fittings twice per season.

5. Flush After Saltwater Use

Connect a flush mitten and run freshwater for 5–10 minutes after every saltwater trip to prevent corrosion inside cooling passages.

Pricing and Availability (2025–2026 Models)

🛒 As of early 2025, new Mercury 115 HP 4-stroke engines range from $11,500 to $14,600 USD depending on model and dealer location:

• Mercury 115ELPT (25"): ~$11,500–$12,400
• Command Thrust CT: ~$13,200–$13,800
• Pro XS 115: ~$14,000–$14,600

Dealers like Boat Country USA and Leaders RPM list current inventory with available rebates⁵. Prices vary regionally due to shipping, taxes, and demand, so always request a written quote before purchasing.

Common Misconceptions About the Mercury 115 4-Stroke

❌ Despite strong reviews, some myths persist. Let’s clarify:

• Myth: It’s underpowered for larger boats.
  Reality: With 112.6 brake horsepower at 5,500 rpm and peak torque at 3,500 rpm⁶, it performs well on boats up to 22 feet with moderate loads.
• Myth: Lightweight means noisy or rough operation.
  Reality: The four-cylinder DOHC design runs smoothly across the RPM band, often quieter than V6 two-strokes.
• Myth: Hard to find parts or service.
  Reality: Mercury has one of the largest global dealer networks. OEM parts are widely available through authorized distributors.

Final Considerations Before Buying

📌 Choosing the right Mercury 115 model comes down to matching engine specs to your boat and usage:

• Need raw speed and agility? Go with the Pro XS 115 (345 lbs).
• Towing kids or skiers frequently? The Command Thrust version offers better low-end punch.
• On a budget? The standard ELPT delivers excellent value and lowest initial cost.
• Saltwater use? Ensure anti-corrosion protection and commit to regular flushing.

Always verify compatibility with your boat’s transom height, recommended horsepower range, and maximum engine weight. Consult your vessel’s capacity plate and talk to a certified marine technician before installation.

Frequently Asked Questions

❓ How much does a Mercury 115 HP 4-stroke weigh?

The standard Mercury 115ELPT with a 25-inch shaft weighs 359 lbs (163 kg). The Pro XS model is lighter at 345 lbs, while the Command Thrust version weighs 375 lbs.

❓ What is the lightest 115 HP outboard motor?

The Mercury Pro XS 115 is currently the lightest 115 HP four-stroke outboard, weighing just 345 lbs (156 kg), giving it an edge in performance and efficiency.

❓ Does the Mercury 115 4-stroke require premium fuel?

No, it runs on 87-octane regular unleaded gasoline. However, using ethanol-free fuel or adding a stabilizer can improve long-term reliability, especially in marine environments.

❓ How long do Mercury 115 4-stroke engines last?

With proper maintenance, most last 1,500 to 2,000 hours. Many reach 10+ years of dependable service in recreational use.

❓ Can I mount a Mercury 115 on a small boat?

Yes, but check your boat’s capacity plate for maximum horsepower and transom weight limits. Most 17–20 foot boats handle the 359-lb motor well, especially with proper trim adjustment.