What to Know About 40hp Yamaha 2-Stroke Outboard Motors

If you're searching for a reliable, lightweight power source for your skiff, jon boat, or small fishing craft, the 40hp Yamaha 2-stroke outboard may be on your radar—especially if you value simplicity, strong acceleration, and proven durability in saltwater environments. While Yamaha has largely shifted to four-stroke technology, many boaters still seek used or vintage 40hp two-stroke models for their responsive performance and ease of maintenance. This guide breaks down everything you need to know about these engines: specifications, model years, common problems, weight, fuel efficiency, and how they compare with modern alternatives.

Understanding the 40hp Yamaha 2-Stroke Outboard Legacy

The 40 horsepower Yamaha 2-stroke outboard was once a staple in Yamaha’s midrange lineup, particularly popular from the 1980s through the early 2000s. These engines were known for their compact size, high power-to-weight ratio, and straightforward mechanical design. Unlike today’s electronically managed four-strokes, the older 2-stroke models relied on carburetors, manual choke systems, and simpler ignition setups—making them easier to repair in remote locations or onboard small vessels without advanced tools.

Yamaha produced several variations of the 40hp 2-stroke over the decades, including models with tiller handles and remote steering options. Shaft lengths typically came in 20-inch (standard) and 25-inch (long) versions to accommodate different transom heights. The engine block was usually a two-cylinder or three-cylinder configuration, depending on the production year and market region.

Key Specifications of the 40hp Yamaha 2-Stroke

While exact specs can vary slightly between model years, most 40hp Yamaha 2-stroke outboards share core characteristics that define their performance and usability:

Feature	Typical Specification
Engine Type	Two-stroke, inline 2 or 3 cylinder
Horsepower	40 hp @ 5,000–5,800 RPM
Displacement	740–760 cc
Weight (dry)	125–145 lbs (57–66 kg)
Shaft Length	20" (standard), 25" (long)
Fuel System	Carbureted, pre-mix or oil injection
Starting Method	Recoil (rope) pull start
Alternator Output	6A–12A (varies by model)

⚙️ One of the standout features of these engines is their relatively low dry weight—often under 140 pounds—which makes them ideal for lightweight boats like aluminum jon boats, inflatable pontoons, and small fiberglass skiffs. This lightness contributes to better weight distribution and improved planing ability compared to heavier four-stroke equivalents.

Model Variants and Identification Tips

Yamaha did not use consistent naming conventions across all markets or eras, so identifying a specific 40hp 2-stroke model requires checking the serial number and engine tag. Common designations include:

• Yamaha F40TLRU: Tiller-start, long shaft, remote control option
• Yamaha V40EL: Electric start, long shaft, oil-injection system
• Yamaha 40U: Early 1980s model with dual carbs

🔍 To identify your model, locate the metal data plate near the mounting bracket. It will list the model code, serial number, and year of manufacture. You can cross-reference this with Yamaha’s official archives or third-party databases like the Yamaha Outboards website1 to confirm compatibility and parts availability.

Performance and Real-World Use Cases

The 40hp Yamaha 2-stroke delivers brisk acceleration and solid top-end speed for boats weighing up to 2,500 pounds fully loaded. On a typical 16-foot aluminum fishing boat, users report speeds between 28–35 mph, depending on load, hull condition, and propeller pitch.

⚡ Because 2-stroke engines produce power on every revolution, they tend to feel more responsive than four-strokes of similar horsepower, especially when coming onto plane. However, they also consume more fuel—typically 4–6 gallons per hour at cruising speed—and require mixing oil with gasoline unless equipped with an autolube system.

📍 Common applications include:

• Fishing in shallow inland lakes and rivers
• Backcountry exploration where portability matters
• Duck hunting blinds and marsh access
• Small pontoon or utility rafts

Users often praise the engine’s ability to run reliably in saltwater with proper flushing, though corrosion protection remains critical due to exposed aluminum components.

Advantages of the 40hp Yamaha 2-Stroke

Despite being phased out in favor of cleaner four-strokes, the 40hp 2-stroke retains loyal followers. Here are its main benefits:

✅ Simplicity: Fewer moving parts mean less that can go wrong mechanically. No complex emissions systems or computer modules.✅ Lightweight: Weighs significantly less than modern 40hp four-strokes (which often exceed 200 lbs), improving boat balance and trailer capacity.✅ Power Delivery: Smooth, linear throttle response with strong mid-range torque—ideal for quick starts and maneuvering in tight spots.✅ Ease of Repair: Most mechanics and even experienced DIYers can rebuild or troubleshoot these engines using basic hand tools.✅ Availability of Parts: Even though no longer in production, OEM and aftermarket parts remain widely available through marine suppliers and online retailers like Alibaba.com ¹.

Disadvantages and Common Issues

No engine is perfect, and the 40hp Yamaha 2-stroke comes with trade-offs worth considering before purchase:

❗ Fuel Efficiency: These engines burn more fuel than modern four-strokes. At full throttle, expect 5–7 mpg, which limits range on smaller tanks.❗ Noise and Vibration: Two-strokes run at higher RPMs and produce a characteristic high-pitched whine, which some find fatiguing on long trips.❗ Emissions and Regulations: Many U.S. states and Canadian provinces restrict or ban carbureted 2-stroke engines on certain waterways due to pollution concerns. Always check local rules before operating. 2❗ Oil Injection Failures: Models with auto-lube systems can suffer from clogged lines or failed pumps, leading to seized engines if undetected. Regular inspection is essential.❗ Carburetor Deterioration: Ethanol-blended fuels can degrade rubber seals and varnish carb internals over time. Using fuel stabilizer and ethanol treatment is strongly advised.

How to Evaluate a Used 40hp Yamaha 2-Stroke

Since new units are no longer made, most buyers are looking at used engines. A thorough inspection can prevent costly surprises:

📋 Compression Test: Perform a compression check (should read 90–110 psi per cylinder). Low readings indicate worn rings or damaged pistons.📋 Spark Plug Inspection: Remove plugs and examine color. Tan to gray indicates good combustion; black or oily deposits suggest rich mixtures or burning oil.📋 Lower Unit Oil Check: Drain the gearcase oil. Milky fluid means water intrusion and potential seal failure.📋 Steering and Tilt Mechanism: Ensure smooth movement without grinding or stiffness, which could signal internal corrosion.📋 Serial Number Verification: Confirm the engine hasn’t been reported stolen via services like NICB or state registries.📋 History of Use: Saltwater exposure increases wear. Ask about winterization practices and whether the engine was flushed regularly.

Modern Alternatives: Four-Stroke vs. Two-Stroke

Today, Yamaha’s current 40hp offering—the F40LA—is a three-cylinder four-stroke with electronic fuel injection, delivering smoother operation, quieter running, and better fuel economy. But it weighs around 214 lbs, nearly 70 lbs more than its 2-stroke predecessor.

Here’s a direct comparison:

Criteria	40hp 2-Stroke (Vintage)	40hp 4-Stroke (F40LA)
Weight	~135 lbs	~214 lbs
Fuel Economy	4–6 GPH	2.5–3.5 GPH
Starting Method	Pull cord	Electric or tiller
Maintenance Complexity	Low	Moderate
Emissions Compliance	Limited areas	Fully compliant
Price (Used/New)	$1,500–$3,000	$6,500–$7,500

While the four-stroke wins in efficiency and noise reduction, the 2-stroke still appeals to those prioritizing weight savings and mechanical simplicity.

Where to Buy a 40hp Yamaha 2-Stroke

🛒 Since these engines are discontinued, your best options are:

• eBay: Wide selection, but verify seller reputation and request video demonstrations.
• Local Classifieds (Facebook Marketplace, Craigslist): Allows in-person inspection and testing.
• Marine Salvage Yards: Some specialize in refurbishing old outboards.
• Alibaba.com: For sourcing replacement parts or rebuilt units from international suppliers.3

When purchasing online, insist on clear photos of the engine tag, recent compression test results, and proof of servicing history. Avoid "untested" listings unless priced very low and intended for parts.

Maintenance Tips for Longevity

To keep a vintage 40hp Yamaha 2-stroke running well, follow these maintenance practices:

🔧 After Every Use: Flush the engine with fresh water, especially after saltwater runs.🔧 Every 50 Hours: Replace spark plugs, inspect carburetor jets, and check propeller for damage.🔧 Annually: Change lower unit oil, clean fuel tank and lines, and inspect rubber hoses for cracking.🔧 Before Storage: Fog the cylinders, stabilize the fuel, and remove the battery if equipped.🧼 Using non-ethanol fuel or adding an ethanol treatment (like Star-Tron or Sea Foam) helps prevent gum buildup in the carburetor—a common issue in stored engines.

Common Misconceptions About 2-Stroke Outboards

Several myths persist about older 2-stroke engines. Let’s clarify:

📌 Myth: All 2-strokes are polluting and outdated.
Reality: While less efficient than four-strokes, properly tuned 2-strokes with functioning oil injection meet acceptable emission standards in many regions.

📌 Myth: They’re unreliable compared to modern motors.
Reality: With regular care, these engines can last decades. Many still operate reliably after 2,000+ hours.

📌 Myth: You can’t get parts anymore.
Reality: Major components like carb kits, gaskets, impellers, and starters are still manufactured and sold globally.

Is a 40hp Yamaha 2-Stroke Right for You?

The answer depends on your priorities:

✨ Choose a 40hp Yamaha 2-stroke if:

• You need a lightweight motor for a small, lightweight boat.
• You prefer simple mechanics over digital complexity.
• You operate in areas where 2-strokes are still permitted.
• You’re on a budget and want to avoid the $7,000+ cost of a new four-stroke.

❌ Consider a modern four-stroke instead if:

• You prioritize fuel economy and quiet operation.
• You frequently travel long distances on open water.
• You live in a region with strict emissions regulations.
• You want electric start, remote throttle, and integrated gauges.

Frequently Asked Questions (FAQ)

❓ What years did Yamaha make the 40hp 2-stroke outboard?

Yamaha produced 40hp 2-stroke models from the late 1970s through the early 2000s, with peak availability in the 1980s and 1990s.

❓ How much does a 40hp Yamaha 2-stroke weigh?

Most models weigh between 125 and 145 pounds dry, making them significantly lighter than modern four-strokes.

❓ Can I still use a 40hp Yamaha 2-stroke legally?

In most U.S. states, yes—but some lakes and parks restrict older 2-strokes due to emissions. Always check local regulations before use.

❓ Are parts still available for 40hp Yamaha 2-stroke engines?

Yes, many OEM and aftermarket parts are still available through marine suppliers and online platforms like Alibaba.com.

❓ What kind of boat is best suited for a 40hp 2-stroke?

Ideal for boats between 14–18 feet, such as jon boats, skiffs, inflatables, and small pontoons with total weights under 2,500 lbs.