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Yanmar 6LY3-STP – Inboard Diesel Engine 440 HP
Yanmar 6LY3-STP – 440 HP utilizes a flagship 5.8L inline-six propulsion architecture featuring a 24-valve cylinder head and full electronic control (Yanmar i5601E). This 440 HP unit is engineered for high-performance planing hulls, utilizing a specialized wastegated turbocharger to deliver rapid acceleration and smoke-free operation, making it the premier choice for luxury sportfishers and express cruisers requiring a compact diesel footprint with elite power density.
- Precision Operational Data: Rated at 440 HP (324 kW) at 3300 RPM.
- Internal Engine Configuration Type: Inline 6-Cylinder 24-Valve 5.81L Displacement.
- Advanced Fuel Delivery System: Electronic Control with Precision Direct Injection.
- Recommended Vessel Application Use: Ideal for performance sportfishers and luxury motor yachts.
- Factory Protection Service Plan: Yanmar limited manufacturer warranty coverage.
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Description
Yanmar 6LY3-STP 440 HP – High-Output Yacht Propulsion Engine
Overcoming the weight-to-power limitations of mid-sized cruisers, the Yanmar 6LY3-STP delivers a potent 440 HP at 3300 RPM. This engine is specifically engineered for the American recreational yacht market, offering a high-performance in-line 6-cylinder configuration that minimizes vibration and enhances passenger comfort. The sophisticated turbocharging system provides the high-end speed required for long-distance cruising across the Florida Strait or the Pacific Northwest Sounds with exceptional reliability.
Ensuring full compliance with USA EPA Tier 3 mandates, the 6LY3-STP utilizes advanced common-rail technology to eliminate the soot and odor typically found in older diesel generations. This clean-burning performance is paired with Yanmar’s E-Controls, providing American yacht owners with digital throttle precision and integrated vessel management capabilities. The oversized heat exchanger and high-efficiency cooling system are built to handle high-ambient temperatures in tropical US waters, maintaining peak performance under load.
Core Technical Specifications
- Maximum Output: 440 HP at 3300 RPM.
- Displacement: 354 cubic inches (5.813 Liters).
- Configuration: 6-cylinder, 4-stroke, vertical diesel.
- Aspiration: Turbocharged with charge air cooler.
- Dry Weight: Approximately 1411 lbs with KMH61A gear.
- Electrical: 12V / 80A marine alternator.
- Compliance: EPA Tier 3 and RCD2 certified.
- Fuel Injection: High-pressure common rail.
Yanmar 6LY3-STP Full Specs
| Engine type | In-line 6, 4-stroke Diesel |
| Displacement | 5.813L (354 cid) |
| Bore x stroke | 106 x 110 mm |
| Horsepower | 440 hp (324 kW) |
| Rated rpm | 3300 rpm |
| Aspiration | Turbocharged & Intercooled |
| Compression ratio | 16.7:1 |
| Fuel system | Electronic Common Rail |
| Recommended fuel | Diesel (EN 590) |
| Ignition/Firing Order | Compression / 1-5-3-6-2-4 |
| Alternator | 12V, 80 Amp |
| Gear ratio/Drive | KMH61A / ZF compatible |
| Transmission | Hydraulic Marine Gear |
| Dry weight | 640 kg (1411 lbs) |
| Flywheel housing | SAE 3 |
| Steering | Electronic Control compatible |
| Coolant capacity | 20L |
| Exhaust system | Water cooled manifold |
| Cooling system | Heat Exchanger |
| Lubrication | Forced lubrication |
| Oil capacity | 18L |
| Emissions rating | EPA Tier 2, RCD I, IMO compliant |
Yanmar 6LY3-STP Service & Performance Guide
What is the fuel consumption of the Yanmar 6LY3-STP?
The 6LY3-STP consumes approximately 22.1 gallons per hour at its maximum 3,300 RPM. This 440 HP version of the 5.8-liter block is tuned for higher power density in performance-oriented hulls. Maintaining a cruise at 2,500 RPM provides a significant boost in fuel range for offshore fishing trips.
What oil grade is required for the Yanmar 6LY3-STP?
This high-output engine requires 20.1 quarts of SAE 15W-40 oil satisfying API Service Class CI-4. The increased horsepower generates additional internal heat, making high-quality lubricant essential for turbocharger bearing life. Replace the oil and primary lube filter every 250 hours to ensure maximum engine longevity.
How does the Yanmar 6LY3-STP cooling system operate?
The system uses a freshwater cooling loop with a high-capacity heat exchanger and seawater-cooled intercooler to manage induction air. This setup allows the engine to maintain peak power in warm tropical waters without de-rating performance. Periodically flush the seawater side with freshwater to prevent salt buildup in the narrow exchanger tubes.
What are the electrical system specifications for this engine?
Standard units feature a 12V-80A alternator, integrated with Yanmar’s electronic control system for precision throttle and shift response. This output is sufficient for standard electronics, though high-draw vessels may require an auxiliary charging system. Maintain clean electrical grounds to the block to prevent EVC signal interference during high-speed transit.
What are the physical dimensions and weight of the 6LY3-STP?
The 6LY3-STP weighs 1,411 lbs, measuring 51.2 inches long and 27.6 inches wide. Its narrow inline-six design facilitates easy side-by-side installation in mid-sized cruisers. Ensure at least 4 inches of overhead clearance is available for removing the air filter housing and inspecting the turbocharger.
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