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Yanmar 6LY400 – Marine Diesel Engine 400 HP
Yanmar 6LY400 – 400 HP utilizes a robust 5.8L inline-six marine diesel architecture designed for sustained reliability in offshore environments. This 400 HP model features a high-output 125-amp alternator and the latest VC20 vessel control system, providing the electrical capacity and digital precision required for modern on-board navigation, stabilization, and sonar arrays.
- Precision Operational Data: Rated at 400 HP (294 kW) at 3300 RPM.
- Internal Engine Configuration Type: Inline 6-Cylinder 5.81L Common Rail.
- Advanced Fuel Delivery System: Electronic Direct Injection with Digital Monitoring.
- Recommended Vessel Application Use: Engineered for mid-sized offshore yachts and workboats.
- Factory Protection Service Plan: Yanmar global marine service network support.
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Description
Yanmar 6LY400 400 HP – Advanced Common Rail Marine Propulsion
Maximizing power density in narrow engine compartments is the primary mechanical challenge solved by the Yanmar 6LY400. Delivering a formidable 400 HP at 3300 RPM, this 5.8-liter in-line 6-cylinder engine utilizes a high-pressure common-rail fuel system to provide instantaneous throttle response and reduced vibration for American offshore cruisers. Its compact footprint is specifically engineered for twin-engine installations in medium-sized sportfishing vessels where maximizing deck space is a priority for USA captains.
Adhering to strict EPA Tier 3 emission standards, the 6LY400 employs a 24-valve cylinder head and advanced electronic management to ensure smoke-free operation and superior fuel economy. For the American boater, this engine integrates seamlessly with NMEA 2000 networks, providing real-time digital diagnostics on modern helm displays. The robust freshwater cooling system is designed to withstand high-salinity conditions from the Gulf of Mexico to the Atlantic seaboard, ensuring long-term internal protection against galvanic corrosion.
Core Technical Specifications
- Maximum Output: 400 HP at 3300 RPM.
- Displacement: 354 cubic inches (5.808 Liters).
- Configuration: 6-cylinder in-line, 4-stroke diesel.
- Aspiration: Turbocharged with liquid-cooled intercooler.
- Dry Weight: Approximately 1164 lbs (engine only).
- Electrical: 12V / 125A high-output alternator.
- Compliance: Fully certified EPA Tier 3 standards.
- Bore and Stroke: 4.17 x 4.33 inches.
Yanmar 6LY400 Full Specs
| Engine type | In-line 6, 4-stroke Diesel |
| Displacement | 5.813L (354 cid) |
| Bore x stroke | 106 x 110 mm |
| Horsepower | 400 hp (294 kW) |
| Rated rpm | 3300 rpm |
| Aspiration | Turbocharged & Intercooled |
| Compression ratio | 16.4:1 |
| Fuel system | Common Rail Injection |
| Recommended fuel | Diesel (EN 590) |
| Ignition/Firing Order | Compression / 1-5-3-6-2-4 |
| Alternator | 12V, 125 Amp |
| Gear ratio/Drive | KMH61A / KMH61V |
| Transmission | Hydraulic Marine Gear |
| Dry weight | 585 kg (1290 lbs) |
| Flywheel housing | SAE 3 |
| Steering | VC10 Electronic Vessel Control |
| Coolant capacity | 20L |
| Exhaust system | Fresh water cooled manifold |
| Cooling system | Heat Exchanger |
| Lubrication | Pressure lubrication |
| Oil capacity | 19L |
| Emissions rating | EPA Tier 3, RCD II, IMO II |
Yanmar 6LY400 Service & Performance Guide
What is the fuel consumption of the Yanmar 6LY400?
The 6LY400 consumes approximately 20.2 gallons per hour at its maximum 3,300 RPM. This 5.8-liter inline-six common-rail engine is designed for high-speed planing hulls requiring rapid acceleration. For maximum cruising range, 2,500 RPM provides an optimal balance between fuel economy and maintaining consistent hull speed.
What oil grade is required for the Yanmar 6LY400?
This engine requires 20.1 quarts of SAE 15W-40 oil meeting API Service Class CJ-4 or higher specifications. High-pressure common-rail systems demand superior oil filtration to protect the precision fuel injectors from carbon buildup. Replace the oil and specialized filters every 250 hours to maintain full factory warranty coverage.
How does the Yanmar 6LY400 cooling system operate?
It features a closed-loop freshwater system with a high-capacity heat exchanger and seawater-cooled aftercooler. This ensures stable intake air temperatures, which is critical for the 24-valve head's combustion efficiency. Regularly inspect the seawater pump impeller and clean the oil cooler to prevent thermal stress during high-load operations.
What are the electrical system specifications for this engine?
Standard 6LY400 units come with a 12V-125A alternator, providing robust power for modern NMEA 2000 electronics and house banks. This system is fully integrated with Yanmar’s digital displays for real-time monitoring of engine health. Ensure all wiring connections are corrosion-resistant to prevent voltage drops in a saltwater environment.
What are the physical dimensions and weight of the 6LY400?
The dry weight is 1,296 lbs, measuring 51.3 inches in length and 30.6 inches in width. Its slim inline configuration makes it perfect for twin-engine setups in narrow-beam sportfishing vessels. Allow for 6 inches of service clearance around the turbocharger for routine inspections and maintenance access.
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