Yanmar 4LHA-STP – Inboard Marine Diesel Engine 240 HP

The Yanmar 4LHA-STP provides a verified heavy-duty mechanical injection configuration for demanding offshore applications. Producing 240 horsepower at 3300 RPM, this 3.455-liter diesel prioritizes raw reliability over complex electronic systems. A dedicated turbocharger manages intake air density during continuous commercial workloads consistently. Forced enclosed lubrication utilizes an 11-liter oil sump. This actively protects moving components across varying dynamic operational loads. It eliminates the need for delicate digital air management sensors inside harsh saltwater environments while maintaining highly responsive throttle performance across mid-range speeds.

Isolating the internal block from the ocean, an 11.5-liter freshwater coolant circuit regulates operating temperatures safely. Raw seawater stays completely outside the internal engine cylinder waterways. This permanently prevents internal salt scaling and heavy metal corrosion inside the cast block. The native SAE 4 flywheel housing mounts seamlessly to HSW450A hydraulic marine gears. Auxiliary electrical systems rely on the standard 12V 60-amp alternator output. Total dry weight registers at exactly 365 kg. Repower mechanics must factor this physical mass into rear hull displacement calculations.

Engine Operation and Output

Relying purely on mechanical fuel regulation, this 3.455-liter Yanmar engine provides exceptional physical reliability in remote operating locations. An 11-liter oil sump ensures forced pressure lubrication during demanding continuous commercial runs. The rugged mechanical injection setup satisfies stringent IMO Tier II emissions limits globally. This happens by utilizing an 18.4:1 compression ratio across the 1-3-4-2 firing order. Throttle synchronization runs directly through traditional mechanical push-pull cable linkages. This ensures immediate physical response during tight marina docking maneuvers and rapid heavy-duty shifting requirements under extreme load.

Why Choose the Yanmar 4LHA-STP Inboard Diesel Engine

Heavy-duty operators select the 4LHA-STP inboard diesel engine for its substantial 3.455-liter displacement and dependable 240 horsepower output. Mechanical direct injection provides remarkably rugged running conditions compared to modern digitally governed units. Featuring a reliable 60-amp alternator, it effectively sustains basic DC circuits and essential navigation screens. The SAE 4 flywheel housing adapts immediately to HSW450A hydraulic transmissions or heavy HSW630A gears. Total dry weight remains strictly at 365 kg. This minimizes drastic center of gravity shifts inside your commercial vessel’s primary engine room.

Warranty and Support

Yanmar protects this 3.455-liter propulsion block with a standard Limited Factory Warranty covering major internal assembly defects comprehensively. provides essential product-information support before purchase and technical assistance with order-related questions. A thorough pre-shipment visual inspection confirms the crated engine item and all documented included components. Mechanics and vessel owners should examine warranty coverage scope concerning specific commercial versus recreational duty cycles. Please review the detailed warranty coverage and eligibility details directly on before placing your final heavy freight purchase order definitively.

Before Ordering the Yanmar 4LHA-STP Inboard Diesel Engine

Confirm your engine room hatch opening carefully to guarantee adequate fitting clearance for this 365 kg block. You must verify your intended transmission reduction gear ratio and existing shaft coupling dimensions. Check that your onboard DC wiring system safely supports a 12V 60-amp alternator charging circuit output. Next, confirm whether your helm station supports required mechanical push-pull cables versus modern electronic control inputs. Ensure your existing diesel fuel filtration system matches the precise ISO 8217 DMA flow demands for mechanical direct injection networks smoothly.