Ford Lehman 2725 Marine Engine: Reliable Inboard Propulsion for Demanding Seas The Ford Lehman 2725 is a robust inboard diesel engine engineered for marine propulsion, delivering dependable power to drive boats through diverse waterway conditions. Renowned for its workhorse reliability, this engine transforms diesel fuel into efficient thrust, making it a staple in both commercial and recreational vessels. Key technical specifications underscore its engineering prowess: an inline-6 cylinder configuration with a displacement of 6.22 liters (6,220 cm³), featuring a 107 mm bore and 115 mm stroke for a long-stroke, undersquare design (bore-stroke ratio of approximately 0.92). The high compression ratio of 16.1:1 optimizes combustion efficiency, while cast-iron construction ensures longevity in harsh environments. As an inboard drive system, it integrates seamlessly with gear or belt-driven transmissions to transfer power directly to the propeller shaft. Marine-specific benefits elevate the 2725’s suitability for saltwater and freshwater operations. Its corrosion-resistant components withstand exposure to seawater, minimizing wear from electrolysis and biofouling. The inline-6 layout promotes inherent balance, reducing vibration and noise for smoother underway performance and enhanced crew comfort. Inboard mounting at the vessel’s centerline improves hydrodynamic stability, mitigating roll and heave while shielding the powerplant from external impacts like debris or waves. Additionally, its closed-loop or raw-water cooling systems, when properly maintained, prevent overheating in tropical climates or during prolonged idling. Performance characteristics emphasize torque optimization over high-revving speed, with peak output at lower RPMs ideal for hull speed maintenance, heavy loading, and precise maneuvering. This yields impressive thermal efficiency—around 40%—translating to superior fuel economy and extended range on long passages, without the ignition vulnerabilities of gasoline counterparts. While emissions may require modern aftertreatment for regulatory compliance, the engine’s diesel heritage ensures clean, consistent power delivery. The Ford Lehman 2725 excels in applications demanding versatility and endurance, such as trawlers, workboats, and mid-sized yachts. Whether navigating coastal fisheries, supporting offshore supply runs, or powering leisure cruises, it provides the torque-heavy propulsion needed for reliable, efficient voyaging in challenging marine realms.