Volvo Penta TMD31L: Reliable Inboard Diesel Propulsion The Volvo Penta TMD31L is a robust, 4-stroke inline-4 cylinder diesel engine engineered for dependable inboard marine propulsion, delivering consistent power for a wide range of vessels navigating coastal and offshore waters. Key technical specifications underscore its balanced design: with a displacement of 2,400 cm³ (2.4 liters), it produces 100 horsepower at a maximum of 3,800 RPM, translating to 90 horsepower at the propeller shaft via the integrated HS1 high-slip transmission for smooth torque delivery. Weighing 400 kg (881 lbs) and measuring 1,150 mm in length, 669 mm in width, and 738 mm in height, the TMD31L offers an impressive power-to-weight ratio of approximately 4.17 kg/hp. It features a mechanical injection fuel system, corrosion-resistant aluminum block construction with stainless steel components, and an efficient oil cooling system to maintain optimal temperatures under load. Compliant with EU Stage III emissions standards, it minimizes NOx and particulate output while ensuring reliable combustion. Marine-specific benefits make the TMD31L a standout choice: its impeller-optimized water cooling system combats saltwater corrosion and overheating, while the compact layout facilitates seamless integration into tight engine bays. The inline-4 configuration reduces vibration for quieter operation, enhancing onboard comfort, and its durable build withstands harsh environments with low-maintenance accessibility for filters, belts, and service points. Performance-wise, the engine excels in fuel efficiency and torque at lower RPMs, ideal for sustained cruising or heavy loads in rough seas, with minimal drivetrain wear from the HS1 transmission. This versatility suits applications such as fishing trawlers, pleasure crafts, small ferries, and recreational boats, where balanced power, eco-compliance, and ease of installation drive operational reliability. Trusted by boatbuilders worldwide, the TMD31L embodies Volvo Penta’s legacy of engineering excellence for enduring marine performance. (248 words)