Propeller Shaft Torque Calc

Repowering your boat and need to know if the existing shaft can handle more torque? Enter engine HP, RPM, and gear ratio to get required shaft diameter, torsional stress, and critical speed margin — so you avoid a broken shaft at sea. TORQUE CALCULATOR Enter engine horsepower, shaft RPM, and safety factor. Calculates required shaft torque, minimum shaft diameter, and torsional stress. Supports multiple shaft materials. SHAFT SIZE TABLE Reference table of common shaft diameters (3/4 to 4 inches) with maximum torque capacity for stainless steel and Monel. Includes recommended RPM ranges for each size. MATERIAL COMPARISON Compare marine shaft materials: 316 Stainless, Monel K-500, Aquamet 17, and Aquamet 22. Shows yield strength, fatigue limit, corrosion resistance, and typical applications side by side. CRITICAL SPEED Calculate critical shaft speed based on shaft length, diameter, and bearing spacing. Shows safety margin above operating RPM to avoid vibration resonance. Built for marine engineers, boat builders, and propulsion system designers. Works offline.