How hard is it to turn crank shaft manually?

Turning a crankshaft manually can vary in difficulty depending on several factors, including the engine size, the condition of the components, and whether the engine is in good working order. In general, a well-lubricated engine with no significant mechanical issues should allow for relatively smooth manual rotation, while a seized or damaged engine may be very challenging or impossible to turn. Additionally, larger engines tend to require more effort due to their increased mass and resistance. Proper tools and techniques can help ease the process.