How long should the throttle be set at full power while back flushing the engine?

Setting the throttle at full power for 3-5 seconds while back flushing the engine is essential for effectively clearing any debris or obstructions that may be present in the cooling system. This duration allows sufficient time for the water flow to create the necessary pressure needed to dislodge and expel any contaminants from the engine components.

Using this specific time frame ensures that the back flushing process is thorough enough without risking damage to the engine or compromising its performance. It strikes a balance between effective cleaning and avoiding excessive force that could lead to other issues. The options that suggest either shorter or longer durations may not provide optimal results or could potentially harm the engine's integrity. Thus, 3-5 seconds is the most appropriate and widely accepted duration for this maintenance procedure.