What is the ideal height above waterline for cooling water to exit the thru-hull?

The ideal height above the waterline for cooling water to exit the thru-hull is 6 inches. This measurement is based on balancing effective cooling intake with the intercepting of water that could be influenced by wave action or vessel movement. Placing the exit point at this height ensures that the cooling water can be efficiently drawn in by the pump during normal operation while minimizing the risk of air getting into the system, which can occur if the exit point is too close to the waterline.

When the exit is positioned at a height of 6 inches above the waterline, it helps to ensure that there is a constant supply of water available for cooling even in varying conditions, such as swells or when the boat is at rest. This design consideration is crucial for maintaining optimal engine temperatures and preventing overheating, which can lead to mechanical failure.