Radiator cap failure

[northern]

Just for information
Boat was using about a quart of antifreeze every 10 hours. The over flow bottle level did not change. Turned out rad cap had failed. Never seen one fail before.

 

[JHornsby3]

That is why it's best to replace them every few years. Just like the T stats. It's amazing what a simple thing like a cap can cause so many problems.