When should you drain your engine of water, besides during cold weather?

[farrisoip]

I just bought a 22I and am wondering when I should drain the water out of the engine? If it is going to sit for a week or two is it best to drain or does it not matter? Thanks

[hanzj]

I have never drained the water from the engine of any of my boats, except when winterizing. It isn't necessary if you are running in freshwater.

[wolfpack]

Draining the water promotes rust.