The 24x7 stainless steel Nicro 2000 solar vents are very popular with boaters. We had one on our last sailboat. They don't move enough air to have a cooling effect, but they do move enough to keep the carbon dioxide level from your breathing down when sleeping aboard and the boat is closed up over night (assuming some other air source in the boat) and they do help keep the humidity down and mildew growth at bay when the boat is closed up unused. They come with two interchangable blades, one for air intake and one for exhaust.
http://www.marinco.com
Linear Mode
