don't most cruising boats have vents. I have 2 cowl vents.

Cowl vents probably wouldn't do well at feeding a fire, but that's a good
point. I was also thinking of the vents for the engine. Some T37's have
replaced the dorades with Nicro vents as well.
As I said, closing the hatch MIGHT snuff the fire. At the very least it would
buy you time and that's the whole point if you can't fight the fire properly.
Leaving the companionway hatch open will just hasten the flames.

RB