I am just off out,
but perhaps you could give me a call tomorrow to discuss
be aware that cutting extra vent holes in the engine box will really increase the engine noise inside the boat.
a problem I lived with on my last boat, but she never did the long trips you do.
if you can feed in air through a blower and let it vent overboard it should be a better option, but you need to think of sound deadening as well as reducing the air temp inside the engine box.
Charlie