Another point; we tried leaving the portholes open for ventilation during the week while away from the boat. We tried different angles, ie 45 degrees open, then about 22 degrees, but rain always got in. We eventuAlly gave up. Our portholes are the common Beckson brand with plastic frame and an acrylic
lens. The lens has a ridge around it for strength, but this ridge also holds water
which the wind
then blows inside the boat. Also, the way the hinges work, there is a gap between the cabin
wall and the porthole lens when the lens is in an open position. Rain or spray easily finds its way into this gap and inside the boat. I have even tried putting the lens near vertical , which gives maximum ventilation and less likely to scratch legs. However, spray or light rain runs off cabin roof, hits lens which diverts water
, you guessed it; inside the boat.
Initially one would think that an outward opening port would function like an awning, providing some shade and protection from rain. In reality, the way they are designed, an off the shelf mass produced ports
when mounted in an outward opening fashion actually encourages water getting into the boat. You would have to build a mini awning over each port, if one insisted on outward opening ports.