You are right. Better yet do not have a cast screen on the outside, as it's a proven place for marine life to grow. We do have a Groco strainer inside to catch seaweed.That's kinda wrong. I've had my Pearson 10M (gone in Irmaria after I sold it) surfing down waves and clicking 10kn. I know better than to be forcing a water column into my 2 cyl. Yanmar 2YM20 at speed with the thru hull valve wide open. I called Groco on this a few years ago. On a sailboat, the slits face aft. But nobody does it.