The exhausts for the blowers are on the side of the hull, and point straight outward.
That would be bad, but what's worse is that Hatteras covered them with clamshells facing aft. These are fine when you're running (the spray is going the other way, and impacts on the clamshell without going inside) BUT when shut down and a nasty storm comes from ASTERN you get air - and water, if there's some entrained in it - blown up into the vents. That water then goes through the squirrel cage blowers and into the bilge.
It took me QUITE a while to figure out where it was coming from. I'd shop-vac the bilge DRY and it'd stay dry for a couple of weeks, then magically one day it would be WET! Always outboard of the stringers, from the forward ER bulkhead back to the main intakes. It drove me NUTS for over a year; I thought I had leaks at the main induction through-hull/seacocks (that would be BAD!) for a while, and on the port side I thought the head pump might be leaking (its over there on a shelf), but then why leak only SOMETIMES, and why sometimes was only one side wet?
Well, one night I was on board and a huge storm blew up. It was trying to rain through the aft salon door (without success) and I started thinking (I know, dangerous stuff.) Went below and voila - water was coming in - quite a bit of it - through the blowers! I was shocked at exactly how MUCH water can get in that way - in a really ugly storm over a couple of hours time it can amount to a gallon or so per side! With the "right" angle of wind and rain the hullside traps water, it runs up/across the hullside, into the clamshell and is blown into the boat.
Since its FRESH water it goes fetid almost instantly.
Anyway, I can't rotate the clamshells to any other "better" orientation - at least I don't think I can. Downward would be a disaster in heavy spray, as it could be driven up into the blower inlets. Up obviously doesn't work, and neither does forward. Aft is probably the best choice, but the general design for those blower exhausts just plain sucks, and leaves me with few options.
My first thought was to fit a dorade box between the blower and hullside, with an offset between in and outlet piping, and then plumb a drain to the centerline ER bilge, where the pump is. Now if it "rains" in the dorade box it drains into the sump instead of ending up in the bilge space proper. I could also plumb it overboard but I don't have an extra through-hull on the side of the hull handy for that.
The only other thing I can come up with is to stick a BIG blower on the port side aft near the induction intake that blows outward, and close off both blower exhausts on the hullsides. Then when I want a blower I run that; it blows air out the port side and since there's a vacuum air would be drawn in from the starboard side under-deck coaming. That would likely fix it, but it would take some engineering to work out a mount and take a BIG blower to be effective, since I can't block that uinder-deck inlet without restricting airflow to the engines when under way. That would likely require 120V blower wiring - that's not a disaster since I could use the existing 12V wiring to energize a relay.
