You're looking for an NPT bulkhead fitting probably in 3/8" NPT at least that's what mine is. I have a 4000 psi pressure washer so maybe not comparable.
https://www.highpressure.com/product...ead-couplings/
You could attach a pressure washer quick release to the bulkhead fitting and then figure out how you want to mount to deck or
cabin sides. Run a pressure washer hose from washer to the other side of bulkhead fitting. Enclose in some type of plastic
marine deck enclosure repurposed for a faucet or similar.
Most bulkhead fittings are not designed for high pressure, usually for drawing
water out of a tank to feed pressure washer. I looked around and brass seems to top out at 1000psi, 316 stainless goes up to 15k PSI which is way overkill but you get a fitting that wont corrode.
In practice my pressure washer quick connects need a shot of WD40 to keep the coupling mechanism limber. I have the same problem with my air system in my shop. I run a number of hard lines outside my shop so I can use air in driveway. I need to squirt
oil on them every few months so they don't stiffen up. I would think it would be much worse on a
boat with the
salt water.