If you take a new faucet screen
off (in the US) on the upstream side, you see a plastic bit with a 1/8" hole in it. That is for flow control (per plumbing
codes). The size is based on 80 psig pressure in a water
main. Boat systems generally run 30-40 psig.
The neat thing is if you put a small nail in the hole and pry sideways the plastic bit 9 times out of 10 pops off.
Loose the plastic flow restrictor and your pressure will be better.