Troubleshooting lack of water pressure

[TopherTO]

Water pressure on my boat seems to be decreasing slowly overtime, and I'm trying to wrap my head around how to increase it. The pump is a Jabsco Par-max 3.5 with a pressure switch that cuts in at 20 psi and out at 40 psi (according to the manual). The accumulator is a Shurflo 182-200. I've read that the accumulator should be pumped to the same pressure as the water pumps cut in pressure (20 psi in this case). Instructions I read for checking and topping up the accumulator pressure are to turn off power to the pump, open a faucet and pump the accumulator to the appropriate pressure (20 psi), which I've done. Very disappointed to see that this didn't make a difference. Any suggestions on why this may be and how I can increase the pressure?

[Bowdrie]

The pump "is what it is", its pressures for cut-in/cut-out are not going to change.
The little accumulator tank only has a total volume, air/water of ~21 ounces.
In real life it holds little more than a cup of water.
It's designed just to take some of the pulsation out of the flow.
https://www.pentair.com/content/dam/...r-tank-iom.pdf

[TopherTO]

UPDATE FROM OP: I just tested connecting the water pump to an alternative water supply and have the same low pressure. Which I think rules out a partial clog or kink in the water supply... 🤷*♂️