Sea Ray

Is pressure your problem or is it flow? Are you having the same problem at all taps? Have you tried measuring the flow by filling a 2 gal pal while timing it and run the same test on a similar boat in your marina? That will tell you if you have a flow problem or it is just the nature of your system. Have you removed and cleaned all aerators and screens on shower heads? If you still have the factory pump you may want to consider replacing with a new variable speed pump.

Is the issue both on the cold and hot sides? As Fwebster said, there is a small filter at the pump that is often overlooked. I have also had issues with calcium deposits that become lodged at 90 degree fittings. I have pulled fittings apart and removed deposits and have also run CLR through the systems to break up deposits. This is an aggressive fix that needs to be followed by several clean rinses. If you remove the filter at the pump and there is no shut off valve, make sure to drain the tank first.