When you say "low pressure", you really mean "low flow", right? There is normally a "pump saver" screen strainer installed just upstream of the fresh water pump. It's not a filter, so does not clog easily, but if it's never been cleaned out, sometimes this causes low flow. This will look like a large lawnmower fuel filter, so just an inline bulge in the inlet line with a hard, clear plastic body which can be unscrewed after removing from the line. Undo the body, and you will find a mesh screen, like a window screen which can be washed. Alternatively, back-flush the screen while still installed in the strainer to avoid disassembly. Other than that, aerators, old pump with missing impeller blades, pulling air? Depending on the pump age, you may be able to disassemble and replace parts of the fresh water pump without replacing the electric motor itself - depending on how handy you are.