Putting in a freshwater pressure faucet system is a little different than what you have at the moment, which is a hose from the spigot going to a foot pump and sucking water from a hose going to the water tank. To install a pressure water system you need to add a "tee" fitting to the existing hose BEFORE IT GETS TO THE FOOT PUMP. This tee will then connect to a pressure water pump intake port. On the other side of the pressure water pump you need a hose capable of withstanding the pressure of the water pump (reinforced vinyl hose or polyethylene plumbing
systems). Then that hose connects to a faucet. The pump will require 12 volt electricity from a circuit that has a fuse or circuit breaker to protect you from overheating
wires resulting from a short circuit or overwhelmed pump. This is not rocket science, just ask the store supplying the pump to show you what the current
requirements are for your selected pump. With respect to that aspect, some pumps deliver smaller amounts of water using less pressure, others can blast water out for the fire department. On a small boat you should probably look for the smaller flow to conserve electricity, purchase
cost and available water in your tank. Adding an "accumulator tank" is pretty simple and allows the pump to produce consistent pressure, without high and low spots, as well as make the pump live longer and happier. It can be added at a later time, if you wish, for economy. You can make the system more complicated, costly and versatile by installing the electric
pump near the water tank and running other hoses (via tees and valves) to additional sinks, shower
and water heater units, but in a 28 footer this might be overkill.