Depending on the size of your boat the systems could include the head, water galley and electrical components, all of which need to be inspected, cleaned and tested.
If your head is a portable system the checking is pretty simple, make sure the tank is cleaned out, you have chemicals on board and it works.
If your have a permanent systems, it’s really not much different. The system need to be cleaned and lubricated for smooth operations. The tanks need to be cleaned and maybe even flushed if possible. If you have chemical treatments make sure you have a supply on board and accessible. If you have to have your own dump hose for the marina, make sure it’s accessible and not damaged or leaking.
One other thing, if your boat has a Y-valve make sure it is working, labeled for the correct operation and secured in the appropriate position.
The water system is pretty basic. The storage tank needs to be flushed to clean it out. If it was sitting with water in it, you’ll need to run a sanitizer through it. In fact, you should sanitize the tanks even if you had antifreeze in it. Using a pool or spa chlorine will remove bacteria and clean the tank. Once you add the chlorine to the tank, let it sit for a while and then run the water through the system so that the chlorine gets a chance to pass through all the fixtures and drains.
While running the chlorinated water through the system; inspect the hoses, clamps and pumps for leaks. At the same time you can test the water heater to make sure it works. But remember; don’t run the water heater without water in it.
After testing the water system you should inspect clean and operate the refrigerator, freezer, stove and any other appliances. Depending on your individual situation, this might include operating the appliances on the shore power, battery power or “gas” (like propane). Any gas fittings should be inspected for dirt, damage and leakage. A small bottle of bubble blowing liquid works great to find leaks in gas line fittings.
The electrical system inspection and preparation can be quite extensive depending on your specific boat. Typically you’ll have batteries that need to be inspected and charged.
If you have a fishing boat you may have the addition of a cleaning station and live wells. The live wells should be checked for operation and leakage. Many boats also have a deck fresh water shower or spray system that needs to be tested.