I own a 1985 43' CPMY Californian which, is the same as the 38' with a 5' cockpit on the stern. I looked at a number of 43's and the common problem was condition of the 400 gallon fuel tank. It sits under the queen bed in the aft stateroom. Definitely have it inspected because if it needs replacing, it has to be cut apart before being removed and can only be replaced with two, 200 gallon tanks, side by side. Fortunately, the one in mine was replaced by a previous owner.
Under the side walk decks are tanks. Their usage varies from boat to boat. Mine has a 50 gallon (estimated) tank under each side deck and is used for additional water storage and connects to the fresh water system. I saw one boat where one was converted to store additional fuel.
Good luck, Karl