You can break it down into the three components and inspect them. What is most important is that the head (top unit) is in good shape and does not have a lot of oxidation - Al oxide white powder under the paint eating away the Aluminum, especially if it starts to infringe on the seal area. I replaced both of mine because of this. The filter element itself should be replaced periodically and should be if it is used and been sitting. The Al water separator section at the bottom is the model designed for being installed in motor compartments with inboard motors for safety but is not as convenient as the clear plastic one for outboards that you can glance at quickly from the outside and see if it needs to have the water drained. I would check it for Al oxidation also. As I understand it, you can use an Al water separator in place of a plastic one but not the other way around in terms of the correct safe application (no plastic separator in the inboard motor compartment).