Depending on the type of boat that you have, you have to think about what kind of maintenance supplies you will need for that boat. For instance, the type of items that you would need to maintain a sailboat would be very different from what you would need to perform maintenance on a motorboat.
With my boat, I’ve got a 2 stroke engine, so it’s important that I always have a decent stock of 2 stroke oil. The oil is mixed in with the fuel when you’re using it, so it’s different from the oil that would be used on other types of boats. Of course, with a sailboat, you wouldn’t use oil at all, but you’d have a very different boating experience.