You’re in PA? If your boat is used in PA, it must be taxed and registered there. If it is not ever going to be in PA, you will not be taxed. Most states go by “state of principal use” in determining where it must be registered and subject to tax.
If you register your boat in another state, you might expect a friendly letter from PA Revenue starting out, “Hey looks like you bought yourself a boat...” If so, you’ll need to tell them the boat was never in PA and submit a marina slip contract to prove it.
However, if your boat subsequently ever slides across the line into PA however briefly, you will be on the hook for the PA tax.