Sales tax varies from state to state. Sales tax is what is called a “transactional tax.” The tax is paid on the transaction rather than on the item. Each time the item is sold, the transaction is taxed. Having said that, some transactions are non-taxable, depending on the state. For example, some states may only tax the trailer, etc.
In Nebraska, a boat and motor together is considered a vehicle and the sales tax is paid when you register it at your local courthouse. If you buy a boat or a motor separately, you pay sales tax where you take possession (dealership for example) If it is a private party, you are supposed to file a Use Tax Return, which is the equivalent to Sales Tax.
If you do pay sales tax to another state and the transaction is taxable in your state, you should be able to get credit for the taxes paid with proper documentation. The 2 states will then hash it out.
JD