Welcome to the Socialist Peoples Republic of Maryland.
If you keep it in MD you will owe MD the 'differential' of sales tax
..... and you have 30 days to pay it as the tax clock starts running the
instant you enter MD. 1 second over the dwell/entry period and you get
hefty penalties with interest applied.
If you keep the boat in VA and only occasionally visit MD then you owe
VA. It all depends on which state is the state of 'principal usage'.