There are several exceptions to having to pay Maine's sales or use tax on your boat. Somebody mentioned the 30-day rule, but if you purchased the boat out of state, were not a resident of the state at the time of purchase, and registered and used the boat out of state for more than a year there is no sales or use tax due if you subsequently keep the boat in Maine. There is an annual excise tax that will come due, but it is based on boat age, length, and I believe horsepower and not strictly on value. It can be pretty modest if your boat is older. Every state gets their taxes, just in different ways.