I live in Michigan, Do I need to Pay Taxes on the title transfer if I buy an out of state Boat.
I know that If I buy an item mailorder and that item comes from another state there is ( I want to say) no tax. Does the same apply to boats and/or Cars?

That could be a Sizable amount on 80-100k Boat.

A boat is more like a car. Typically you will pay the sales/excise tax to the state in which it will be registered. Like a car, sales tax is not paid to the dealer or seller, but to the state. When you go to register, that's when they get your money.

I have heard that some states do not charge sales tax on used boats, but I don't know what states.

I do taxes and related work for a living. I've also dealt with this myself. EACH STATE IS DIFFERENT. I keep the boat in OK and we have a house there, but I live in TX. I boat on Texoma which is on the border. In TX you have to pay sales tax on the purchase price of the boat. Oklahoma has a funny way of paying taxes. They take the purchase price when new and they depreciate the value over 8 years. I bought a 1992 in 2005 and it it cost like $20 to have them do a new OK title- so no tax. Oklahoma does not do used cars like this; they have a separate system for boats.

In Michigan, you will have to pay sales tax on the boat and trailer when you register it and apply for the title. If you buy from out of the state they will still get your money when you bring it home and register it. I bought a boat from Missouri (LOTO) a few years ago and it was registered with the Coast Guard. They don't have to have to register with the state then and can avoid paying a sales tax. No such luck for us in Michigan.