Just go title it in your name and the buyer will be put at ease, and you will avoid future hassles.
In states that issue titles, the title indicates ownership.
Registration is merely your permit to use it on the water.
When you register it, then you have shown you paid the taxes to use in the state of registration, if it has not been used, then no taxes are due. To sell all you need is the correct documentation to show you own it, either by title in your name or a title that has been signed off by the previous owner in hand, once it is signed, it has become a bearer document and whom ever possesses the document owns the item described on the title. Registration and Title are two separate situations, when you buy a car the owner of the contract is shown on the title as the lien holder, in other words they have an ownership interest in joint with you, but they are not shown on the registration, the registration shows you are an owner and you as the owner have paid the use taxes on the vehicle. When you paid the vehicle off, then the joint owner, issues a lien release and you own the vehicle. When an owner signs a title they have released all interest in the vehicle and anyone holding that title is the owner of the the vehicle and has right to dispose of as he/she sees fit.
When the registration has been paid, then you are able to use in the state the item is registered in, what is really complicated, is when another state decides they won't honor the registration, we had this happen a few years ago, between the state of Montana and Idaho, the state of Idaho, would not honor our Montana registrations for a period of 9 days, due to a dispute between our Governors, we called it a little boys pissing match! but people were getting stopped in both states and given $1.00 tickets because the vehicles were not registered in the state they were operating in!